linux-kernel - RE: [PATCH] KVM: x86: always exit on EOIs for interrupts listed in the IOAPIC redir table

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Date:	Thu, 7 Aug 2014 06:17:53 +0000
From:	"Zhang, Yang Z" <yang.z.zhang@...el.com>
To:	Paolo Bonzini <pbonzini@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] KVM: x86: always exit on EOIs for interrupts listed in
 the IOAPIC redir table

Paolo Bonzini wrote on 2014-08-07:
> Il 07/08/2014 03:31, Zhang, Yang Z ha scritto:
>> Let me give an example to see whether my concern is a real problem:
>> Guest allocates a vector and set it in IOAPIC entry to deliver
>> interrupt. Later it masks the IOAPIC entry(means stop the
>> corresponding device) and assign this vector to a MSI device. With
>> this patch, even the vector is not used by IOAPIC, but it still set
>> eoi exit bitmap unconditionally. The subsequent EOIs to MSI device
>> will force vmexit. Could this happen?
> 
> Yes, I guess it could.  I'm not sure whether it could on Linux or Windows.
> 
>> I think the right fixing is to check the ISR plus TMR to construct
>> the eoi exit bitmap.
> 
> Do you care enough to propose a patch? :)
> 

Sure. I will do it.

> Paolo


Best regards,
Yang

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