linux-kernel - Re: [v2 PATCH 3/4] x86/kvm: Add host side support for virtual suspend time injection

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Message-ID: <87o89vksiq.fsf@vitty.brq.redhat.com>
Date:   Wed, 18 Aug 2021 11:32:13 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     suleiman@...gle.com, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        John Stultz <john.stultz@...aro.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        x86@...nel.org, Hikaru Nishida <hikalium@...omium.org>,
        linux-kernel@...r.kernel.org, dme@....org, tglx@...utronix.de,
        mlevitsk@...hat.com
Subject: Re: [v2 PATCH 3/4] x86/kvm: Add host side support for virtual
 suspend time injection

Paolo Bonzini <pbonzini@...hat.com> writes:

> On 06/08/21 12:07, Hikaru Nishida wrote:
>> +#if defined(CONFIG_KVM_VIRT_SUSPEND_TIMING) || \
>> +	defined(CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST)
>> +#define VIRT_SUSPEND_TIMING_VECTOR	0xec
>> +#endif
>
> No need to use a new vector.  You can rename the existing 
> MSR_KVM_ASYNC_PF_INT to MSR_KVM_HYPERVISOR_CALLBACK_INT or something 
> like that, and add the code to sysvec_kvm_asyncpf_interrupt.

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).

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

-- 
Vitaly