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From: Paolo Bonzini <pbonzini@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: suleiman@google.com, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	John Stultz <john.stultz@linaro.org>,
	Sean Christopherson <seanjc@google.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Wanpeng Li <wanpengli@tencent.com>,
	kvm@vger.kernel.org, x86@kernel.org,
	Hikaru Nishida <hikalium@chromium.org>,
	linux-kernel@vger.kernel.org, dme@dme.org, tglx@linutronix.de,
	mlevitsk@redhat.com
Subject: Re: [v2 PATCH 3/4] x86/kvm: Add host side support for virtual suspend time injection
Date: Wed, 18 Aug 2021 22:49:05 +0200	[thread overview]
Message-ID: <89fa5648-e034-6435-9b21-a6ca0cb22a46@redhat.com> (raw)
In-Reply-To: <87o89vksiq.fsf@vitty.brq.redhat.com>

On 18/08/21 11:32, Vitaly Kuznetsov wrote:
> On the host side, I'd vote for keeping MSR_KVM_ASYNC_PF_INT for async PF
> mechanism only for two reasons:
> - We may want to use (currently reserved) upper 56 bits of it for new
> asyncPF related features (e.g. flags) and it would be unnatural to add
> them to 'MSR_KVM_HYPERVISOR_CALLBACK_INT'
> - We should probably leave it to the guest if it wants to share 'suspend
> time' notification interrupt with async PF (and if it actually wants to
> get one/another).

I agree that it's fine either way.  That said, more MSRs are more 
complexity and more opportunity for getting things wrong (in either KVM 
or userspace---for example, migration).  There are still 14 free bits in 
MSR_ASYNC_PF_EN (bits 63-52 and 5-4, so it should not be a problem to 
repurpose MSR_ASYNC_PF_INT.

Paolo

> On the guest side, it is perfectly fine to reuse
> HYPERVISOR_CALLBACK_VECTOR for everything.


  reply	other threads:[~2021-08-18 20:49 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-06 10:07 [v2 PATCH 0/4] x86/kvm: Virtual suspend time injection support Hikaru Nishida
2021-08-06 10:07 ` [v2 PATCH 1/4] x86/kvm: Reserve KVM_FEATURE_HOST_SUSPEND_TIME and MSR_KVM_HOST_SUSPEND_TIME Hikaru Nishida
2021-08-06 10:07 ` [v2 PATCH 2/4] x86/kvm: Add definitions for virtual suspend time injection Hikaru Nishida
2021-08-10 15:14   ` Thomas Gleixner
2021-08-13 18:36   ` Guenter Roeck
2021-08-06 10:07 ` [v2 PATCH 3/4] x86/kvm: Add host side support " Hikaru Nishida
2021-08-10 15:21   ` Thomas Gleixner
2021-08-10 15:24   ` Thomas Gleixner
2021-08-14  7:22   ` Paolo Bonzini
2021-08-18  9:32     ` Vitaly Kuznetsov
2021-08-18 20:49       ` Paolo Bonzini [this message]
2021-08-06 10:07 ` [v2 PATCH 4/4] x86/kvm: Add guest " Hikaru Nishida
2021-08-10 15:48   ` Thomas Gleixner

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