linux-kernel - Re: [PATCH v3] KVM: selftests: Test TPR / CR8 sync and interrupt masking

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aPJqToq-589NovVS@google.com>
Date: Fri, 17 Oct 2025 09:09:50 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Naveen N Rao <naveen@...nel.org>, 
	Maxim Levitsky <mlevitsk@...hat.com>, Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>, 
	Alejandro Jimenez <alejandro.j.jimenez@...cle.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] KVM: selftests: Test TPR / CR8 sync and interrupt masking

On Fri, Oct 17, 2025, Maciej S. Szmigiero wrote:
> On 25.09.2025 12:43, Naveen N Rao wrote:
> > On Tue, Sep 23, 2025 at 07:32:14PM +0200, Maciej S. Szmigiero 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>
> > 
> 
> Was this patch picked up or are there any other review comments here?
> I can't seem to find it in any KVM upstream tree.

Not applied yet, though it's in my queue to look at.

The main reason for the delay is that I think I made a mistake by shoving the ICR
test into xapic_state_test.c. Bundling the ICR test with APIC ID tests was "fine"
at the time, but it obviously encourages using the test as a dumping ground for
similar APIC tests.  And I don't want selftests to end up like KUT where there
are these huge, inscrutable tests that are painful to debug.

So I don't want to apply this patch before deciding whether or not to split
xapic_state_test.c, e.g. into xapic_id_test.c and xapic_icr_test.c, and then
this could add xapic_tpr_test.c.  But I haven't looked closely enough at your
patch to make a concrete suggestion (at a glance, it looks like there's not much
overlap with the ICR test, so I'm leaning strongly towards splitting).