linux-kernel - Re: [PART1 RFC v2 07/10] svm: Add VMEXIT handlers for AVIC

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Date:	Thu, 17 Mar 2016 10:35:05 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Radim Krčmář <rkrcmar@...hat.com>
Cc:	joro@...tes.org, bp@...en8.de, gleb@...nel.org,
	alex.williamson@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, wei@...hat.com,
	sherry.hurwitz@....com
Subject: Re: [PART1 RFC v2 07/10] svm: Add VMEXIT handlers for AVIC



On 17/03/2016 04:58, Suravee Suthikulpanit wrote:
>>>
>>> >+    BUG_ON(offset >= 0x400);
>> These are valid faulting registers, so our implementation has to handle
>> them.  (And the rule is to never BUG if a recovery is simple.)
>>
> 
> Just want to clarify the part that you mentioned "to handle them". IIUC,
> offet 0x400 and above are for x2APIC stuff, which AVIC does not
> currently support. Also, since I have only advertised as xAPIC when
> enabling AVIC, if we run into the situation that the VM is trying to
> access these register, we should just ignore it (and not BUG). Do I
> understand that correctly?

Yes.  You can add a printk(KERN_DEBUG) though.

Paolo