Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*

H. Peter Anvin
2014-04-22T18:52:21Z

On 04/22/2014 11:17 AM, Brian Gerst wrote:
>>
>> That is the entry condition that we have to deal with. The fact that
>> the switch to the IST is unconditional is what makes ISTs hard to deal with.
>
> Right, that is why you switch away from the IST as soon as possible,
> copying the data that is already pushed there to another stack so it
> won't be overwritten by a recursive fault.
>

That simply will not work if you can take a #GP due to the "safe" MSR
functions from NMI and #MC context, which would be my main concern.

-hpa