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

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Message-ID: <20160125140552.GB21252@potion.brq.redhat.com>
Date:	Mon, 25 Jan 2016 15:05:53 +0100
From:	Radim Krcmár <rkrcmar@...hat.com>
To:	"Wu, Feng" <feng.wu@...el.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 1/4] KVM: Recover IRTE to remapped mode if the
 interrupt is not single-destination

2016-01-25 12:26+0000, Wu, Feng:
>> From: Paolo Bonzini [mailto:paolo.bonzini@...il.com] 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 ...