From: Jason Gunthorpe <jgg@nvidia.com>
To: Wei Wang <wei.w.wang@hotmail.com>
Cc: bhelgaas@google.com, akpm@linux-foundation.org, bp@alien8.de,
rdunlap@infradead.org, alex@shazbot.org, kevin.tian@intel.com,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH v1] PCI: Add support for ACS Enhanced Capability
Date: Thu, 22 Jan 2026 11:39:53 -0400 [thread overview]
Message-ID: <20260122153953.GP1134360@nvidia.com> (raw)
In-Reply-To: <SI2PR01MB4393709A1FFDD137DEBFA883DC96A@SI2PR01MB4393.apcprd01.prod.exchangelabs.com>
On Wed, Jan 21, 2026 at 05:18:46PM +0800, Wei Wang wrote:
> On 1/21/26 12:41 AM, Jason Gunthorpe wrote:
> > On Tue, Jan 20, 2026 at 02:11:30AM +0800, Wei Wang wrote:
> > > Add support for the ACS (Access Control Services) Enhanced Capability,
> > > introduced with PCIe Gen 5. These new configuration options can be
> > > controlled via the config_acs= boot parameter.
> > >
> > > By default, the ACS Unclaimed Request Redirect Control (URRC) bit is
> > > enabled if supported by the hardware (i.e., if the ACS Enhanced Capability
> > > is present). This setting is particularly important for device passthrough
> > > in virtualization scenarios.
> >
> > The memory target access bits should be set to request redirect as
> > well. Linux's grouping logic effectively has assumed the enabled behavior
> > forever.
> >
> Yes, sounds good, thanks.
> I think the REQ_ACS_FLAGS also needs to include the check.
That would make a mess, I think leave it alone. I tried to make some
patches for it once but it is going to be problematic..
Jason
next prev parent reply other threads:[~2026-01-22 15:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-19 18:11 [PATCH v1] PCI: Add support for ACS Enhanced Capability Wei Wang
2026-01-20 16:41 ` Jason Gunthorpe
2026-01-21 9:18 ` Wei Wang
2026-01-22 15:39 ` Jason Gunthorpe [this message]
2026-01-23 1:06 ` Wei Wang
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