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    Subject[17/85] x86, amd: Use _safe() msr access for GartTlbWlk disable code
    2.6.33-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    From: "Roedel, Joerg" <Joerg.Roedel@amd.com>

    commit d47cc0db8fd6011de2248df505fc34990b7451bf upstream.

    The workaround for Bugzilla:

    https://bugzilla.kernel.org/show_bug.cgi?id=33012

    introduced a read and a write to the MC4 mask msr.

    Unfortunatly this MSR is not emulated by the KVM hypervisor
    so that the kernel will get a #GP and crashes when applying
    this workaround when running inside KVM.

    This issue was reported as:

    https://bugzilla.kernel.org/show_bug.cgi?id=35132

    and is fixed with this patch. The change just let the kernel
    ignore any #GP it gets while accessing this MSR by using the
    _safe msr access methods.

    Reported-by: Török Edwin <edwintorok@gmail.com>
    Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
    Cc: Rafael J. Wysocki <rjw@sisk.pl>
    Cc: Maciej Rutecki <maciej.rutecki@gmail.com>
    Cc: Avi Kivity <avi@redhat.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/kernel/cpu/amd.c | 9 ++++++---
    1 file changed, 6 insertions(+), 3 deletions(-)

    --- a/arch/x86/kernel/cpu/amd.c
    +++ b/arch/x86/kernel/cpu/amd.c
    @@ -585,10 +585,13 @@ static void __cpuinit init_amd(struct cp
    * Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=33012
    */
    u64 mask;
    + int err;

    - rdmsrl(MSR_AMD64_MCx_MASK(4), mask);
    - mask |= (1 << 10);
    - wrmsrl(MSR_AMD64_MCx_MASK(4), mask);
    + err = rdmsrl_safe(MSR_AMD64_MCx_MASK(4), &mask);
    + if (err == 0) {
    + mask |= (1 << 10);
    + checking_wrmsrl(MSR_AMD64_MCx_MASK(4), mask);
    + }
    }
    }


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