From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit 7f049fbdd57f6ea71dc741d903c19c73b2f70950 ]
XRSTORS requires a valid xstate buffer to work correctly. XSAVES does not guarantee to write a fully valid buffer according to the SDM:
"XSAVES does not write to any parts of the XSAVE header other than the XSTATE_BV and XCOMP_BV fields."
XRSTORS triggers a #GP:
"If bytes 63:16 of the XSAVE header are not all zero."
It's dubious at best how this can work at all when the buffer is not zeroed before use.
Allocate the buffers with __GFP_ZERO to prevent XRSTORS failure.
Fixes: ce711ea3cab9 ("perf/x86/intel/lbr: Support XSAVES/XRSTORS for LBR context switch") Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lore.kernel.org/r/87wnr0wo2z.ffs@nanos.tec.linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/events/intel/lbr.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c index 6c1231837382..29ec4fe48507 100644 --- a/arch/x86/events/intel/lbr.c +++ b/arch/x86/events/intel/lbr.c @@ -730,7 +730,8 @@ void reserve_lbr_buffers(void) if (!kmem_cache || cpuc->lbr_xsave) continue;
- cpuc->lbr_xsave = kmem_cache_alloc_node(kmem_cache, GFP_KERNEL, + cpuc->lbr_xsave = kmem_cache_alloc_node(kmem_cache, + GFP_KERNEL | __GFP_ZERO, cpu_to_node(cpu)); } }