<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/arch/arc, branch v4.19.321</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>ARC: [plat-hsdk]: Remove misplaced interrupt-cells property</title>
<updated>2024-05-02T14:17:11+00:00</updated>
<author>
<name>Alexey Brodkin</name>
<email>Alexey.Brodkin@synopsys.com</email>
</author>
<published>2024-03-29T10:36:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=60874cc9e4d57c357266ad8b1b1b3b960be8af77'/>
<id>60874cc9e4d57c357266ad8b1b1b3b960be8af77</id>
<content type='text'>
[ Upstream commit 61231eb8113ce47991f35024f9c20810b37996bf ]

"gmac" node stands for just an ordinary Ethernet controller,
which is by no means a provider of interrupts, i.e. it doesn't serve
as an interrupt controller, thus "#interrupt-cells" property doesn't
belong to it and so we remove it.

Fixes:
------------&gt;8------------
  DTC     arch/arc/boot/dts/hsdk.dtb
arch/arc/boot/dts/hsdk.dts:207.23-235.5: Warning (interrupt_provider): /soc/ethernet@8000: '#interrupt-cells' found, but node is not an interrupt provider
arch/arc/boot/dts/hsdk.dtb: Warning (interrupt_map): Failed prerequisite 'interrupt_provider'
------------&gt;8------------

Reported-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Alexey Brodkin &lt;abrodkin@synopsys.com&gt;
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 61231eb8113ce47991f35024f9c20810b37996bf ]

"gmac" node stands for just an ordinary Ethernet controller,
which is by no means a provider of interrupts, i.e. it doesn't serve
as an interrupt controller, thus "#interrupt-cells" property doesn't
belong to it and so we remove it.

Fixes:
------------&gt;8------------
  DTC     arch/arc/boot/dts/hsdk.dtb
arch/arc/boot/dts/hsdk.dts:207.23-235.5: Warning (interrupt_provider): /soc/ethernet@8000: '#interrupt-cells' found, but node is not an interrupt provider
arch/arc/boot/dts/hsdk.dtb: Warning (interrupt_map): Failed prerequisite 'interrupt_provider'
------------&gt;8------------

Reported-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Alexey Brodkin &lt;abrodkin@synopsys.com&gt;
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARC: fix spare error</title>
<updated>2024-01-25T22:33:30+00:00</updated>
<author>
<name>Vineet Gupta</name>
<email>vgupta@kernel.org</email>
</author>
<published>2023-12-08T23:57:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=c536440b603111f5fcafa36050d2481f29f23e92'/>
<id>c536440b603111f5fcafa36050d2481f29f23e92</id>
<content type='text'>
[ Upstream commit aca02d933f63ba8bc84258bf35f9ffaf6b664336 ]

Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Closes: https://lore.kernel.org/oe-kbuild-all/202312082320.VDN5A9hb-lkp@intel.com/
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit aca02d933f63ba8bc84258bf35f9ffaf6b664336 ]

Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Closes: https://lore.kernel.org/oe-kbuild-all/202312082320.VDN5A9hb-lkp@intel.com/
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard</title>
<updated>2023-08-11T09:45:11+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>masahiroy@kernel.org</email>
</author>
<published>2023-06-11T15:50:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=f4f9e6f1386d483145a3f613b5bd5077b7085d1a'/>
<id>f4f9e6f1386d483145a3f613b5bd5077b7085d1a</id>
<content type='text'>
[ Upstream commit 92e2921eeafdfca9acd9b83f07d2b7ca099bac24 ]

ASM_NL is useful not only in *.S files but also in .c files for using
inline assembler in C code.

On ARC, however, ASM_NL is evaluated inconsistently. It is expanded to
a backquote (`) in *.S files, but a semicolon (;) in *.c files because
arch/arc/include/asm/linkage.h defines it inside #ifdef __ASSEMBLY__,
so the definition for C code falls back to the default value defined in
include/linux/linkage.h.

If ASM_NL is used in inline assembler in .c files, it will result in
wrong assembly code because a semicolon is not an instruction separator,
but the start of a comment for ARC.

Move ASM_NL (also __ALIGN and __ALIGN_STR) out of the #ifdef.

Fixes: 9df62f054406 ("arch: use ASM_NL instead of ';' for assembler new line character in the macro")
Fixes: 8d92e992a785 ("ARC: define __ALIGN_STR and __ALIGN symbols for ARC")
Signed-off-by: Masahiro Yamada &lt;masahiroy@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 92e2921eeafdfca9acd9b83f07d2b7ca099bac24 ]

ASM_NL is useful not only in *.S files but also in .c files for using
inline assembler in C code.

On ARC, however, ASM_NL is evaluated inconsistently. It is expanded to
a backquote (`) in *.S files, but a semicolon (;) in *.c files because
arch/arc/include/asm/linkage.h defines it inside #ifdef __ASSEMBLY__,
so the definition for C code falls back to the default value defined in
include/linux/linkage.h.

If ASM_NL is used in inline assembler in .c files, it will result in
wrong assembly code because a semicolon is not an instruction separator,
but the start of a comment for ARC.

Move ASM_NL (also __ALIGN and __ALIGN_STR) out of the #ifdef.

Fixes: 9df62f054406 ("arch: use ASM_NL instead of ';' for assembler new line character in the macro")
Fixes: 8d92e992a785 ("ARC: define __ALIGN_STR and __ALIGN symbols for ARC")
Signed-off-by: Masahiro Yamada &lt;masahiroy@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARCv2: entry: rewrite to enable use of double load/stores LDD/STD</title>
<updated>2023-08-11T09:45:11+00:00</updated>
<author>
<name>Vineet Gupta</name>
<email>vgupta@synopsys.com</email>
</author>
<published>2019-05-15T22:36:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=4ac3a2220d672f648ed10eda34ce884031ea1fa3'/>
<id>4ac3a2220d672f648ed10eda34ce884031ea1fa3</id>
<content type='text'>
[ Upstream commit a4880801a72ecc2dcdfa432f81a754f3e7438567 ]

 - the motivation was to be remove blatent copy-paste due to hasty support
   of CONFIG_ARC_IRQ_NO_AUTOSAVE support

 - but with refactoring we could use LDD/STD to greatly optimize the code

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit a4880801a72ecc2dcdfa432f81a754f3e7438567 ]

 - the motivation was to be remove blatent copy-paste due to hasty support
   of CONFIG_ARC_IRQ_NO_AUTOSAVE support

 - but with refactoring we could use LDD/STD to greatly optimize the code

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARCv2: entry: avoid a branch</title>
<updated>2023-08-11T09:45:11+00:00</updated>
<author>
<name>Vineet Gupta</name>
<email>vgupta@synopsys.com</email>
</author>
<published>2019-05-10T23:24:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=baea6f9bd6d3f8a65d2dbb010cc653f81f17c699'/>
<id>baea6f9bd6d3f8a65d2dbb010cc653f81f17c699</id>
<content type='text'>
[ Upstream commit ab854bfcd310b5872fe12eb8d3f2c30fe427f8f7 ]

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit ab854bfcd310b5872fe12eb8d3f2c30fe427f8f7 ]

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARCv2: entry: push out the Z flag unclobber from common EXCEPTION_PROLOGUE</title>
<updated>2023-08-11T09:45:10+00:00</updated>
<author>
<name>Vineet Gupta</name>
<email>vgupta@synopsys.com</email>
</author>
<published>2019-04-10T02:16:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=648d4e3957d0c1f57d9ef936b03fc0dcf56f2c99'/>
<id>648d4e3957d0c1f57d9ef936b03fc0dcf56f2c99</id>
<content type='text'>
[ Upstream commit 23c0cbd0c75c3b564850294427fd2be2bc2a015b ]

Upon a taken interrupt/exception from User mode, HS hardware auto sets Z flag.
This helps shave a few instructions from EXCEPTION_PROLOGUE by eliding
re-reading ERSTATUS and some bit fiddling.

However TLB Miss Exception handler can clobber the CPU flags and still end
up in EXCEPTION_PROLOGUE in the slow path handling TLB handling case:

   EV_TLBMissD
     do_slow_path_pf
       EV_TLBProtV (aliased to call_do_page_fault)
          EXCEPTION_PROLOGUE

As a result, EXCEPTION_PROLOGUE need to "unclobber" the Z flag which this
patch changes. It is now pushed out to TLB Miss Exception handler.
The reasons beings:

 - The flag restoration is only needed for slowpath TLB Miss Exception
   handling, but currently being in EXCEPTION_PROLOGUE penalizes all
   exceptions such as ProtV and syscall Trap, where Z flag is already
   as expected.

 - Pushing unclobber out to where it was clobbered is much cleaner and
   also serves to document the fact.

 - Makes EXCEPTION_PROLGUE similar to INTERRUPT_PROLOGUE so easier to
   refactor the common parts which is what this series aims to do

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 23c0cbd0c75c3b564850294427fd2be2bc2a015b ]

Upon a taken interrupt/exception from User mode, HS hardware auto sets Z flag.
This helps shave a few instructions from EXCEPTION_PROLOGUE by eliding
re-reading ERSTATUS and some bit fiddling.

However TLB Miss Exception handler can clobber the CPU flags and still end
up in EXCEPTION_PROLOGUE in the slow path handling TLB handling case:

   EV_TLBMissD
     do_slow_path_pf
       EV_TLBProtV (aliased to call_do_page_fault)
          EXCEPTION_PROLOGUE

As a result, EXCEPTION_PROLOGUE need to "unclobber" the Z flag which this
patch changes. It is now pushed out to TLB Miss Exception handler.
The reasons beings:

 - The flag restoration is only needed for slowpath TLB Miss Exception
   handling, but currently being in EXCEPTION_PROLOGUE penalizes all
   exceptions such as ProtV and syscall Trap, where Z flag is already
   as expected.

 - Pushing unclobber out to where it was clobbered is much cleaner and
   also serves to document the fact.

 - Makes EXCEPTION_PROLGUE similar to INTERRUPT_PROLOGUE so easier to
   refactor the common parts which is what this series aims to do

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARCv2: entry: comments about hardware auto-save on taken interrupts</title>
<updated>2023-08-11T09:45:10+00:00</updated>
<author>
<name>Vineet Gupta</name>
<email>vgupta@synopsys.com</email>
</author>
<published>2019-04-09T23:55:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5fe86ad6ae98d3fa19034eb7a43fd517af27ad2c'/>
<id>5fe86ad6ae98d3fa19034eb7a43fd517af27ad2c</id>
<content type='text'>
[ Upstream commit 45869eb0c0afd72bd5ab2437d4b00915697c044a ]

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 45869eb0c0afd72bd5ab2437d4b00915697c044a ]

Signed-off-by: Vineet Gupta &lt;vgupta@synopsys.com&gt;
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>arc: iounmap() arg is volatile</title>
<updated>2022-11-03T14:52:30+00:00</updated>
<author>
<name>Randy Dunlap</name>
<email>rdunlap@infradead.org</email>
</author>
<published>2022-10-10T02:28:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=13626e56d2f74a5803077cf76ac8ed71d5f7707a'/>
<id>13626e56d2f74a5803077cf76ac8ed71d5f7707a</id>
<content type='text'>
[ Upstream commit c44f15c1c09481d50fd33478ebb5b8284f8f5edb ]

Add 'volatile' to iounmap()'s argument to prevent build warnings.
This make it the same as other major architectures.

Placates these warnings: (12 such warnings)

../drivers/video/fbdev/riva/fbdev.c: In function 'rivafb_probe':
../drivers/video/fbdev/riva/fbdev.c:2067:42: error: passing argument 1 of 'iounmap' discards 'volatile' qualifier from pointer target type [-Werror=discarded-qualifiers]
 2067 |                 iounmap(default_par-&gt;riva.PRAMIN);

Fixes: 1162b0701b14b ("ARC: I/O and DMA Mappings")
Signed-off-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Cc: Vineet Gupta &lt;vgupta@kernel.org&gt;
Cc: linux-snps-arc@lists.infradead.org
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit c44f15c1c09481d50fd33478ebb5b8284f8f5edb ]

Add 'volatile' to iounmap()'s argument to prevent build warnings.
This make it the same as other major architectures.

Placates these warnings: (12 such warnings)

../drivers/video/fbdev/riva/fbdev.c: In function 'rivafb_probe':
../drivers/video/fbdev/riva/fbdev.c:2067:42: error: passing argument 1 of 'iounmap' discards 'volatile' qualifier from pointer target type [-Werror=discarded-qualifiers]
 2067 |                 iounmap(default_par-&gt;riva.PRAMIN);

Fixes: 1162b0701b14b ("ARC: I/O and DMA Mappings")
Signed-off-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Cc: Vineet Gupta &lt;vgupta@kernel.org&gt;
Cc: linux-snps-arc@lists.infradead.org
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARC: entry: fix syscall_trace_exit argument</title>
<updated>2022-04-27T11:39:45+00:00</updated>
<author>
<name>Sergey Matyukevich</name>
<email>sergey.matyukevich@synopsys.com</email>
</author>
<published>2022-04-14T08:17:22+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=f6331cd8f57d3b1876ba7a27bc4705cfcfb84de5'/>
<id>f6331cd8f57d3b1876ba7a27bc4705cfcfb84de5</id>
<content type='text'>
commit b1c6ecfdd06907554518ec384ce8e99889d15193 upstream.

Function syscall_trace_exit expects pointer to pt_regs. However
r0 is also used to keep syscall return value. Restore pointer
to pt_regs before calling syscall_trace_exit.

Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Sergey Matyukevich &lt;sergey.matyukevich@synopsys.com&gt;
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit b1c6ecfdd06907554518ec384ce8e99889d15193 upstream.

Function syscall_trace_exit expects pointer to pt_regs. However
r0 is also used to keep syscall return value. Restore pointer
to pt_regs before calling syscall_trace_exit.

Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Sergey Matyukevich &lt;sergey.matyukevich@synopsys.com&gt;
Signed-off-by: Vineet Gupta &lt;vgupta@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>arch: pgtable: define MAX_POSSIBLE_PHYSMEM_BITS where needed</title>
<updated>2021-11-06T12:58:45+00:00</updated>
<author>
<name>Arnd Bergmann</name>
<email>arnd@arndb.de</email>
</author>
<published>2020-11-11T16:52:58+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=d4fe42d646f277dfbc8a6cbc82bc4c8a12dd7798'/>
<id>d4fe42d646f277dfbc8a6cbc82bc4c8a12dd7798</id>
<content type='text'>
commit cef397038167ac15d085914493d6c86385773709 upstream.

Stefan Agner reported a bug when using zsram on 32-bit Arm machines
with RAM above the 4GB address boundary:

  Unable to handle kernel NULL pointer dereference at virtual address 00000000
  pgd = a27bd01c
  [00000000] *pgd=236a0003, *pmd=1ffa64003
  Internal error: Oops: 207 [#1] SMP ARM
  Modules linked in: mdio_bcm_unimac(+) brcmfmac cfg80211 brcmutil raspberrypi_hwmon hci_uart crc32_arm_ce bcm2711_thermal phy_generic genet
  CPU: 0 PID: 123 Comm: mkfs.ext4 Not tainted 5.9.6 #1
  Hardware name: BCM2711
  PC is at zs_map_object+0x94/0x338
  LR is at zram_bvec_rw.constprop.0+0x330/0xa64
  pc : [&lt;c0602b38&gt;]    lr : [&lt;c0bda6a0&gt;]    psr: 60000013
  sp : e376bbe0  ip : 00000000  fp : c1e2921c
  r10: 00000002  r9 : c1dda730  r8 : 00000000
  r7 : e8ff7a00  r6 : 00000000  r5 : 02f9ffa0  r4 : e3710000
  r3 : 000fdffe  r2 : c1e0ce80  r1 : ebf979a0  r0 : 00000000
  Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
  Control: 30c5383d  Table: 235c2a80  DAC: fffffffd
  Process mkfs.ext4 (pid: 123, stack limit = 0x495a22e6)
  Stack: (0xe376bbe0 to 0xe376c000)

As it turns out, zsram needs to know the maximum memory size, which
is defined in MAX_PHYSMEM_BITS when CONFIG_SPARSEMEM is set, or in
MAX_POSSIBLE_PHYSMEM_BITS on the x86 architecture.

The same problem will be hit on all 32-bit architectures that have a
physical address space larger than 4GB and happen to not enable sparsemem
and include asm/sparsemem.h from asm/pgtable.h.

After the initial discussion, I suggested just always defining
MAX_POSSIBLE_PHYSMEM_BITS whenever CONFIG_PHYS_ADDR_T_64BIT is
set, or provoking a build error otherwise. This addresses all
configurations that can currently have this runtime bug, but
leaves all other configurations unchanged.

I looked up the possible number of bits in source code and
datasheets, here is what I found:

 - on ARC, CONFIG_ARC_HAS_PAE40 controls whether 32 or 40 bits are used
 - on ARM, CONFIG_LPAE enables 40 bit addressing, without it we never
   support more than 32 bits, even though supersections in theory allow
   up to 40 bits as well.
 - on MIPS, some MIPS32r1 or later chips support 36 bits, and MIPS32r5
   XPA supports up to 60 bits in theory, but 40 bits are more than
   anyone will ever ship
 - On PowerPC, there are three different implementations of 36 bit
   addressing, but 32-bit is used without CONFIG_PTE_64BIT
 - On RISC-V, the normal page table format can support 34 bit
   addressing. There is no highmem support on RISC-V, so anything
   above 2GB is unused, but it might be useful to eventually support
   CONFIG_ZRAM for high pages.

Fixes: 61989a80fb3a ("staging: zsmalloc: zsmalloc memory allocation library")
Fixes: 02390b87a945 ("mm/zsmalloc: Prepare to variable MAX_PHYSMEM_BITS")
Acked-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Reviewed-by: Stefan Agner &lt;stefan@agner.ch&gt;
Tested-by: Stefan Agner &lt;stefan@agner.ch&gt;
Acked-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Link: https://lore.kernel.org/linux-mm/bdfa44bf1c570b05d6c70898e2bbb0acf234ecdf.1604762181.git.stefan@agner.ch/
Signed-off-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
[florian: patch arch/powerpc/include/asm/pte-common.h for 4.19.y]
Signed-off-by: Florian Fainelli &lt;f.fainelli@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
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commit cef397038167ac15d085914493d6c86385773709 upstream.

Stefan Agner reported a bug when using zsram on 32-bit Arm machines
with RAM above the 4GB address boundary:

  Unable to handle kernel NULL pointer dereference at virtual address 00000000
  pgd = a27bd01c
  [00000000] *pgd=236a0003, *pmd=1ffa64003
  Internal error: Oops: 207 [#1] SMP ARM
  Modules linked in: mdio_bcm_unimac(+) brcmfmac cfg80211 brcmutil raspberrypi_hwmon hci_uart crc32_arm_ce bcm2711_thermal phy_generic genet
  CPU: 0 PID: 123 Comm: mkfs.ext4 Not tainted 5.9.6 #1
  Hardware name: BCM2711
  PC is at zs_map_object+0x94/0x338
  LR is at zram_bvec_rw.constprop.0+0x330/0xa64
  pc : [&lt;c0602b38&gt;]    lr : [&lt;c0bda6a0&gt;]    psr: 60000013
  sp : e376bbe0  ip : 00000000  fp : c1e2921c
  r10: 00000002  r9 : c1dda730  r8 : 00000000
  r7 : e8ff7a00  r6 : 00000000  r5 : 02f9ffa0  r4 : e3710000
  r3 : 000fdffe  r2 : c1e0ce80  r1 : ebf979a0  r0 : 00000000
  Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
  Control: 30c5383d  Table: 235c2a80  DAC: fffffffd
  Process mkfs.ext4 (pid: 123, stack limit = 0x495a22e6)
  Stack: (0xe376bbe0 to 0xe376c000)

As it turns out, zsram needs to know the maximum memory size, which
is defined in MAX_PHYSMEM_BITS when CONFIG_SPARSEMEM is set, or in
MAX_POSSIBLE_PHYSMEM_BITS on the x86 architecture.

The same problem will be hit on all 32-bit architectures that have a
physical address space larger than 4GB and happen to not enable sparsemem
and include asm/sparsemem.h from asm/pgtable.h.

After the initial discussion, I suggested just always defining
MAX_POSSIBLE_PHYSMEM_BITS whenever CONFIG_PHYS_ADDR_T_64BIT is
set, or provoking a build error otherwise. This addresses all
configurations that can currently have this runtime bug, but
leaves all other configurations unchanged.

I looked up the possible number of bits in source code and
datasheets, here is what I found:

 - on ARC, CONFIG_ARC_HAS_PAE40 controls whether 32 or 40 bits are used
 - on ARM, CONFIG_LPAE enables 40 bit addressing, without it we never
   support more than 32 bits, even though supersections in theory allow
   up to 40 bits as well.
 - on MIPS, some MIPS32r1 or later chips support 36 bits, and MIPS32r5
   XPA supports up to 60 bits in theory, but 40 bits are more than
   anyone will ever ship
 - On PowerPC, there are three different implementations of 36 bit
   addressing, but 32-bit is used without CONFIG_PTE_64BIT
 - On RISC-V, the normal page table format can support 34 bit
   addressing. There is no highmem support on RISC-V, so anything
   above 2GB is unused, but it might be useful to eventually support
   CONFIG_ZRAM for high pages.

Fixes: 61989a80fb3a ("staging: zsmalloc: zsmalloc memory allocation library")
Fixes: 02390b87a945 ("mm/zsmalloc: Prepare to variable MAX_PHYSMEM_BITS")
Acked-by: Thomas Bogendoerfer &lt;tsbogend@alpha.franken.de&gt;
Reviewed-by: Stefan Agner &lt;stefan@agner.ch&gt;
Tested-by: Stefan Agner &lt;stefan@agner.ch&gt;
Acked-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Link: https://lore.kernel.org/linux-mm/bdfa44bf1c570b05d6c70898e2bbb0acf234ecdf.1604762181.git.stefan@agner.ch/
Signed-off-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
[florian: patch arch/powerpc/include/asm/pte-common.h for 4.19.y]
Signed-off-by: Florian Fainelli &lt;f.fainelli@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
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