Re: [PATCH 10/18] x86/asm/32: Pull MSR_IA32_SYSENTER_CS update code out of native_load_sp0()

Borislav Petkov
2017-10-27T20:11:52Z

On Thu, Oct 26, 2017 at 01:26:42AM -0700, Andy Lutomirski wrote:
> This causees the MSR_IA32_SYSENTER_CS write to move out of the

Spellcheck pls.

> paravirt hook. This shouldn't affect Xen PV: Xen already ignores
> MSR_IA32_SYSENTER_ESP writes. In any event, Xen doesn't support
> vm86() in a useful way.
>
> Note to any potential backporters: This patch won't break lguest, as
> lguest didn't have any SYSENTER support at all.

...

> diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
> index 11966251cd42..84d6c9f554d0 100644
> --- a/arch/x86/kernel/process_32.c
> +++ b/arch/x86/kernel/process_32.c
> @@ -287,6 +287,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
> * current_thread_info().
> */
> load_sp0(tss, next);
> + refresh_sysenter_cs(next); /* in case prev or next is vm86 */

Ewww, side comments.

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Regards/Gruss,
Boris.

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