linux-kernel - Re: [PART1 RFC v2 06/10] svm: Add interrupt injection via AVIC

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Message-ID: <56E6874E.4010807@amd.com>
Date:	Mon, 14 Mar 2016 16:41:34 +0700
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Radim Krčmář <rkrcmar@...hat.com>,
	Paolo Bonzini <pbonzini@...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 06/10] svm: Add interrupt injection via AVIC

Hi

On 03/09/2016 11:00 PM, Radim Krčmář wrote:
> 2016-03-09 12:10+0100, Paolo Bonzini:
>> On 08/03/2016 22:54, Radim Krčmář wrote:
>>> 2016-03-07 16:36+0100, Paolo Bonzini:
>>>> On 04/03/2016 21:46, Suravee Suthikulpanit wrote:
>>>>> +static void svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec)
>>>>> +{
>>>>> +	struct vcpu_svm *svm = to_svm(vcpu);
>>>>> +
>>>>> +	kvm_lapic_set_vector(vec, avic_get_bk_page_entry(svm, APIC_IRR));
>>>
>>> (I think that smp_mb here would make sense, even though we're fine now
>>>   thanks to re-checking vcpu->mode in kvm_vcpu_kick.
>>
>> Right, though only a smp_mb__after_atomic() is required (which is a
>> compiler barrier).  It is similarly required in vmx.
>
> True, kvm_lapic_set_vector uses a lock prefix.
>
> (I thought it behaves like atomic_set, which would require MFENCE for
>   correct ordering here ... I don't like smp_mb__after_atomic much
>   because of the discrepancy on some atomic operations.)
>

So, should i just use smb_mb() in this case?

Suravee.