On 5/7/25 06:59, Yi Liu wrote:

On 2025/5/6 05:15, Tushar Dave wrote:

...

Generally PASID support requires ACS settings that usually create single device groups, but there are some niche cases where we can get multi-device groups and still have working PASID support. The primary issue is that PCI switches are not required to treat PASID tagged TLPs specially so appropriate ACS settings are required to route all TLPs to the host bridge if PASID is going to work properly.

pci_enable_pasid() does check that each device that will use PASID has the proper ACS settings to achieve this routing.

However, no-PASID devices can be combined with PASID capable devices within the same topology using non-uniform ACS settings. In this case the no-PASID devices may not have strict route to host ACS flags and end up being grouped with the PASID devices.

This configuration fails to allow use of the PASID within the iommu core code which wrongly checks if the no-PASID device supports PASID.

Fix this by ignoring no-PASID devices during the PASID validation. They will never issue a PASID TLP anyhow so they can be ignored.

Fixes: c404f55c26fc ("iommu: Validate the PASID in iommu_attach_device_pasid()") Cc: stable@vger.kernel.org Signed-off-by: Tushar Dave tdave@nvidia.com

---

changes in v3:

• addressed review comment from Vasant.

drivers/iommu/iommu.c | 27 +++++++++++++++++++--------   1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 60aed01e54f2..636fc68a8ec0 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -3329,10 +3329,12 @@ static int __iommu_set_group_pasid(struct iommu_domain *domain,       int ret;       for_each_group_device(group, device) { -        ret = domain->ops->set_dev_pasid(domain, device->dev, -                         pasid, NULL); -        if (ret) -            goto err_revert; +        if (device->dev->iommu->max_pasids > 0) { +            ret = domain->ops->set_dev_pasid(domain, device->dev, +                             pasid, NULL); +            if (ret) +                goto err_revert; +        }       }       return 0; @@ -3342,7 +3344,8 @@ static int __iommu_set_group_pasid(struct iommu_domain *domain,       for_each_group_device(group, device) {           if (device == last_gdev)               break; -        iommu_remove_dev_pasid(device->dev, pasid, domain); +        if (device->dev->iommu->max_pasids > 0) +            iommu_remove_dev_pasid(device->dev, pasid, domain);

Reviewed-by: Yi Liu yi.l.liu@intel.com

with a nit. would it save some loc by adding the max_pasids check in iommu_remove_dev_pasid()?

With current code:

drivers/iommu/iommu.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-)

If I move the pasid check in iommu_remove_dev_pasid(), it would be:

drivers/iommu/iommu.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-)

e.g.

@@ -3318,8 +3318,9 @@ static void iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid, const struct iommu_ops *ops = dev_iommu_ops(dev); struct iommu_domain *blocked_domain = ops->blocked_domain;

- WARN_ON(blocked_domain->ops->set_dev_pasid(blocked_domain, - dev, pasid, domain)); + if (dev->iommu->max_pasids > 0) + WARN_ON(blocked_domain->ops->set_dev_pasid(blocked_domain, + dev, pasid, domain)); }

static int __iommu_set_group_pasid(struct iommu_domain *domain, @@ -3329,10 +3330,12 @@ static int __iommu_set_group_pasid(struct iommu_domain *domain, int ret;

for_each_group_device(group, device) { - ret = domain->ops->set_dev_pasid(domain, device->dev, - pasid, NULL); - if (ret) - goto err_revert; + if (device->dev->iommu->max_pasids > 0) { + ret = domain->ops->set_dev_pasid(domain, device->dev, + pasid, NULL); + if (ret) + goto err_revert; + } }

return 0;

Last hunk remain same as before for iommu_attach_device_pasid()

Let me know.

-Tushar

...

}       return ret;   } @@ -3353,8 +3356,10 @@ static void __iommu_remove_group_pasid(struct iommu_group *group,   {       struct group_device *device; -    for_each_group_device(group, device) -        iommu_remove_dev_pasid(device->dev, pasid, domain); +    for_each_group_device(group, device) { +        if (device->dev->iommu->max_pasids > 0) +            iommu_remove_dev_pasid(device->dev, pasid, domain); +    }   }   /* @@ -3391,7 +3396,13 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,       mutex_lock(&group->mutex);       for_each_group_device(group, device) { -        if (pasid >= device->dev->iommu->max_pasids) { +        /* +         * Skip PASID validation for devices without PASID support +         * (max_pasids = 0). These devices cannot issue transactions +         * with PASID, so they don't affect group's PASID usage. +         */ +        if ((device->dev->iommu->max_pasids > 0) && +            (pasid >= device->dev->iommu->max_pasids)) {               ret = -EINVAL;               goto out_unlock;           }