Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the interrupt is not single-destination

From: Radim KrcmÃr
Date: Mon Jan 25 2016 - 09:06:03 EST

2016-01-25 12:26+0000, Wu, Feng:
>> From: Paolo Bonzini [mailto:paolo.bonzini@xxxxxxxxx] On Behalf Of Paolo
>> It may be necessary because IRTE writes (128 bits) are not atomic.
> IRTE is updated atomically, I added the patch to support this. Please
> refer to 344cb4e0b6f3a0dbef0643eacb4946338eb228c0.

I also think that SN bit is not affected by atomicity: if the IRTE could
have been read half-updated while changing from posted to non-posted,
then it wouldn't point to the correct PID, because its address is not
within 64 bits, so the SN bit wouldn't matter.

IRTE invalidation seems important in VT-d ...