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:4.101 / U:0.164 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site