Re: [PATCH 3/4] iommu/arm-smmu-v3: Use pci_ats_supported()

Will Deacon
2020-05-18T15:37:43Z

On Fri, May 15, 2020 at 12:44:01PM +0200, Jean-Philippe Brucker wrote:
> The new pci_ats_supported() function checks if a device supports ATS and
> is allowed to use it.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
> I dropped the Ack because I slightly changed the patch to keep the
> fwspec check, since last version:
> https://lore.kernel.org/linux-iommu/20200311124506.208376-8-jean-philippe@linaro.org/
> ---
> drivers/iommu/arm-smmu-v3.c | 20 +++++---------------
> 1 file changed, 5 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 82508730feb7a1..39b935e86ab203 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -2652,26 +2652,16 @@ static void arm_smmu_install_ste_for_dev(struct arm_smmu_master *master)
> }
> }
>
> -#ifdef CONFIG_PCI_ATS
> static bool arm_smmu_ats_supported(struct arm_smmu_master *master)
> {
> - struct pci_dev *pdev;
> + struct device *dev = master->dev;
> struct arm_smmu_device *smmu = master->smmu;
> - struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(master->dev);
> -
> - if (!(smmu->features & ARM_SMMU_FEAT_ATS) || !dev_is_pci(master->dev) ||
> - !(fwspec->flags & IOMMU_FWSPEC_PCI_RC_ATS) || pci_ats_disabled())
> - return false;
> + struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>
> - pdev = to_pci_dev(master->dev);
> - return !pdev->untrusted && pdev->ats_cap;
> + return (smmu->features & ARM_SMMU_FEAT_ATS) &&
> + !(fwspec->flags & IOMMU_FWSPEC_PCI_RC_ATS) &&
> + dev_is_pci(dev) && pci_ats_supported(to_pci_dev(dev));

nit, but I think this is clearer if you leave it split up (untested diff
below).

Will

--->8

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 82508730feb7..c5730557dbe3 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2652,26 +2652,20 @@ static void arm_smmu_install_ste_for_dev(struct arm_smmu_master *master)
}
}

-#ifdef CONFIG_PCI_ATS
static bool arm_smmu_ats_supported(struct arm_smmu_master *master)
{
- struct pci_dev *pdev;
+ struct device *dev = master->dev;
struct arm_smmu_device *smmu = master->smmu;
- struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(master->dev);
+ struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);

- if (!(smmu->features & ARM_SMMU_FEAT_ATS) || !dev_is_pci(master->dev) ||
- !(fwspec->flags & IOMMU_FWSPEC_PCI_RC_ATS) || pci_ats_disabled())
+ if (!(smmu->features & ARM_SMMU_FEAT_ATS))
return false;

- pdev = to_pci_dev(master->dev);
- return !pdev->untrusted && pdev->ats_cap;
-}
-#else
-static bool arm_smmu_ats_supported(struct arm_smmu_master *master)
-{
- return false;
+ if (!(fwspec->flags & IOMMU_FWSPEC_PCI_RC_ATS))
+ return false;
+
+ return dev_is_pci(dev) && pci_ats_supported(to_pci_dev(dev));
}
-#endif

static void arm_smmu_enable_ats(struct arm_smmu_master *master)
{