linux-kernel - RE: [PATCH v1 3/3] iommu/vt-d: Fix ATS support check for integrated endpoints

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Message-ID: <DS0PR11MB6373B31B77F9F6CDDFC9439FDC97A@DS0PR11MB6373.namprd11.prod.outlook.com>
Date: Mon, 12 May 2025 03:45:19 +0000
From: "Wang, Wei W" <wei.w.wang@...el.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>, "dwmw2@...radead.org"
	<dwmw2@...radead.org>, "Tian, Kevin" <kevin.tian@...el.com>, "Liu, Yi L"
	<yi.l.liu@...el.com>, "jroedel@...e.de" <jroedel@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: RE: [PATCH v1 3/3] iommu/vt-d: Fix ATS support check for integrated
 endpoints

On Monday, May 12, 2025 10:43 AM, Baolu Lu wrote:
> On 5/9/25 22:00, Wei Wang wrote:
> > The VT-d spec states that "SATC reporting structure identifies devices
> > that have address translation cache and that is validated per
> > requirements described in the 'Device TLB in System-on-Chip (SoC)
> Integrated Devices'
> 
> This is a spec recommendation for hardware implementation of the trusted
> ATS. I recommend supporting it alongside HPT support in the mainline kernel.

Sounds good, thanks.

> 
> This 1/3 and 2/3 look good to me. Thank you and I will queue them for next.
> 
> > section. It is recommended that system software enable ATC for this
> > device". It is possible for an integrated device to have PCI ATC
> > capability implemented but not validated per the requirements, and
> > thus not appear in the SATC structure as recommended for ATS enablement.
> >
> > The current implementation checks ATS support for integrated endpoints
> > in two places. First, it verifies if the integrated endpoint device is
> > listed in SATC. If not, it proceeds to the second check that always
> > returns true for integrated devices. This could result in endpoint
> > devices not recommended in SATC presenting "supported = true" to the
> caller.
> >
> > Add integrated_device_ats_supported() for the integrated device ATS
> > check in a single location, which improves readability. The above
> > issue is also fixed in the function via returning false in that case.
> >
> > Signed-off-by: Wei Wang<wei.w.wang@...el.com>
> > ---
> >   drivers/iommu/intel/iommu.c | 42 +++++++++++++++++++++++++------------
> >   1 file changed, 29 insertions(+), 13 deletions(-)
> 
> Thanks,
> baolu