linux-kernel - Re: [PATCH] iommu/intel: Enable pci capabilities before assigning cache tags

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Date: Wed, 26 Jun 2024 09:09:04 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: j.granados@...sung.com, David Woodhouse <dwmw2@...radead.org>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>
Cc: baolu.lu@...ux.intel.com, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/intel: Enable pci capabilities before assigning
 cache tags

On 6/25/24 9:49 PM, Joel Granados via B4 Relay wrote:
> From: Joel Granados<j.granados@...sung.com>
> 
> Enable the pci capabilities by calling iommu_enable_pci_caps before we
> assign a cache tag. The cache_tag_assign_domain call in
> dmar_domain_attach_device uses the device_domain_info->ats_enabled
> element to decide on the cache_tag_type value. Therefore ats_enabled
> needs to be evaluated before the call to the tag cache assignment.
> 
> Signed-off-by: Joel Granados<j.granados@...sung.com>
> ---
> The "what" and "why" are included in the commit message.
> 
> Tried to place cache_tag_assign_domain before the early return in
> "if(dev_is_real_dma_subdevice(dev))". This means that the call to
> iommu_enable_pci_caps landed before the setup functions [1] which is not
> an issue as they seem to be orthogonal (I would like to be proven wrong
> here).
> 
> An alternative to this patch would be to use a different way of checking
> if the device is ATS enabled in __cache_tag_assign_domain.
> 
> Comments greatly appreciated

Thank you very much for the patch. But we already have a similar patch
which has been picked by Joerg for 6.10-rc.

https://lore.kernel.org/linux-iommu/20240620062940.201786-1-baolu.lu@linux.intel.com/

Can you please check whether above patch works for you?

Best regards,
baolu