linux-kernel - Re: [PATCH v3 1/1] iommu: Allow attaching static domains in iommu_attach_device

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Message-ID: <c6f5e533-5e60-494c-93fd-5a004a9a13a0@linux.intel.com>
Date: Thu, 24 Apr 2025 14:54:43 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Vasant Hegde <vasant.hegde@....com>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Kevin Tian <kevin.tian@...el.com>, Jason Gunthorpe <jgg@...dia.com>,
 shangsong2@...ovo.com, Dave Jiang <dave.jiang@...el.com>
Cc: jack.vogel@...cle.com, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v3 1/1] iommu: Allow attaching static domains in
 iommu_attach_device_pasid()

On 4/24/25 14:49, Vasant Hegde wrote:
> On 4/24/2025 9:11 AM, Lu Baolu wrote:
>> The idxd driver attaches the default domain to a PASID of the device to
>> perform kernel DMA using that PASID. The domain is attached to the
>> device's PASID through iommu_attach_device_pasid(), which checks if the
>> domain->owner matches the iommu_ops retrieved from the device. If they
>> do not match, it returns a failure.
>>
>>          if (ops != domain->owner || pasid == IOMMU_NO_PASID)
>>                  return -EINVAL;
>>
>> The static identity domain implemented by the intel iommu driver doesn't
>> specify the domain owner. Therefore, kernel DMA with PASID doesn't work
>> for the idxd driver if the device translation mode is set to passthrough.
>>
>> Generally the owner field of static domains are not set because they are
>> already part of iommu ops. Add a helper domain_iommu_ops_compatible()
>> that checks if a domain is compatible with the device's iommu ops. This
>> helper explicitly allows the static blocked and identity domains associated
>> with the device's iommu_ops to be considered compatible.
>>
>> Fixes: 2031c469f816 ("iommu/vt-d: Add support for static identity domain")
>> Closes:https://bugzilla.kernel.org/show_bug.cgi?id=220031
>> Cc:stable@...r.kernel.org
>> Suggested-by: Jason Gunthorpe<jgg@...dia.com>
>> Link:https://lore.kernel.org/linux-iommu/20250422191554.GC1213339@ziepe.ca/
>> Signed-off-by: Lu Baolu<baolu.lu@...ux.intel.com>
>> Reviewed-by: Dave Jiang<dave.jiang@...el.com>
>> Reviewed-by: Robin Murphy<robin.murphy@....com>
> 
> Thanks! We have static identity domain in AMD driver as well. Some day we may
> hit similar issue 🙂
> 
> Patch looks good to me.
> 
> Reviewed-by: Vasant Hegde<vasant.hegde@....com>

Thank you!

> 
> W/ this change may be I should fix AMD driver like below. (No need to respin
> patch. I can send topup patch later).

I think that's a cleanup rather than a fix.

Thanks,
baolu