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SubjectRe: [PATCH v5 4/7] iommu/sva: Stop using ioasid_set for SVA
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On 3/10/23 6:21 AM, Jacob Pan wrote:
> From: Jason Gunthorpe <jgg@nvidia.com>
>
> Instead SVA drivers can use a simple global IDA to allocate PASIDs for
> each mm_struct.
>
> Future work would be to allow drivers using the SVA APIs to reserve global
> PASIDs from this IDA for their internal use, eg with the DMA API PASID
> support.
>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> v5:
> - Put removing iommu_sva_find() to a separate patch (Kevin)
> - Make pasid allocation range to be inclusive (Tina)
> - Simplified return code handling (Baolu)
> v4:
> - Keep GFP_ATOMIC flag for PASID allocation, will changed to
> GFP_KERNEL in a separate patch.
> ---
> drivers/iommu/iommu-sva.c | 42 +++++++++++++--------------------------
> drivers/iommu/iommu-sva.h | 2 --
> 2 files changed, 14 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index 4f357ef14f04..b75711bdbe97 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -9,47 +9,33 @@
> #include "iommu-sva.h"
>
> static DEFINE_MUTEX(iommu_sva_lock);
> -static DECLARE_IOASID_SET(iommu_sva_pasid);
> +static DEFINE_IDA(iommu_global_pasid_ida);
>
> -/**
> - * iommu_sva_alloc_pasid - Allocate a PASID for the mm
> - * @mm: the mm
> - * @min: minimum PASID value (inclusive)
> - * @max: maximum PASID value (inclusive)
> - *
> - * Try to allocate a PASID for this mm, or take a reference to the existing one
> - * provided it fits within the [@min, @max] range. On success the PASID is
> - * available in mm->pasid and will be available for the lifetime of the mm.
> - *
> - * Returns 0 on success and < 0 on error.
> - */
> -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, ioasid_t min, ioasid_t max)
> {
> int ret = 0;
> - ioasid_t pasid;
>
> - if (min == INVALID_IOASID || max == INVALID_IOASID ||
> - min == 0 || max < min)
> + if (!pasid_valid(min) || !pasid_valid(max) ||
> + min == 0 || max < min)

No need to change above line.

> return -EINVAL;
>
> mutex_lock(&iommu_sva_lock);
> /* Is a PASID already associated with this mm? */
> if (pasid_valid(mm->pasid)) {
> - if (mm->pasid < min || mm->pasid >= max)
> + if (mm->pasid < min || mm->pasid > max)

I forgot why do we need to change above line. But it's better to put
some comments there so that people don't need to dive into
ioasid_alloc() to know the inclusion or exclusion of @min or @max.

> ret = -EOVERFLOW;
> goto out;
> }
>
> - pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
> - if (!pasid_valid(pasid))
> - ret = -ENOMEM;
> - else
> - mm->pasid = pasid;
> + ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_ATOMIC);
> + if (ret < 0)
> + goto out;
> + mm->pasid = ret;
> + ret = 0;
> out:
> mutex_unlock(&iommu_sva_lock);
> return ret;
> }
> -EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);
>
> /**
> * iommu_sva_bind_device() - Bind a process address space to a device
> @@ -221,8 +207,8 @@ iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
>
> void mm_pasid_drop(struct mm_struct *mm)
> {
> - if (pasid_valid(mm->pasid)) {
> - ioasid_free(mm->pasid);
> - mm->pasid = INVALID_IOASID;
> - }
> + if (likely(!pasid_valid(mm->pasid)))
> + return;
> +
> + ida_free(&iommu_global_pasid_ida, mm->pasid);

Any reason why do you drop "mm->pasid = INVALID_IOASID;" here?

> }
> diff --git a/drivers/iommu/iommu-sva.h b/drivers/iommu/iommu-sva.h
> index 102eae1817a2..c22d0174ad61 100644
> --- a/drivers/iommu/iommu-sva.h
> +++ b/drivers/iommu/iommu-sva.h
> @@ -8,8 +8,6 @@
> #include <linux/ioasid.h>
> #include <linux/mm_types.h>
>
> -int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max);
> -
> /* I/O Page fault */
> struct device;
> struct iommu_fault;

Best regards,
baolu

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