Re: [PATCH v2 1/1] iommu/vt-d: Fix missed device TLB cache tag

Joel Granados
2024-06-27T11:27:43Z

On Thu, Jun 20, 2024 at 02:29:40PM +0800, Lu Baolu wrote:
> When a domain is attached to a device, the required cache tags are
> assigned to the domain so that the related caches can be flushed
> whenever it is needed. The device TLB cache tag is created based
> on whether the ats_enabled field of the device's iommu data is set.
> This creates an ordered dependency between cache tag assignment and
> ATS enabling.
>
> The device TLB cache tag would not be created if device's ATS is
> enabled after the cache tag assignment. This causes devices with PCI
> ATS support to malfunction.
>
> The ATS control is exclusively owned by the iommu driver. Hence, move
> cache_tag_assign_domain() after PCI ATS enabling to make sure that the
> device TLB cache tag is created for the domain.
>
> Fixes: 3b1d9e2b2d68 ("iommu/vt-d: Add cache tag assignment interface")
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/intel/iommu.c | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> Change log:
> v2:
> - Reverting the order instead of adding unnecessary run-time overhead.
>
> v1:
> - https://lore.kernel.org/linux-iommu/20240619015345.182773-1-baolu.lu@linux.intel.com/
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 2e9811bf2a4e..fd11a080380c 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2114,12 +2114,6 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
> if (ret)
> return ret;
>
> - ret = cache_tag_assign_domain(domain, dev, IOMMU_NO_PASID);
> - if (ret) {
> - domain_detach_iommu(domain, iommu);
> - return ret;
> - }
> -
> info->domain = domain;
> spin_lock_irqsave(&domain->lock, flags);
> list_add(&info->link, &domain->devices);
> @@ -2137,15 +2131,21 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
> else
> ret = intel_pasid_setup_second_level(iommu, domain, dev, IOMMU_NO_PASID);
>
> - if (ret) {
> - device_block_translation(dev);
> - return ret;
> - }
> + if (ret)
> + goto out_block_translation;
>
> if (sm_supported(info->iommu) || !domain_type_is_si(info->domain))
> iommu_enable_pci_caps(info);
>
> + ret = cache_tag_assign_domain(domain, dev, IOMMU_NO_PASID);
> + if (ret)
> + goto out_block_translation;
> +
> return 0;
> +
> +out_block_translation:
> + device_block_translation(dev);
> + return ret;
> }
>
> /**
> --
> 2.34.1
>

Even though this has already been applied, its good to know that it
works :)

Tested-by: Joel Granados <j.granados@samsung.com>

--

Joel Granados