Re: [Xen-devel] [PATCH v6 08/10] x86: Enable Supervisor Mode Access Prevention (SMAP) for Xen

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.05.14 at 08:25, <feng.wu@xxxxxxxxx> wrote:
>> From: Tian, Kevin
>> could you double-check whether S3 resume and CPU hotplug are covered
>> well?
>> 
> Kevin, thank you very much for point this out!
> 
> I checked the following code path:
> wakeup_start --> wakeup_32 --> wakeup_64 --> __ret_point --> 
> restore_rest_processor_state()
> 
> I thought there was nothing special to do with SMAP here, but after careful 
> review, I think we should
> set X86_EFLAGS_AC for MSR_SYSCALL_MASK in restore_rest_processor_state(), 
> which can
> make AC bit cleared when entering kernel mode via SYSCALL after S3 resume. 
> However, I think this
> change should be included in patch "Clear AC bit in RFLAGS to protect Xen 
> itself by SMAP",
> in which, we did the same thing for MSR_SYSCALL_MASK in 
> subarch_percpu_traps_init().

Yes, that's indeed where it should be done.

Jan


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