linux-kernel - Re: [PATCH v4] KVM: selftests: Test TPR / CR8 sync and interrupt masking

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Message-ID: <83f2685c-c683-4b6c-8af4-ca450a34fe51@maciej.szmigiero.name>
Date: Mon, 8 Dec 2025 22:11:53 +0100
From: "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
 linux-kernel@...r.kernel.org, Naveen N Rao <naveen@...nel.org>
Subject: Re: [PATCH v4] KVM: selftests: Test TPR / CR8 sync and interrupt
 masking

On 5.12.2025 23:49, Sean Christopherson wrote:
> From: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
> 
> Add a few extra TPR / CR8 tests to x86's xapic_state_test to see if:
>    * TPR is 0 on reset,
>    * TPR, PPR and CR8 are equal inside the guest,
>    * TPR and CR8 read equal by the host after a VMExit
>    * TPR borderline values set by the host correctly mask interrupts in the
>      guest.
> 
> These hopefully will catch the most obvious cases of improper TPR sync or
> interrupt masking.
> 
> Do these tests both in x2APIC and xAPIC modes.
> The x2APIC mode uses SELF_IPI register to trigger interrupts to give it a
> bit of exercise too.
> 
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@...cle.com>
> Acked-by: Naveen N Rao (AMD) <naveen@...nel.org>
> [sean: put code in separate test]
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> 
> Maciej's TPR test.  The only change relative to v3 (well, the only intended
> change :-D) is to move the testcase to its own test.  IMO, it's cleaner for
> both this test and the existing xapic_state_test (which I plan on splitting
> up at some point).
> 
Thanks Sean for the updated test.

I see that besides the TPR testcase being separated into its own test some
things were renamed and also GUEST_SYNC() parameter meaning was inverted.

Anyway, I re-tested the separated test (including on a kernel that's un-fixed
with respect to the AVIC TPR sync to make it fail) and the test still seems
to do its job properly.

Thanks,
Maciej