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

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Date:	Fri, 18 Mar 2016 02:44:24 +0700
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Radim Krčmář <rkrcmar@...hat.com>
CC:	<pbonzini@...hat.com>, <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

Hi,

On 3/10/16 03:55, Radim Krčmář wrote:
> 2016-03-04 14:46-0600, Suravee Suthikulpanit:
>> >From: Suravee Suthikulpanit<suravee.suthikulpanit@....com>
>> >
>> >Introduce VMEXIT handlers, avic_incp_ipi_interception() and
>> >avic_noaccel_interception().
>> >
>> >Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@....com>
>> >---
>> >diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> >@@ -3690,6 +3690,264 @@ static int mwait_interception(struct vcpu_svm *svm)
>> >+	case AVIC_INCMP_IPI_ERR_TARGET_NOT_RUN: {
>> >+		kvm_for_each_vcpu(i, vcpu, kvm) {
>> >+			if (!kvm_apic_match_dest(vcpu, apic,
>> >+						 icrl & APIC_SHORT_MASK,
>> >+						 GET_APIC_DEST_FIELD(icrh),
>> >+						 icrl & APIC_DEST_MASK))
>> >+				continue;
>> >+
>> >+			kvm_vcpu_kick(vcpu);
> KVM shouldn't kick VCPUs that are running.  (Imagine a broadcast when
> most VCPUs are in guest mode.)

So, besides checking if the vcpu match the destination, I will add the 
check to see if the is_running bit is set before calling kvm_vcpu_kick()

> I think a new helper might be useful here: we only want to wake up from
> wait queue, but never force VCPU out of guest mode ... kvm_vcpu_kick()
> does both.

If I only kick non-running vcpu, do I still need this new helper function?

Thanks,
Suravee