lkml.org 
[lkml]   [2015]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] mce: use safe MSR accesses

On 03/13/2015 11:03 AM, jesse.larrew@amd.com wrote:
> From: Jesse Larrew <jesse.larrew@amd.com>
>
> Certain MSRs are only relevant to a kernel in host mode, and kvm had
> chosen not to implement these MSRs at all for guests. If a guest kernel
> ever tried to access these MSRs, the result was a general protection
> fault.
>
> KVM will be separately patched to return 0 when these MSRs are read,
> and this patch ensures that MSR accesses are tolerant of exceptions.
>
> Signed-off-by: Jesse Larrew <jesse.larrew@amd.com>
> ---
> arch/x86/kernel/cpu/mcheck/mce.c | 11 +++--------
> 1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 61a9668ce..2737ced 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -1540,7 +1540,7 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
> if (c->x86 == 0x15 &&
> (c->x86_model >= 0x10 && c->x86_model <= 0x1f)) {
> int i;
> - u64 val, hwcr;
> + u64 hwcr;
> bool need_toggle;
> u32 msrs[] = {
> 0x00000413, /* MC4_MISC0 */
> @@ -1556,13 +1556,8 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
> wrmsrl(MSR_K7_HWCR, hwcr | BIT(18));
>
> for (i = 0; i < ARRAY_SIZE(msrs); i++) {
> - rdmsrl(msrs[i], val);
> -
> - /* CntP bit set? */
> - if (val & BIT_64(62)) {
> - val &= ~BIT_64(62);
> - wrmsrl(msrs[i], val);
> - }
> + /* Clear CntP bit safely */
> + msr_clear_bit(msrs[i], 62);
> }
>
> /* restore old settings */
I like it.

Reviewed-by: Joel Schopp <joel.schopp@amd.com>


\
 
 \ /
  Last update: 2015-03-13 18:01    [W:0.033 / U:8.268 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site