Re: [PATCH 2/2] selftests: vm: pkeys: Fix powerpc access right updates

[Florian Weimer]

* 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:

  

Florian

Re: [PATCH 2/2] selftests: vm: pkeys: Fix powerpc access right updates

[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

- Sandipan

Re: [PATCH 2/2] selftests: vm: pkeys: Fix powerpc access right updates

[Florian Weimer]

* 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

[PATCH 2/2] selftests: vm: pkeys: Fix powerpc access right updates

[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.

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

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);
-- 
2.17.1