linux-kernel - Re: [PART1 V5 13/13] svm: Manage vcpu load/unload when enable AVIC

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Date:	Wed, 1 Jun 2016 20:37:34 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	rkrcmar@...hat.com, joro@...tes.org, bp@...en8.de, gleb@...nel.org,
	alex.williamson@...hat.com
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, wei@...hat.com,
	sherry.hurwitz@....com
Subject: Re: [PART1 V5 13/13] svm: Manage vcpu load/unload when enable AVIC

On 01/06/2016 20:18, Suravee Suthikulpanit wrote:
>>>
>>> +    svm->avic_is_running = is_run;
> 
> Shouldn't we do this below --->
>>>
>>>       /* ID = 0xff (broadcast), ID > 0xff (reserved) */
>>> -    if (h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT)
>>> -        return -EINVAL;
>>> +    if (WARN_ON(h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT))
>>> +        return;
> 
> <--- HERE

It doesn't really matter because these physical APIC IDs are not
reachable anyway so they don't have the IS_RUNNING field.

The avic_is_running field is only used in avic_vcpu_load, and again only
when h_physical_id is in range.  I left the assignment before the
warning so that avic_vcpu_load does the right thing after a
(hypothetical) migration from an out-of-range physical CPU to an
in-range physical CPU.

Paolo