Messages in this thread Patch in this message | | | From | Sasha Levin <> | Subject | [PATCH 5.10 021/101] perf/x86/intel/lbr: Zero the xstate buffer on allocation | Date | Mon, 28 Jun 2021 10:24:47 -0400 |
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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)); } } -- 2.30.2
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