linux-kernel - Re: [patch 4/8] PCI/MSI: Enforce MSI[X] entry updates to be visible

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Message-ID: <20210722214843.GA350177@bjorn-Precision-5520>
Date:   Thu, 22 Jul 2021 16:48:43 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Kevin Tian <kevin.tian@...el.com>,
        Marc Zyngier <maz@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        x86@...nel.org
Subject: Re: [patch 4/8] PCI/MSI: Enforce MSI[X] entry updates to be visible

On Wed, Jul 21, 2021 at 09:11:30PM +0200, Thomas Gleixner wrote:
> Nothing enforces the posted writes to be visible when the function
> returns. Flush them even if the flush might be redundant when the entry is
> masked already as the unmask will flush as well. This is either setup or a
> rare affinity change event so the extra flush is not the end of the world.
> 
> While this is more a theoretical issue especially the X86 MSI affinity
> stter mechanism relies on the assumption that the update has reached the

stter?

> hardware when the function returns.
> 
> Again, as this never has been enfocred the Fixes tag refers to a commit in:

s/enfocred/enforced/

>    git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git