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From: Paolo Bonzini <pbonzini@redhat.com>
To: "Suravee Suthikulpanit" <Suravee.Suthikulpanit@amd.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>
Cc: joro@8bytes.org, bp@alien8.de, gleb@kernel.org,
	alex.williamson@redhat.com, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, wei@redhat.com,
	sherry.hurwitz@amd.com
Subject: Re: [PART1 RFC v3 10/12] svm: Do not expose x2APIC when enable AVIC
Date: Thu, 31 Mar 2016 13:23:26 +0200	[thread overview]
Message-ID: <56FD08AE.6000201@redhat.com> (raw)
In-Reply-To: <56FCA468.8090406@amd.com>



On 31/03/2016 06:15, Suravee Suthikulpanit wrote:
>>> +                vcpu->arch.cpuid_entries[i].ecx &= ~(1 << 21);
>> 
>> and X86_FEATURE_X2APIC (or something with X2APIC in name) for the
>> bit.
>> 
>> The code will become so obvious that the comment can be removed.
>> :)
> 
> Good point. I can only find example of using (X86_FEATURE_X2APIC %
> 32) == 21.

You can use bit(X86_FEATURE_X2APIC), it is defined in arch/x86/kvm/x86.h.

>> but the MSR interface is going to exit and host-side interrupt 
>> delivery will probably still work, so I don't see a huge problem
>> with it.
> 
> Agree that it will still work. However, in such case, the guest code
> would likely default to using x2APIC interface, which will not be
> handled by the AVIC hardware, and resulting in no performance
> improvement that we are trying to introduce.

You would still get some improvement from exit-free interrupt delivery.

Paolo

  reply	other threads:[~2016-03-31 11:23 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-18  6:09 [PART1 RFC v3 00/12] KVM: x86: Introduce SVM AVIC support Suravee Suthikulpanit
2016-03-18  6:09 ` [PART1 RFC v3 01/12] KVM: x86: Misc LAPIC changes to expose helper functions Suravee Suthikulpanit
2016-03-18 11:16   ` Paolo Bonzini
2016-03-18  6:09 ` [PART1 RFC v3 02/12] KVM: x86: Introducing kvm_x86_ops VM init/uninit hooks Suravee Suthikulpanit
2016-03-18 10:11   ` Paolo Bonzini
2016-03-29  5:27     ` Suravee Suthikulpanit
2016-03-29 10:21       ` Paolo Bonzini
2016-03-29 11:47         ` Suravee Suthikulpanit
2016-03-30 10:00           ` Suravee Suthikulpanit
2016-03-30 12:07             ` Paolo Bonzini
2016-03-30 12:18               ` Suravee Suthikulpanit
2016-03-18  6:09 ` [PART1 RFC v3 03/12] KVM: x86: Introducing kvm_x86_ops VCPU blocking/unblocking hooks Suravee Suthikulpanit
2016-03-18 10:11   ` Paolo Bonzini
2016-03-18  6:09 ` [PART1 RFC v3 04/12] KVM: split kvm_vcpu_wake_up from kvm_vcpu_kick Suravee Suthikulpanit
2016-03-18 10:11   ` Paolo Bonzini
2016-03-18  6:09 ` [PART1 RFC v3 05/12] svm: Introduce new AVIC VMCB registers Suravee Suthikulpanit
2016-03-18 10:11   ` Paolo Bonzini
2016-03-18  6:09 ` [PART1 RFC v3 06/12] KVM: x86: Detect and Initialize AVIC support Suravee Suthikulpanit
2016-03-18 11:21   ` Paolo Bonzini
2016-03-18  6:09 ` [PART1 RFC v3 07/12] svm: Add interrupt injection via AVIC Suravee Suthikulpanit
2016-03-18 10:22   ` Paolo Bonzini
2016-04-05 13:26     ` Suravee Suthikulpanit
2016-04-05 15:56       ` Suravee Suthikulpanit
2016-03-18  6:09 ` [PART1 RFC v3 08/12] KVM: x86: Add trace events for AVIC Suravee Suthikulpanit
2016-03-18 10:24   ` Paolo Bonzini
2016-03-28 11:27     ` Suravee Suthikulpanit
2016-03-18  6:09 ` [PART1 RFC v3 09/12] svm: Add VMEXIT handlers " Suravee Suthikulpanit
2016-03-18 11:11   ` Paolo Bonzini
2016-03-18  6:09 ` [PART1 RFC v3 10/12] svm: Do not expose x2APIC when enable AVIC Suravee Suthikulpanit
2016-03-18 20:59   ` Radim Krčmář
2016-03-31  4:15     ` Suravee Suthikulpanit
2016-03-31 11:23       ` Paolo Bonzini [this message]
2016-04-05 10:14         ` Suravee Suthikulpanit
2016-03-18  6:09 ` [PART1 RFC v3 11/12] svm: Do not intercept CR8 " Suravee Suthikulpanit
2016-03-18 21:10   ` Radim Krčmář
2016-03-30 12:15     ` Suravee Suthikulpanit
2016-03-18  6:09 ` [PART1 RFC v3 12/12] svm: Manage vcpu load/unload " Suravee Suthikulpanit
2016-03-18 21:44   ` Radim Krčmář
2016-03-31  8:52     ` Suravee Suthikulpanit
2016-03-31 14:19       ` Radim Krčmář
2016-04-05 10:07         ` Suravee Suthikulpanit
2016-04-05 14:56           ` Radim Krčmář
2016-04-06  3:40             ` Suravee Suthikulpanit
2016-04-06 12:36               ` Radim Krčmář

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