Re: [Xen-devel] [PATCH v6 05/10] Clear AC bit in RFLAGS to protect Xen itself by SMAP

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.05.14 at 11:44, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 07/05/14 09:19, Feng Wu wrote:
>> @@ -673,6 +675,7 @@ ENTRY(nmi_crash)
>>          ud2
>>  
>>  ENTRY(machine_check)
>> +        ASM_CLAC
> 
> This is not needed.  the start of handle_ist_exception has a SAVE_ALL,
> which also covers the nmi entry point.
> 
> On the subject of IST exceptions, perhaps the double fault explicitly
> wants a STAC to reduce the likelihood of taking a further fault while
> trying to dump state. ?

I agree. And perhaps along with do_double_fault(), fatal_trap()
should then also get a stac() added?

Jan


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