linux-kernel - Re: [PATCH] iommu/amd: Enable PASID and ATS capabilities in the correct order

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Message-ID: <20250704125151.GL1209783@nvidia.com>
Date: Fri, 4 Jul 2025 09:51:51 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Easwar Hariharan <eahariha@...ux.microsoft.com>
Cc: Joerg Roedel <joro@...tes.org>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Vasant Hegde <vasant.hegde@....com>,
	Jerry Snitselaar <jsnitsel@...hat.com>,
	"open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux.dev>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iommu/amd: Enable PASID and ATS capabilities in the
 correct order

On Thu, Jul 03, 2025 at 08:54:33AM -0700, Easwar Hariharan wrote:
> Per the PCIe spec, behavior of the PASID capability is undefined if the
> value of the PASID Enable bit changes while the Enable bit of the
> function's ATS control register is Set. Unfortunately,
> pdev_enable_caps() does exactly that by ordering enabling ATS for the
> device before enabling PASID.
> 
> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> Cc: Vasant Hegde <vasant.hegde@....com>
> Cc: Jason Gunthorpe <jgg@...dia.com>
> Cc: Jerry Snitselaar <jsnitsel@...hat.com>
> Fixes: eda8c2860ab679 ("iommu/amd: Enable device ATS/PASID/PRI capabilities independently")
> Signed-off-by: Easwar Hariharan <eahariha@...ux.microsoft.com>
> ---
>  drivers/iommu/amd/iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

The other two drivers look like they do it Ok.

Jason