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SubjectRe: [PATCH v6 2/4] iommu: Move global PASID allocation from SVA to core
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On 5/20/23 4:32 AM, Jacob Pan wrote:
> Global PASID can be used beyond SVA. For example, drivers that use
> Intel ENQCMD to submit work must use global PASIDs in that PASID
> is stored in a per CPU MSR. When such device need to submit work
> for in-kernel DMA with PASID, it must allocate PASIDs from the same
> global number space to avoid conflict.
>
> This patch moves global PASID allocation APIs from SVA to IOMMU APIs.
> Reserved PASIDs, currently only RID_PASID, are excluded from the global
> PASID allocation.
>
> It is expected that device drivers will use the allocated PASIDs to
> attach to appropriate IOMMU domains for use.
>
> Signed-off-by: Jacob Pan<jacob.jun.pan@linux.intel.com>
> ---
> v6: explicitly exclude reserved a range from SVA PASID allocation
> check mm PASID compatibility with device
> v5: move PASID range check inside API so that device drivers only pass
> in struct device* (Kevin)
> v4: move dummy functions outside ifdef CONFIG_IOMMU_SVA (Baolu)
> ---
> drivers/iommu/iommu-sva.c | 33 ++++++++++++++-------------------
> drivers/iommu/iommu.c | 24 ++++++++++++++++++++++++
> include/linux/iommu.h | 10 ++++++++++
> 3 files changed, 48 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index 9821bc44f5ac..7fe8e977d8eb 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -10,33 +10,33 @@
> #include "iommu-sva.h"
>
> static DEFINE_MUTEX(iommu_sva_lock);
> -static DEFINE_IDA(iommu_global_pasid_ida);
>
> /* Allocate a PASID for the mm within range (inclusive) */
> -static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
> +static int iommu_sva_alloc_pasid(struct mm_struct *mm, struct device *dev)
> {
> + ioasid_t pasid;
> int ret = 0;
>
> - if (min == IOMMU_PASID_INVALID ||
> - max == IOMMU_PASID_INVALID ||
> - min == 0 || max < min)
> - return -EINVAL;
> -
> if (!arch_pgtable_dma_compat(mm))
> return -EBUSY;
>
> mutex_lock(&iommu_sva_lock);
> /* Is a PASID already associated with this mm? */
> if (mm_valid_pasid(mm)) {
> - if (mm->pasid < min || mm->pasid > max)
> - ret = -EOVERFLOW;
> + if (mm->pasid <= dev->iommu->max_pasids)
> + goto out;
> + dev_err(dev, "current mm PASID %d exceeds device range %d!",
> + mm->pasid, dev->iommu->max_pasids);
> + ret = -ERANGE;
> goto out;
> }

Nit: Above is just refactoring, so it's better to keep the code behavior
consistent. For example, no need to change the error# from -EOVERFLOW to
-ERANGE, and no need to leave a new kernel message.

Anyway, if you think these changes are helpful, it's better to have them
in separated patches.

In the end, perhaps we can simply have code like this:

if (mm_valid_pasid(mm)) {
if (mm->pasid > dev->iommu->max_pasids)
ret = -EOVERFLOW;
goto out;
}

Others look good to me, with above addressed,

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu

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