linux-kernel - Re: [PATCH 1/8] x86/irq: Ensure initial PIR loads are performed exactly once

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Message-ID: <871puv6guk.ffs@tglx>
Date: Mon, 17 Mar 2025 12:23:31 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Sean Christopherson <seanjc@...gle.com>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, Jacob Pan
 <jacob.jun.pan@...ux.intel.com>, Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH 1/8] x86/irq: Ensure initial PIR loads are performed
 exactly once

On Fri, Mar 14 2025 at 20:06, Sean Christopherson wrote:
> Ensure the PIR is read exactly once at the start of handle_pending_pir(),
> to guarantee that checking for an outstanding posted interrupt in a given
> chuck doesn't reload the chunk from the "real" PIR.  Functionally, a reload
> is benign, but it would defeat the purpose of pre-loading into a copy.
>
> Fixes: 1b03d82ba15e ("x86/irq: Install posted MSI notification handler")
> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>