linux-stable.git/arch/x86/include, branch linux-5.14.y

Revert "sched: Add wrapper for get_wchan() to keep task blocked"

2021-11-18T13:01:34+00:00

This reverts commit e9ede14c116f1a6246eee89d320d60a90a86b5d5 which is
commit 42a20f86dc19f9282d974df0ba4d226c865ab9dd upstream.

It has been reported to be causing problems, and is being reworked
upstream and has been dropped from the current 5.15.y stable queue until
it gets resolved.

Reported-by: Chris Rankin 
Reported-by: Thorsten Leemhuis 
Link: https://lore.kernel.org/r/ed000478-2a60-0066-c337-a04bffc112b1@leemhuis.info
Cc: Stephen Rothwell 
Cc: Peter Zijlstra (Intel) 
Cc: Kees Cook 
Cc: Geert Uytterhoeven 
Cc: Russell King (Oracle) 
Cc: Mark Rutland 
Cc: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

x86/sev: Make the #VC exception stacks part of the default stacks storage

2021-11-17T10:04:52+00:00

commit 541ac97186d9ea88491961a46284de3603c914fd upstream.

The size of the exception stacks was increased by the commit in Fixes,
resulting in stack sizes greater than a page in size. The #VC exception
handling was only mapping the first (bottom) page, resulting in an
SEV-ES guest failing to boot.

Make the #VC exception stacks part of the default exception stacks
storage and allocate them with a CONFIG_AMD_MEM_ENCRYPT=y .config. Map
them only when a SEV-ES guest has been detected.

Rip out the custom VC stacks mapping and storage code.

 [ bp: Steal and adapt Tom's commit message. ]

Fixes: 7fae4c24a2b8 ("x86: Increase exception stack sizes")
Signed-off-by: Borislav Petkov 
Tested-by: Tom Lendacky 
Tested-by: Brijesh Singh 
Link: https://lkml.kernel.org/r/YVt1IMjIs7pIZTRR@zn.tnic
Signed-off-by: Greg Kroah-Hartman

x86/sev: Add an x86 version of cc_platform_has()

2021-11-17T10:04:52+00:00

commit aa5a461171f98fde0df78c4f6b5018a1e967cf81 upstream.

Introduce an x86 version of the cc_platform_has() function. This will be
used to replace vendor specific calls like sme_active(), sev_active(),
etc.

Signed-off-by: Tom Lendacky 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210928191009.32551-4-bp@alien8.de
Signed-off-by: Greg Kroah-Hartman

sched: Add wrapper for get_wchan() to keep task blocked

2021-11-17T10:04:16+00:00

[ Upstream commit 42a20f86dc19f9282d974df0ba4d226c865ab9dd ]

Having a stable wchan means the process must be blocked and for it to
stay that way while performing stack unwinding.

Suggested-by: Peter Zijlstra 
Signed-off-by: Kees Cook 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Geert Uytterhoeven 
Acked-by: Russell King (Oracle)  [arm]
Tested-by: Mark Rutland  [arm64]
Link: https://lkml.kernel.org/r/20211008111626.332092234@infradead.org
Signed-off-by: Sasha Levin

x86: Increase exception stack sizes

2021-11-17T10:03:45+00:00

[ Upstream commit 7fae4c24a2b84a66c7be399727aca11e7a888462 ]

It turns out that a single page of stack is trivial to overflow with
all the tracing gunk enabled. Raise the exception stacks to 2 pages,
which is still half the interrupt stacks, which are at 4 pages.

Reported-by: Michael Wang 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/YUIO9Ye98S5Eb68w@hirez.programming.kicks-ass.net
Signed-off-by: Sasha Levin

x86/mm/64: Improve stack overflow warnings

2021-11-17T10:03:45+00:00

[ Upstream commit 44b979fa302cab91bdd2cc982823e5c13202cd4e ]

Current code has an explicit check for hitting the task stack guard;
but overflowing any of the other stacks will get you a non-descript
general #DF warning.

Improve matters by using get_stack_info_noinstr() to detetrmine if and
which stack guard page got hit, enabling a better stack warning.

In specific, Michael Wang reported what turned out to be an NMI
exception stack overflow, which is now clearly reported as such:

  [] BUG: NMI stack guard page was hit at 0000000085fd977b (stack is 000000003a55b09e..00000000d8cce1a5)

Reported-by: Michael Wang 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Michael Wang 
Link: https://lkml.kernel.org/r/YUTE/NuqnaWbST8n@hirez.programming.kicks-ass.net
Signed-off-by: Sasha Levin

KVM: x86: Fix recording of guest steal time / preempted status

2021-11-17T10:03:38+00:00

commit 7e2175ebd695f17860c5bd4ad7616cce12ed4591 upstream.

In commit b043138246a4 ("x86/KVM: Make sure KVM_VCPU_FLUSH_TLB flag is
not missed") we switched to using a gfn_to_pfn_cache for accessing the
guest steal time structure in order to allow for an atomic xchg of the
preempted field. This has a couple of problems.

Firstly, kvm_map_gfn() doesn't work at all for IOMEM pages when the
atomic flag is set, which it is in kvm_steal_time_set_preempted(). So a
guest vCPU using an IOMEM page for its steal time would never have its
preempted field set.

Secondly, the gfn_to_pfn_cache is not invalidated in all cases where it
should have been. There are two stages to the GFN->PFN conversion;
first the GFN is converted to a userspace HVA, and then that HVA is
looked up in the process page tables to find the underlying host PFN.
Correct invalidation of the latter would require being hooked up to the
MMU notifiers, but that doesn't happen---so it just keeps mapping and
unmapping the *wrong* PFN after the userspace page tables change.

In the !IOMEM case at least the stale page *is* pinned all the time it's
cached, so it won't be freed and reused by anyone else while still
receiving the steal time updates. The map/unmap dance only takes care
of the KVM administrivia such as marking the page dirty.

Until the gfn_to_pfn cache handles the remapping automatically by
integrating with the MMU notifiers, we might as well not get a
kernel mapping of it, and use the perfectly serviceable userspace HVA
that we already have.  We just need to implement the atomic xchg on
the userspace address with appropriate exception handling, which is
fairly trivial.

Cc: stable@vger.kernel.org
Fixes: b043138246a4 ("x86/KVM: Make sure KVM_VCPU_FLUSH_TLB flag is not missed")
Signed-off-by: David Woodhouse 
Message-Id: <3645b9b889dac6438394194bb5586a46b68d581f.camel@infradead.org>
[I didn't entirely agree with David's assessment of the
 usefulness of the gfn_to_pfn cache, and integrated the outcome
 of the discussion in the above commit message. - Paolo]
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

x86/iopl: Fake iopl(3) CLI/STI usage

2021-11-17T10:03:27+00:00

commit b968e84b509da593c50dc3db679e1d33de701f78 upstream.

Since commit c8137ace5638 ("x86/iopl: Restrict iopl() permission
scope") it's possible to emulate iopl(3) using ioperm(), except for
the CLI/STI usage.

Userspace CLI/STI usage is very dubious (read broken), since any
exception taken during that window can lead to rescheduling anyway (or
worse). The IOPL(2) manpage even states that usage of CLI/STI is highly
discouraged and might even crash the system.

Of course, that won't stop people and HP has the dubious honour of
being the first vendor to be found using this in their hp-health
package.

In order to enable this 'software' to still 'work', have the #GP treat
the CLI/STI instructions as NOPs when iopl(3). Warn the user that
their program is doing dubious things.

Fixes: a24ca9976843 ("x86/iopl: Remove legacy IOPL option")
Reported-by: Ondrej Zary 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Cc: stable@kernel.org # v5.5+
Link: https://lkml.kernel.org/r/20210918090641.GD5106@worktop.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman

KVM: x86: switch pvclock_gtod_sync_lock to a raw spinlock

2021-11-02T18:51:02+00:00

commit 8228c77d8b56e3f735baf71fefb1b548c23691a7 upstream.

On the preemption path when updating a Xen guest's runstate times, this
lock is taken inside the scheduler rq->lock, which is a raw spinlock.
This was shown in a lockdep warning:

[   89.138354] =============================
[   89.138356] [ BUG: Invalid wait context ]
[   89.138358] 5.15.0-rc5+ #834 Tainted: G S        I E
[   89.138360] -----------------------------
[   89.138361] xen_shinfo_test/2575 is trying to lock:
[   89.138363] ffffa34a0364efd8 (&kvm->arch.pvclock_gtod_sync_lock){....}-{3:3}, at: get_kvmclock_ns+0x1f/0x130 [kvm]
[   89.138442] other info that might help us debug this:
[   89.138444] context-{5:5}
[   89.138445] 4 locks held by xen_shinfo_test/2575:
[   89.138447]  #0: ffff972bdc3b8108 (&vcpu->mutex){+.+.}-{4:4}, at: kvm_vcpu_ioctl+0x77/0x6f0 [kvm]
[   89.138483]  #1: ffffa34a03662e90 (&kvm->srcu){....}-{0:0}, at: kvm_arch_vcpu_ioctl_run+0xdc/0x8b0 [kvm]
[   89.138526]  #2: ffff97331fdbac98 (&rq->__lock){-.-.}-{2:2}, at: __schedule+0xff/0xbd0
[   89.138534]  #3: ffffa34a03662e90 (&kvm->srcu){....}-{0:0}, at: kvm_arch_vcpu_put+0x26/0x170 [kvm]
...
[   89.138695]  get_kvmclock_ns+0x1f/0x130 [kvm]
[   89.138734]  kvm_xen_update_runstate+0x14/0x90 [kvm]
[   89.138783]  kvm_xen_update_runstate_guest+0x15/0xd0 [kvm]
[   89.138830]  kvm_arch_vcpu_put+0xe6/0x170 [kvm]
[   89.138870]  kvm_sched_out+0x2f/0x40 [kvm]
[   89.138900]  __schedule+0x5de/0xbd0

Cc: stable@vger.kernel.org
Reported-by: syzbot+b282b65c2c68492df769@syzkaller.appspotmail.com
Fixes: 30b5c851af79 ("KVM: x86/xen: Add support for vCPU runstate information")
Signed-off-by: David Woodhouse 
Message-Id: <1b02a06421c17993df337493a68ba923f3bd5c0f.camel@infradead.org>
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

KVM: SEV-ES: go over the sev_pio_data buffer in multiple passes if needed

2021-10-27T07:59:47+00:00

commit 95e16b4792b0429f1933872f743410f00e590c55 upstream.

The PIO scratch buffer is larger than a single page, and therefore
it is not possible to copy it in a single step to vcpu->arch/pio_data.
Bound each call to emulator_pio_in/out to a single page; keep
track of how many I/O operations are left in vcpu->arch.sev_pio_count,
so that the operation can be restarted in the complete_userspace_io
callback.

For OUT, this means that the previous kvm_sev_es_outs implementation
becomes an iterator of the loop, and we can consume the sev_pio_data
buffer before leaving to userspace.

For IN, instead, consuming the buffer and decreasing sev_pio_count
is always done in the complete_userspace_io callback, because that
is when the memcpy is done into sev_pio_data.

Cc: stable@vger.kernel.org
Fixes: 7ed9abfe8e9f ("KVM: SVM: Support string IO operations for an SEV-ES guest")
Reported-by: Felix Wilhelm 
Reviewed-by: Maxim Levitsky 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman