linux-kernel - Re: [PATCH v2] KVM: x86: Always set kvm_run->if

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Date:   Thu, 9 Dec 2021 18:48:22 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Marc Orr <marcorr@...gle.com>, seanjc@...gle.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, thomas.lendacky@....com, mlevitsk@...hat.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: x86: Always set kvm_run->if_flag

On 12/9/21 16:52, Marc Orr wrote:
> The kvm_run struct's if_flag is a part of the userspace/kernel API. The
> SEV-ES patches failed to set this flag because it's no longer needed by
> QEMU (according to the comment in the source code). However, other
> hypervisors may make use of this flag. Therefore, set the flag for
> guests with encrypted registers (i.e., with guest_state_protected set).
> 
> Fixes: f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under SEV-ES")
> Signed-off-by: Marc Orr<marcorr@...gle.com>

Applied, though I wonder if it is really needed by those other VMMs 
(which? gVisor is the only one that comes to mind that is interested in 
userspace APIC).

It shouldn't be necessary for in-kernel APIC (where userspace can inject 
interrupts at any time), and ready_for_interrupt_injection is superior 
for userspace APIC.

Paolo