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

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Message-ID: <e8608bf9-45d6-4627-9a1a-88be0ff55cd3@linux.intel.com>
Date: Mon, 12 May 2025 10:43:24 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Wei Wang <wei.w.wang@...el.com>, dwmw2@...radead.org,
 kevin.tian@...el.com, yi.l.liu@...el.com, jroedel@...e.de,
 linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Subject: Re: [PATCH v1 3/3] iommu/vt-d: Fix ATS support check for integrated
 endpoints

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.

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