[2/2] selftests: vm: pkeys: Fix powerpc access right updates
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Message ID 5f65cf37be993760de8112a88da194e3ccbb2bf8.1588959697.git.sandipan@linux.ibm.com
State New
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Series
  • selftests: vm: pkeys: Some powerpc fixes
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Commit Message

Sandipan Das May 8, 2020, 5:49 p.m. UTC
The Power ISA mandates that all writes to the Authority
Mask Register (AMR) must always be preceded as well as
succeeded by a context-synchronizing instruction. This
applies to both the privileged and unprivileged variants
of the Move To AMR instruction.

Fixes: 130f573c2a79 ("selftests/vm/pkeys: introduce powerpc support")
Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Suggested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
---
 tools/testing/selftests/vm/pkey-powerpc.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Florian Weimer May 8, 2020, 6:01 p.m. UTC | #1
* Sandipan Das:

> The Power ISA mandates that all writes to the Authority
> Mask Register (AMR) must always be preceded as well as
> succeeded by a context-synchronizing instruction. This
> applies to both the privileged and unprivileged variants
> of the Move To AMR instruction.

Ugh.  Do you have a reference for that?

We need to fix this in glibc.

Thanks,
Florian
Sandipan Das May 8, 2020, 7:54 p.m. UTC | #2
Hi Florian,

On 08/05/20 11:31 pm, Florian Weimer wrote:
> * Sandipan Das:
> 
>> The Power ISA mandates that all writes to the Authority
>> Mask Register (AMR) must always be preceded as well as
>> succeeded by a context-synchronizing instruction. This
>> applies to both the privileged and unprivileged variants
>> of the Move To AMR instruction.
> 
> Ugh.  Do you have a reference for that?
> 
> We need to fix this in glibc.
> 

This is from Table 6 of Chapter 11 in page 1134 of Power
ISA 3.0B. The document can be found here:
https://ibm.ent.box.com/s/1hzcwkwf8rbju5h9iyf44wm94amnlcrv

- Sandipan
Florian Weimer May 8, 2020, 8:03 p.m. UTC | #3
* Sandipan Das:

> Hi Florian,
>
> On 08/05/20 11:31 pm, Florian Weimer wrote:
>> * Sandipan Das:
>> 
>>> The Power ISA mandates that all writes to the Authority
>>> Mask Register (AMR) must always be preceded as well as
>>> succeeded by a context-synchronizing instruction. This
>>> applies to both the privileged and unprivileged variants
>>> of the Move To AMR instruction.
>> 
>> Ugh.  Do you have a reference for that?
>> 
>> We need to fix this in glibc.
>> 
>
> This is from Table 6 of Chapter 11 in page 1134 of Power
> ISA 3.0B. The document can be found here:
> https://ibm.ent.box.com/s/1hzcwkwf8rbju5h9iyf44wm94amnlcrv

Thanks a lot!  I filed:

  <https://sourceware.org/bugzilla/show_bug.cgi?id=25954>

Florian

Patch
diff mbox series

diff --git a/tools/testing/selftests/vm/pkey-powerpc.h b/tools/testing/selftests/vm/pkey-powerpc.h
index eb5077de8f1e..1ebb586b2fbc 100644
--- a/tools/testing/selftests/vm/pkey-powerpc.h
+++ b/tools/testing/selftests/vm/pkey-powerpc.h
@@ -55,7 +55,8 @@  static inline void __write_pkey_reg(u64 pkey_reg)
 	dprintf4("%s() changing %016llx to %016llx\n",
 			 __func__, __read_pkey_reg(), pkey_reg);
 
-	asm volatile("mtspr 0xd, %0" : : "r" ((unsigned long)(amr)) : "memory");
+	asm volatile("isync; mtspr 0xd, %0; isync"
+		     : : "r" ((unsigned long)(amr)) : "memory");
 
 	dprintf4("%s() pkey register after changing %016llx to %016llx\n",
 			__func__, __read_pkey_reg(), pkey_reg);