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Date: Tue, 31 Mar 2026 14:02:16 -0500
From: Bjorn Helgaas <helgaas@kernel.org>
To: David Matlack <dmatlack@google.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	Alexander Lobakin <aleksander.lobakin@intel.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Bartosz Pawlowski <bartosz.pawlowski@intel.com>,
	David Woodhouse <dwmw2@infradead.org>, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, Lu Baolu <baolu.lu@linux.intel.com>,
	Raghavendra Rao Ananta <rananta@google.com>
Subject: Re: [PATCH v2] PCI: Disable ATS via quirk before notifying IOMMU
 drivers
Message-ID: <20260331190216.GA151735@bhelgaas>
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In-Reply-To: <CALzav=daA0ut2FE-Y07WtYoj45afVte=kh=SNegQ=wGyD+tWvQ@mail.gmail.com>

On Tue, Mar 31, 2026 at 11:46:22AM -0700, David Matlack wrote:
> On Tue, Mar 31, 2026 at 11:38 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > On Tue, Mar 31, 2026 at 09:01:53AM -0700, David Matlack wrote:
> > > On Fri, Mar 27, 2026 at 2:17 PM David Matlack <dmatlack@google.com> wrote:
> > >
> > > >  /* AMD Raven platform iGPU */
> > > > -DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x15d8, quirk_amd_harvest_no_ats);
> > > > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_ATI, 0x15d8, quirk_amd_harvest_no_ats);
> > >
> > > Sashiko found a bug here that would leave ATS enabled on this device:
> > >
> > >   https://sashiko.dev/#/patchset/20260327211649.3816010-1-dmatlack%40google.com?patch=12646
> >
> > Do you want to update the patch to use DECLARE_PCI_FIXUP_HEADER
> > instead of DECLARE_PCI_FIXUP_EARLY, as Sashiko suggested?
> >
> > I don't know the IOMMU init ordering with respect to PCI enumeration,
> > but header fixups are run in pci_device_add() before it calls
> > device_add().
> 
> Yes I would like to work on another version. I have 3 things I want to
> investigate/fix:
> 
>  * Fix the bug Sashiko found with early vs. header fixups.
>  * Investigate whether no_ats be a u8 instead of unsigned int to avoid
> increasing sizeof(struct pci_dev).
>  * Investigate Boalu's finding. Maybe this issue is specific to VF
> creation, and changing the order of calls there would be a better
> solution.

OK, I'll drop this one for now and watch for an update.