<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/arch/powerpc/include, branch v5.5</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>powerpc/mm/hash: Fix sharing context ids between kernel &amp; userspace</title>
<updated>2020-01-23T10:26:20+00:00</updated>
<author>
<name>Aneesh Kumar K.V</name>
<email>aneesh.kumar@linux.ibm.com</email>
</author>
<published>2020-01-08T05:44:22+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5d2e5dd5849b4ef5e8ec35e812cdb732c13cd27e'/>
<id>5d2e5dd5849b4ef5e8ec35e812cdb732c13cd27e</id>
<content type='text'>
Commit 0034d395f89d ("powerpc/mm/hash64: Map all the kernel regions in
the same 0xc range") has a bug in the definition of MIN_USER_CONTEXT.

The result is that the context id used for the vmemmap and the lowest
context id handed out to userspace are the same. The context id is
essentially the process identifier as far as the first stage of the
MMU translation is concerned.

This can result in multiple SLB entries with the same VSID (Virtual
Segment ID), accessible to the kernel and some random userspace
process that happens to get the overlapping id, which is not expected
eg:

  07 c00c000008000000 40066bdea7000500  1T  ESID=   c00c00  VSID=      66bdea7 LLP:100
  12 0002000008000000 40066bdea7000d80  1T  ESID=      200  VSID=      66bdea7 LLP:100

Even though the user process and the kernel use the same VSID, the
permissions in the hash page table prevent the user process from
reading or writing to any kernel mappings.

It can also lead to SLB entries with different base page size
encodings (LLP), eg:

  05 c00c000008000000 00006bde0053b500 256M ESID=c00c00000  VSID=    6bde0053b LLP:100
  09 0000000008000000 00006bde0053bc80 256M ESID=        0  VSID=    6bde0053b LLP:  0

Such SLB entries can result in machine checks, eg. as seen on a G5:

  Oops: Machine check, sig: 7 [#1]
  BE PAGE SIZE=64K MU-Hash SMP NR_CPUS=4 NUMA Power Mac
  NIP: c00000000026f248 LR: c000000000295e58 CTR: 0000000000000000
  REGS: c0000000erfd3d70 TRAP: 0200 Tainted: G M (5.5.0-rcl-gcc-8.2.0-00010-g228b667d8ea1)
  MSR: 9000000000109032 &lt;SF,HV,EE,ME,IR,DR,RI&gt; CR: 24282048 XER: 00000000
  DAR: c00c000000612c80 DSISR: 00000400 IRQMASK: 0
  ...
  NIP [c00000000026f248] .kmem_cache_free+0x58/0x140
  LR  [c088000008295e58] .putname 8x88/0xa
  Call Trace:
    .putname+0xB8/0xa
    .filename_lookup.part.76+0xbe/0x160
    .do_faccessat+0xe0/0x380
    system_call+0x5c/ex68

This happens with 256MB segments and 64K pages, as the duplicate VSID
is hit with the first vmemmap segment and the first user segment, and
older 32-bit userspace maps things in the first user segment.

On other CPUs a machine check is not seen. Instead the userspace
process can get stuck continuously faulting, with the fault never
properly serviced, due to the kernel not understanding that there is
already a HPTE for the address but with inaccessible permissions.

On machines with 1T segments we've not seen the bug hit other than by
deliberately exercising it. That seems to be just a matter of luck
though, due to the typical layout of the user virtual address space
and the ranges of vmemmap that are typically populated.

To fix it we add 2 to MIN_USER_CONTEXT. This ensures the lowest
context given to userspace doesn't overlap with the VMEMMAP context,
or with the context for INVALID_REGION_ID.

Fixes: 0034d395f89d ("powerpc/mm/hash64: Map all the kernel regions in the same 0xc range")
Cc: stable@vger.kernel.org # v5.2+
Reported-by: Christian Marillat &lt;marillat@debian.org&gt;
Reported-by: Romain Dolbeau &lt;romain@dolbeau.org&gt;
Signed-off-by: Aneesh Kumar K.V &lt;aneesh.kumar@linux.ibm.com&gt;
[mpe: Account for INVALID_REGION_ID, mostly rewrite change log]
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20200123102547.11623-1-mpe@ellerman.id.au
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Commit 0034d395f89d ("powerpc/mm/hash64: Map all the kernel regions in
the same 0xc range") has a bug in the definition of MIN_USER_CONTEXT.

The result is that the context id used for the vmemmap and the lowest
context id handed out to userspace are the same. The context id is
essentially the process identifier as far as the first stage of the
MMU translation is concerned.

This can result in multiple SLB entries with the same VSID (Virtual
Segment ID), accessible to the kernel and some random userspace
process that happens to get the overlapping id, which is not expected
eg:

  07 c00c000008000000 40066bdea7000500  1T  ESID=   c00c00  VSID=      66bdea7 LLP:100
  12 0002000008000000 40066bdea7000d80  1T  ESID=      200  VSID=      66bdea7 LLP:100

Even though the user process and the kernel use the same VSID, the
permissions in the hash page table prevent the user process from
reading or writing to any kernel mappings.

It can also lead to SLB entries with different base page size
encodings (LLP), eg:

  05 c00c000008000000 00006bde0053b500 256M ESID=c00c00000  VSID=    6bde0053b LLP:100
  09 0000000008000000 00006bde0053bc80 256M ESID=        0  VSID=    6bde0053b LLP:  0

Such SLB entries can result in machine checks, eg. as seen on a G5:

  Oops: Machine check, sig: 7 [#1]
  BE PAGE SIZE=64K MU-Hash SMP NR_CPUS=4 NUMA Power Mac
  NIP: c00000000026f248 LR: c000000000295e58 CTR: 0000000000000000
  REGS: c0000000erfd3d70 TRAP: 0200 Tainted: G M (5.5.0-rcl-gcc-8.2.0-00010-g228b667d8ea1)
  MSR: 9000000000109032 &lt;SF,HV,EE,ME,IR,DR,RI&gt; CR: 24282048 XER: 00000000
  DAR: c00c000000612c80 DSISR: 00000400 IRQMASK: 0
  ...
  NIP [c00000000026f248] .kmem_cache_free+0x58/0x140
  LR  [c088000008295e58] .putname 8x88/0xa
  Call Trace:
    .putname+0xB8/0xa
    .filename_lookup.part.76+0xbe/0x160
    .do_faccessat+0xe0/0x380
    system_call+0x5c/ex68

This happens with 256MB segments and 64K pages, as the duplicate VSID
is hit with the first vmemmap segment and the first user segment, and
older 32-bit userspace maps things in the first user segment.

On other CPUs a machine check is not seen. Instead the userspace
process can get stuck continuously faulting, with the fault never
properly serviced, due to the kernel not understanding that there is
already a HPTE for the address but with inaccessible permissions.

On machines with 1T segments we've not seen the bug hit other than by
deliberately exercising it. That seems to be just a matter of luck
though, due to the typical layout of the user virtual address space
and the ranges of vmemmap that are typically populated.

To fix it we add 2 to MIN_USER_CONTEXT. This ensures the lowest
context given to userspace doesn't overlap with the VMEMMAP context,
or with the context for INVALID_REGION_ID.

Fixes: 0034d395f89d ("powerpc/mm/hash64: Map all the kernel regions in the same 0xc range")
Cc: stable@vger.kernel.org # v5.2+
Reported-by: Christian Marillat &lt;marillat@debian.org&gt;
Reported-by: Romain Dolbeau &lt;romain@dolbeau.org&gt;
Signed-off-by: Aneesh Kumar K.V &lt;aneesh.kumar@linux.ibm.com&gt;
[mpe: Account for INVALID_REGION_ID, mostly rewrite change log]
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20200123102547.11623-1-mpe@ellerman.id.au
</pre>
</div>
</content>
</entry>
<entry>
<title>powerpc/xive: Discard ESB load value when interrupt is invalid</title>
<updated>2020-01-22T09:31:41+00:00</updated>
<author>
<name>Frederic Barrat</name>
<email>fbarrat@linux.ibm.com</email>
</author>
<published>2020-01-13T13:01:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=17328f218fb760c9c6accc5b52494889243a6b98'/>
<id>17328f218fb760c9c6accc5b52494889243a6b98</id>
<content type='text'>
A load on an ESB page returning all 1's means that the underlying
device has invalidated the access to the PQ state of the interrupt
through mmio. It may happen, for example when querying a PHB interrupt
while the PHB is in an error state.

In that case, we should consider the interrupt to be invalid when
checking its state in the irq_get_irqchip_state() handler.

Fixes: da15c03b047d ("powerpc/xive: Implement get_irqchip_state method for XIVE to fix shutdown race")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Frederic Barrat &lt;fbarrat@linux.ibm.com&gt;
[clg: wrote a commit log, introduced XIVE_ESB_INVALID ]
Signed-off-by: Cédric Le Goater &lt;clg@kaod.org&gt;
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20200113130118.27969-1-clg@kaod.org
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
A load on an ESB page returning all 1's means that the underlying
device has invalidated the access to the PQ state of the interrupt
through mmio. It may happen, for example when querying a PHB interrupt
while the PHB is in an error state.

In that case, we should consider the interrupt to be invalid when
checking its state in the irq_get_irqchip_state() handler.

Fixes: da15c03b047d ("powerpc/xive: Implement get_irqchip_state method for XIVE to fix shutdown race")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Frederic Barrat &lt;fbarrat@linux.ibm.com&gt;
[clg: wrote a commit log, introduced XIVE_ESB_INVALID ]
Signed-off-by: Cédric Le Goater &lt;clg@kaod.org&gt;
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20200113130118.27969-1-clg@kaod.org
</pre>
</div>
</content>
</entry>
<entry>
<title>powerpc/spinlocks: Include correct header for static key</title>
<updated>2019-12-30T10:20:41+00:00</updated>
<author>
<name>Jason A. Donenfeld</name>
<email>Jason@zx2c4.com</email>
</author>
<published>2019-12-23T13:31:47+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=6da3eced8c5f3b03340b0c395bacd552c4d52411'/>
<id>6da3eced8c5f3b03340b0c395bacd552c4d52411</id>
<content type='text'>
Recently, the spinlock implementation grew a static key optimization,
but the jump_label.h header include was left out, leading to build
errors:

  linux/arch/powerpc/include/asm/spinlock.h:44:7: error: implicit declaration of function ‘static_branch_unlikely’
   44 |  if (!static_branch_unlikely(&amp;shared_processor))

This commit adds the missing header.

mpe: The build break is only seen with CONFIG_JUMP_LABEL=n.

Fixes: 656c21d6af5d ("powerpc/shared: Use static key to detect shared processor")
Signed-off-by: Jason A. Donenfeld &lt;Jason@zx2c4.com&gt;
Reviewed-by: Srikar Dronamraju &lt;srikar@linux.ibm.com&gt;
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191223133147.129983-1-Jason@zx2c4.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Recently, the spinlock implementation grew a static key optimization,
but the jump_label.h header include was left out, leading to build
errors:

  linux/arch/powerpc/include/asm/spinlock.h:44:7: error: implicit declaration of function ‘static_branch_unlikely’
   44 |  if (!static_branch_unlikely(&amp;shared_processor))

This commit adds the missing header.

mpe: The build break is only seen with CONFIG_JUMP_LABEL=n.

Fixes: 656c21d6af5d ("powerpc/shared: Use static key to detect shared processor")
Signed-off-by: Jason A. Donenfeld &lt;Jason@zx2c4.com&gt;
Reviewed-by: Srikar Dronamraju &lt;srikar@linux.ibm.com&gt;
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191223133147.129983-1-Jason@zx2c4.com
</pre>
</div>
</content>
</entry>
<entry>
<title>powerpc: Fix __clear_user() with KUAP enabled</title>
<updated>2019-12-16T12:19:44+00:00</updated>
<author>
<name>Andrew Donnellan</name>
<email>ajd@linux.ibm.com</email>
</author>
<published>2019-12-09T13:22:21+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=61e3acd8c693a14fc69b824cb5b08d02cb90a6e7'/>
<id>61e3acd8c693a14fc69b824cb5b08d02cb90a6e7</id>
<content type='text'>
The KUAP implementation adds calls in clear_user() to enable and
disable access to userspace memory. However, it doesn't add these to
__clear_user(), which is used in the ptrace regset code.

As there's only one direct user of __clear_user() (the regset code),
and the time taken to set the AMR for KUAP purposes is going to
dominate the cost of a quick access_ok(), there's not much point
having a separate path.

Rename __clear_user() to __arch_clear_user(), and make __clear_user()
just call clear_user().

Reported-by: syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com
Reported-by: Daniel Axtens &lt;dja@axtens.net&gt;
Suggested-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection")
Signed-off-by: Andrew Donnellan &lt;ajd@linux.ibm.com&gt;
[mpe: Use __arch_clear_user() for the asm version like arm64 &amp; nds32]
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@linux.ibm.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The KUAP implementation adds calls in clear_user() to enable and
disable access to userspace memory. However, it doesn't add these to
__clear_user(), which is used in the ptrace regset code.

As there's only one direct user of __clear_user() (the regset code),
and the time taken to set the AMR for KUAP purposes is going to
dominate the cost of a quick access_ok(), there's not much point
having a separate path.

Rename __clear_user() to __arch_clear_user(), and make __clear_user()
just call clear_user().

Reported-by: syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com
Reported-by: Daniel Axtens &lt;dja@axtens.net&gt;
Suggested-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection")
Signed-off-by: Andrew Donnellan &lt;ajd@linux.ibm.com&gt;
[mpe: Use __arch_clear_user() for the asm version like arm64 &amp; nds32]
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@linux.ibm.com
</pre>
</div>
</content>
</entry>
<entry>
<title>powerpc/shared: Use static key to detect shared processor</title>
<updated>2019-12-13T10:07:45+00:00</updated>
<author>
<name>Srikar Dronamraju</name>
<email>srikar@linux.vnet.ibm.com</email>
</author>
<published>2019-12-05T08:32:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=656c21d6af5d9279dd7b51ca7a4a71008127044b'/>
<id>656c21d6af5d9279dd7b51ca7a4a71008127044b</id>
<content type='text'>
With the static key shared processor available, is_shared_processor()
can return without having to query the lppaca structure.

Signed-off-by: Srikar Dronamraju &lt;srikar@linux.vnet.ibm.com&gt;
Acked-by: Phil Auld &lt;pauld@redhat.com&gt;
Acked-by: Waiman Long &lt;longman@redhat.com&gt;
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191213035036.6913-2-mpe@ellerman.id.au
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
With the static key shared processor available, is_shared_processor()
can return without having to query the lppaca structure.

Signed-off-by: Srikar Dronamraju &lt;srikar@linux.vnet.ibm.com&gt;
Acked-by: Phil Auld &lt;pauld@redhat.com&gt;
Acked-by: Waiman Long &lt;longman@redhat.com&gt;
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191213035036.6913-2-mpe@ellerman.id.au
</pre>
</div>
</content>
</entry>
<entry>
<title>powerpc/vcpu: Assume dedicated processors as non-preempt</title>
<updated>2019-12-13T10:06:57+00:00</updated>
<author>
<name>Srikar Dronamraju</name>
<email>srikar@linux.vnet.ibm.com</email>
</author>
<published>2019-12-05T08:32:17+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=14c73bd344da60abaf7da3ea2e7733ddda35bbac'/>
<id>14c73bd344da60abaf7da3ea2e7733ddda35bbac</id>
<content type='text'>
With commit 247f2f6f3c70 ("sched/core: Don't schedule threads on
pre-empted vCPUs"), the scheduler avoids preempted vCPUs to schedule
tasks on wakeup. This leads to wrong choice of CPU, which in-turn
leads to larger wakeup latencies. Eventually, it leads to performance
regression in latency sensitive benchmarks like soltp, schbench etc.

On Powerpc, vcpu_is_preempted() only looks at yield_count. If the
yield_count is odd, the vCPU is assumed to be preempted. However
yield_count is increased whenever the LPAR enters CEDE state (idle).
So any CPU that has entered CEDE state is assumed to be preempted.

Even if vCPU of dedicated LPAR is preempted/donated, it should have
right of first-use since they are supposed to own the vCPU.

On a Power9 System with 32 cores:
  # lscpu
  Architecture:        ppc64le
  Byte Order:          Little Endian
  CPU(s):              128
  On-line CPU(s) list: 0-127
  Thread(s) per core:  8
  Core(s) per socket:  1
  Socket(s):           16
  NUMA node(s):        2
  Model:               2.2 (pvr 004e 0202)
  Model name:          POWER9 (architected), altivec supported
  Hypervisor vendor:   pHyp
  Virtualization type: para
  L1d cache:           32K
  L1i cache:           32K
  L2 cache:            512K
  L3 cache:            10240K
  NUMA node0 CPU(s):   0-63
  NUMA node1 CPU(s):   64-127

  # perf stat -a -r 5 ./schbench
  v5.4                               v5.4 + patch
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 45
        75.0000th: 62                      75.0th: 63
        90.0000th: 71                      90.0th: 74
        95.0000th: 77                      95.0th: 78
        *99.0000th: 91                     *99.0th: 82
        99.5000th: 707                     99.5th: 83
        99.9000th: 6920                    99.9th: 86
        min=0, max=10048                   min=0, max=96
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 46
        75.0000th: 61                      75.0th: 64
        90.0000th: 72                      90.0th: 75
        95.0000th: 79                      95.0th: 79
        *99.0000th: 691                    *99.0th: 83
        99.5000th: 3972                    99.5th: 85
        99.9000th: 8368                    99.9th: 91
        min=0, max=16606                   min=0, max=117
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 46
        75.0000th: 61                      75.0th: 64
        90.0000th: 71                      90.0th: 75
        95.0000th: 77                      95.0th: 79
        *99.0000th: 106                    *99.0th: 83
        99.5000th: 2364                    99.5th: 84
        99.9000th: 7480                    99.9th: 90
        min=0, max=10001                   min=0, max=95
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 47
        75.0000th: 62                      75.0th: 65
        90.0000th: 72                      90.0th: 75
        95.0000th: 78                      95.0th: 79
        *99.0000th: 93                     *99.0th: 84
        99.5000th: 108                     99.5th: 85
        99.9000th: 6792                    99.9th: 90
        min=0, max=17681                   min=0, max=117
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 46                      50.0th: 45
        75.0000th: 62                      75.0th: 64
        90.0000th: 73                      90.0th: 75
        95.0000th: 79                      95.0th: 79
        *99.0000th: 113                    *99.0th: 82
        99.5000th: 2724                    99.5th: 83
        99.9000th: 6184                    99.9th: 93
        min=0, max=9887                    min=0, max=111

   Performance counter stats for 'system wide' (5 runs):

  context-switches    43,373  ( +-  0.40% )   44,597 ( +-  0.55% )
  cpu-migrations       1,211  ( +-  5.04% )      220 ( +-  6.23% )
  page-faults         15,983  ( +-  5.21% )   15,360 ( +-  3.38% )

Waiman Long suggested using static_keys.

Fixes: 247f2f6f3c70 ("sched/core: Don't schedule threads on pre-empted vCPUs")
Cc: stable@vger.kernel.org # v4.18+
Reported-by: Parth Shah &lt;parth@linux.ibm.com&gt;
Reported-by: Ihor Pasichnyk &lt;Ihor.Pasichnyk@ibm.com&gt;
Tested-by: Juri Lelli &lt;juri.lelli@redhat.com&gt;
Acked-by: Waiman Long &lt;longman@redhat.com&gt;
Reviewed-by: Gautham R. Shenoy &lt;ego@linux.vnet.ibm.com&gt;
Signed-off-by: Srikar Dronamraju &lt;srikar@linux.vnet.ibm.com&gt;
Acked-by: Phil Auld &lt;pauld@redhat.com&gt;
Reviewed-by: Vaidyanathan Srinivasan &lt;svaidy@linux.ibm.com&gt;
Tested-by: Parth Shah &lt;parth@linux.ibm.com&gt;
[mpe: Move the key and setting of the key to pseries/setup.c]
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191213035036.6913-1-mpe@ellerman.id.au
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
With commit 247f2f6f3c70 ("sched/core: Don't schedule threads on
pre-empted vCPUs"), the scheduler avoids preempted vCPUs to schedule
tasks on wakeup. This leads to wrong choice of CPU, which in-turn
leads to larger wakeup latencies. Eventually, it leads to performance
regression in latency sensitive benchmarks like soltp, schbench etc.

On Powerpc, vcpu_is_preempted() only looks at yield_count. If the
yield_count is odd, the vCPU is assumed to be preempted. However
yield_count is increased whenever the LPAR enters CEDE state (idle).
So any CPU that has entered CEDE state is assumed to be preempted.

Even if vCPU of dedicated LPAR is preempted/donated, it should have
right of first-use since they are supposed to own the vCPU.

On a Power9 System with 32 cores:
  # lscpu
  Architecture:        ppc64le
  Byte Order:          Little Endian
  CPU(s):              128
  On-line CPU(s) list: 0-127
  Thread(s) per core:  8
  Core(s) per socket:  1
  Socket(s):           16
  NUMA node(s):        2
  Model:               2.2 (pvr 004e 0202)
  Model name:          POWER9 (architected), altivec supported
  Hypervisor vendor:   pHyp
  Virtualization type: para
  L1d cache:           32K
  L1i cache:           32K
  L2 cache:            512K
  L3 cache:            10240K
  NUMA node0 CPU(s):   0-63
  NUMA node1 CPU(s):   64-127

  # perf stat -a -r 5 ./schbench
  v5.4                               v5.4 + patch
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 45
        75.0000th: 62                      75.0th: 63
        90.0000th: 71                      90.0th: 74
        95.0000th: 77                      95.0th: 78
        *99.0000th: 91                     *99.0th: 82
        99.5000th: 707                     99.5th: 83
        99.9000th: 6920                    99.9th: 86
        min=0, max=10048                   min=0, max=96
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 46
        75.0000th: 61                      75.0th: 64
        90.0000th: 72                      90.0th: 75
        95.0000th: 79                      95.0th: 79
        *99.0000th: 691                    *99.0th: 83
        99.5000th: 3972                    99.5th: 85
        99.9000th: 8368                    99.9th: 91
        min=0, max=16606                   min=0, max=117
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 46
        75.0000th: 61                      75.0th: 64
        90.0000th: 71                      90.0th: 75
        95.0000th: 77                      95.0th: 79
        *99.0000th: 106                    *99.0th: 83
        99.5000th: 2364                    99.5th: 84
        99.9000th: 7480                    99.9th: 90
        min=0, max=10001                   min=0, max=95
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 45                      50.0th: 47
        75.0000th: 62                      75.0th: 65
        90.0000th: 72                      90.0th: 75
        95.0000th: 78                      95.0th: 79
        *99.0000th: 93                     *99.0th: 84
        99.5000th: 108                     99.5th: 85
        99.9000th: 6792                    99.9th: 90
        min=0, max=17681                   min=0, max=117
  Latency percentiles (usec)         Latency percentiles (usec)
        50.0000th: 46                      50.0th: 45
        75.0000th: 62                      75.0th: 64
        90.0000th: 73                      90.0th: 75
        95.0000th: 79                      95.0th: 79
        *99.0000th: 113                    *99.0th: 82
        99.5000th: 2724                    99.5th: 83
        99.9000th: 6184                    99.9th: 93
        min=0, max=9887                    min=0, max=111

   Performance counter stats for 'system wide' (5 runs):

  context-switches    43,373  ( +-  0.40% )   44,597 ( +-  0.55% )
  cpu-migrations       1,211  ( +-  5.04% )      220 ( +-  6.23% )
  page-faults         15,983  ( +-  5.21% )   15,360 ( +-  3.38% )

Waiman Long suggested using static_keys.

Fixes: 247f2f6f3c70 ("sched/core: Don't schedule threads on pre-empted vCPUs")
Cc: stable@vger.kernel.org # v4.18+
Reported-by: Parth Shah &lt;parth@linux.ibm.com&gt;
Reported-by: Ihor Pasichnyk &lt;Ihor.Pasichnyk@ibm.com&gt;
Tested-by: Juri Lelli &lt;juri.lelli@redhat.com&gt;
Acked-by: Waiman Long &lt;longman@redhat.com&gt;
Reviewed-by: Gautham R. Shenoy &lt;ego@linux.vnet.ibm.com&gt;
Signed-off-by: Srikar Dronamraju &lt;srikar@linux.vnet.ibm.com&gt;
Acked-by: Phil Auld &lt;pauld@redhat.com&gt;
Reviewed-by: Vaidyanathan Srinivasan &lt;svaidy@linux.ibm.com&gt;
Tested-by: Parth Shah &lt;parth@linux.ibm.com&gt;
[mpe: Move the key and setting of the key to pseries/setup.c]
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
Link: https://lore.kernel.org/r/20191213035036.6913-1-mpe@ellerman.id.au
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'powerpc-5.5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux</title>
<updated>2019-12-06T21:36:31+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-12-06T21:36:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=43a2898631a8beee66c1d64c1e860f43d96b2e91'/>
<id>43a2898631a8beee66c1d64c1e860f43d96b2e91</id>
<content type='text'>
Pull more powerpc updates from Michael Ellerman:
 "A few commits splitting the KASAN instrumented bitops header in three,
  to match the split of the asm-generic bitops headers.

  This is needed on powerpc because we use the generic bitops for the
  non-atomic case only, whereas the existing KASAN instrumented bitops
  assume all the underlying operations are provided by the arch as
  arch_foo() versions.

  Thanks to: Daniel Axtens &amp; Christophe Leroy"

* tag 'powerpc-5.5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  docs/core-api: Remove possibly confusing sub-headings from Bit Operations
  powerpc: support KASAN instrumentation of bitops
  kasan: support instrumented bitops combined with generic bitops
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull more powerpc updates from Michael Ellerman:
 "A few commits splitting the KASAN instrumented bitops header in three,
  to match the split of the asm-generic bitops headers.

  This is needed on powerpc because we use the generic bitops for the
  non-atomic case only, whereas the existing KASAN instrumented bitops
  assume all the underlying operations are provided by the arch as
  arch_foo() versions.

  Thanks to: Daniel Axtens &amp; Christophe Leroy"

* tag 'powerpc-5.5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  docs/core-api: Remove possibly confusing sub-headings from Bit Operations
  powerpc: support KASAN instrumentation of bitops
  kasan: support instrumented bitops combined with generic bitops
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'powerpc-5.5-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux</title>
<updated>2019-12-06T21:34:31+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-12-06T21:34:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=f89d416a8676fe36de8be0f7c2e1ac6cd51410a8'/>
<id>f89d416a8676fe36de8be0f7c2e1ac6cd51410a8</id>
<content type='text'>
Pull powerpc fixes from Michael Ellerman:
 "One fix for a regression introduced by our recent rework of cache
  flushing on memory hotunplug.

  Like several other arches, our VDSO clock_getres() needed a fix to
  match the semantics of posix_get_hrtimer_res().

  A fix for a boot crash on Power9 LPARs using PCI LSI interrupts.

  A commit disabling use of the trace_imc PMU (not the core PMU) on
  Power9 systems, because it can lead to checkstops, until a workaround
  is developed.

  A handful of other minor fixes.

  Thanks to: Aneesh Kumar K.V, Anju T Sudhakar, Ard Biesheuvel,
  Christophe Leroy, Cédric Le Goater, Madhavan Srinivasan, Vincenzo
  Frascino"

* tag 'powerpc-5.5-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/perf: Disable trace_imc pmu
  powerpc/powernv: Avoid re-registration of imc debugfs directory
  powerpc/pmem: Convert to EXPORT_SYMBOL_GPL
  powerpc/archrandom: fix arch_get_random_seed_int()
  powerpc: Fix vDSO clock_getres()
  powerpc/pmem: Fix kernel crash due to wrong range value usage in flush_dcache_range
  powerpc/xive: Skip ioremap() of ESB pages for LSI interrupts
  powerpc/kasan: Fix boot failure with RELOCATABLE &amp;&amp; FSL_BOOKE
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull powerpc fixes from Michael Ellerman:
 "One fix for a regression introduced by our recent rework of cache
  flushing on memory hotunplug.

  Like several other arches, our VDSO clock_getres() needed a fix to
  match the semantics of posix_get_hrtimer_res().

  A fix for a boot crash on Power9 LPARs using PCI LSI interrupts.

  A commit disabling use of the trace_imc PMU (not the core PMU) on
  Power9 systems, because it can lead to checkstops, until a workaround
  is developed.

  A handful of other minor fixes.

  Thanks to: Aneesh Kumar K.V, Anju T Sudhakar, Ard Biesheuvel,
  Christophe Leroy, Cédric Le Goater, Madhavan Srinivasan, Vincenzo
  Frascino"

* tag 'powerpc-5.5-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/perf: Disable trace_imc pmu
  powerpc/powernv: Avoid re-registration of imc debugfs directory
  powerpc/pmem: Convert to EXPORT_SYMBOL_GPL
  powerpc/archrandom: fix arch_get_random_seed_int()
  powerpc: Fix vDSO clock_getres()
  powerpc/pmem: Fix kernel crash due to wrong range value usage in flush_dcache_range
  powerpc/xive: Skip ioremap() of ESB pages for LSI interrupts
  powerpc/kasan: Fix boot failure with RELOCATABLE &amp;&amp; FSL_BOOKE
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'akpm' (patches from Andrew)</title>
<updated>2019-12-05T17:46:26+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-12-05T17:46:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5ecc9d15f73b82c748526350d5602c94fdd65cac'/>
<id>5ecc9d15f73b82c748526350d5602c94fdd65cac</id>
<content type='text'>
Merge more updates from Andrew Morton:
 "Most of the rest of MM and various other things. Some Kconfig rework
  still awaits merges of dependent trees from linux-next.

  Subsystems affected by this patch series: mm/hotfixes, mm/memcg,
  mm/vmstat, mm/thp, procfs, sysctl, misc, notifiers, core-kernel,
  bitops, lib, checkpatch, epoll, binfmt, init, rapidio, uaccess, kcov,
  ubsan, ipc, bitmap, mm/pagemap"

* akpm: (86 commits)
  mm: remove __ARCH_HAS_4LEVEL_HACK and include/asm-generic/4level-fixup.h
  um: add support for folded p4d page tables
  um: remove unused pxx_offset_proc() and addr_pte() functions
  sparc32: use pgtable-nopud instead of 4level-fixup
  parisc/hugetlb: use pgtable-nopXd instead of 4level-fixup
  parisc: use pgtable-nopXd instead of 4level-fixup
  nds32: use pgtable-nopmd instead of 4level-fixup
  microblaze: use pgtable-nopmd instead of 4level-fixup
  m68k: mm: use pgtable-nopXd instead of 4level-fixup
  m68k: nommu: use pgtable-nopud instead of 4level-fixup
  c6x: use pgtable-nopud instead of 4level-fixup
  arm: nommu: use pgtable-nopud instead of 4level-fixup
  alpha: use pgtable-nopud instead of 4level-fixup
  gpio: pca953x: tighten up indentation
  gpio: pca953x: convert to use bitmap API
  gpio: pca953x: use input from regs structure in pca953x_irq_pending()
  gpio: pca953x: remove redundant variable and check in IRQ handler
  lib/bitmap: introduce bitmap_replace() helper
  lib/test_bitmap: fix comment about this file
  lib/test_bitmap: move exp1 and exp2 upper for others to use
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Merge more updates from Andrew Morton:
 "Most of the rest of MM and various other things. Some Kconfig rework
  still awaits merges of dependent trees from linux-next.

  Subsystems affected by this patch series: mm/hotfixes, mm/memcg,
  mm/vmstat, mm/thp, procfs, sysctl, misc, notifiers, core-kernel,
  bitops, lib, checkpatch, epoll, binfmt, init, rapidio, uaccess, kcov,
  ubsan, ipc, bitmap, mm/pagemap"

* akpm: (86 commits)
  mm: remove __ARCH_HAS_4LEVEL_HACK and include/asm-generic/4level-fixup.h
  um: add support for folded p4d page tables
  um: remove unused pxx_offset_proc() and addr_pte() functions
  sparc32: use pgtable-nopud instead of 4level-fixup
  parisc/hugetlb: use pgtable-nopXd instead of 4level-fixup
  parisc: use pgtable-nopXd instead of 4level-fixup
  nds32: use pgtable-nopmd instead of 4level-fixup
  microblaze: use pgtable-nopmd instead of 4level-fixup
  m68k: mm: use pgtable-nopXd instead of 4level-fixup
  m68k: nommu: use pgtable-nopud instead of 4level-fixup
  c6x: use pgtable-nopud instead of 4level-fixup
  arm: nommu: use pgtable-nopud instead of 4level-fixup
  alpha: use pgtable-nopud instead of 4level-fixup
  gpio: pca953x: tighten up indentation
  gpio: pca953x: convert to use bitmap API
  gpio: pca953x: use input from regs structure in pca953x_irq_pending()
  gpio: pca953x: remove redundant variable and check in IRQ handler
  lib/bitmap: introduce bitmap_replace() helper
  lib/test_bitmap: fix comment about this file
  lib/test_bitmap: move exp1 and exp2 upper for others to use
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>arch: sembuf.h: make uapi asm/sembuf.h self-contained</title>
<updated>2019-12-05T03:44:14+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>yamada.masahiro@socionext.com</email>
</author>
<published>2019-12-05T00:53:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=0fb9dc28679a627f84974165c8011e0630529ece'/>
<id>0fb9dc28679a627f84974165c8011e0630529ece</id>
<content type='text'>
Userspace cannot compile &lt;asm/sembuf.h&gt; due to some missing type
definitions.  For example, building it for x86 fails as follows:

    CC      usr/include/asm/sembuf.h.s
  In file included from &lt;command-line&gt;:32:0:
  usr/include/asm/sembuf.h:17:20: error: field `sem_perm' has incomplete type
    struct ipc64_perm sem_perm; /* permissions .. see ipc.h */
                      ^~~~~~~~
  usr/include/asm/sembuf.h:24:2: error: unknown type name `__kernel_time_t'
    __kernel_time_t sem_otime; /* last semop time */
    ^~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:25:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused1;
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:26:2: error: unknown type name `__kernel_time_t'
    __kernel_time_t sem_ctime; /* last change time */
    ^~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:27:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused2;
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:29:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t sem_nsems; /* no. of semaphores in array */
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:30:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused3;
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:31:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused4;
    ^~~~~~~~~~~~~~~~

It is just a matter of missing include directive.

Include &lt;asm/ipcbuf.h&gt; to make it self-contained, and add it to
the compile-test coverage.

Link: http://lkml.kernel.org/r/20191030063855.9989-3-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Userspace cannot compile &lt;asm/sembuf.h&gt; due to some missing type
definitions.  For example, building it for x86 fails as follows:

    CC      usr/include/asm/sembuf.h.s
  In file included from &lt;command-line&gt;:32:0:
  usr/include/asm/sembuf.h:17:20: error: field `sem_perm' has incomplete type
    struct ipc64_perm sem_perm; /* permissions .. see ipc.h */
                      ^~~~~~~~
  usr/include/asm/sembuf.h:24:2: error: unknown type name `__kernel_time_t'
    __kernel_time_t sem_otime; /* last semop time */
    ^~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:25:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused1;
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:26:2: error: unknown type name `__kernel_time_t'
    __kernel_time_t sem_ctime; /* last change time */
    ^~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:27:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused2;
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:29:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t sem_nsems; /* no. of semaphores in array */
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:30:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused3;
    ^~~~~~~~~~~~~~~~
  usr/include/asm/sembuf.h:31:2: error: unknown type name `__kernel_ulong_t'
    __kernel_ulong_t __unused4;
    ^~~~~~~~~~~~~~~~

It is just a matter of missing include directive.

Include &lt;asm/ipcbuf.h&gt; to make it self-contained, and add it to
the compile-test coverage.

Link: http://lkml.kernel.org/r/20191030063855.9989-3-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
