From 7f049fbdd57f6ea71dc741d903c19c73b2f70950 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 11 Jun 2021 15:03:16 +0200 Subject: [PATCH] perf/x86/intel/lbr: Zero the xstate buffer on allocation 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 Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/87wnr0wo2z.ffs@nanos.tec.linutronix.de --- 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 4409d2cccfda..e8453de7a964 100644 --- a/arch/x86/events/intel/lbr.c +++ b/arch/x86/events/intel/lbr.c @@ -731,7 +731,8 @@ 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)); } }