lkml.org 
[lkml]   [2021]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.10 021/101] perf/x86/intel/lbr: Zero the xstate buffer on allocation
Date
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
\
 
 \ /
  Last update: 2021-06-28 16:35    [W:0.805 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site