POWER: Add context-synchronizing instructions to pkey_write [BZ #25954]
Commit Message
Sandipan Das reported that,
"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.
This [requirement] 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>
"
See this kernel patch submission:
<https://lore.kernel.org/linuxppc-dev/5f65cf37be993760de8112a88da194e3ccbb2bf8.1588959697.git.sandipan@linux.ibm.com/>
Tested on powerpc64le-linux-gnu on a POWER9 system with disable_radix
and a compatible kernel (kernel-4.18.0-193.el8.ppc64le).
-----
sysdeps/unix/sysv/linux/powerpc/powerpc64/arch-pkey.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Comments
On 5/11/20 5:12 AM, Florian Weimer via Libc-alpha wrote:
> @@ -37,7 +37,7 @@ pkey_read (void)
> static inline void
> pkey_write (unsigned long int value)
> {
> - __asm__ volatile ("mtspr 13, %0" : : "r" (value));
> + __asm__ volatile ("isync; mtspr 13, %0; isync" : : "r" (value));
> }
>
> /* Number of the largest supported key. This depends on the width of
LGTM.
Thanks Florian.
LGTM
---
Lucas A. M. Magalhães
@@ -37,7 +37,7 @@ pkey_read (void)
static inline void
pkey_write (unsigned long int value)
{
- __asm__ volatile ("mtspr 13, %0" : : "r" (value));
+ __asm__ volatile ("isync; mtspr 13, %0; isync" : : "r" (value));
}
/* Number of the largest supported key. This depends on the width of