Re: [Freedreno] [PATCH v2] drm/msm/iommu: optimize map/unmap
On Tue, Aug 23, 2022 at 2:37 PM Akhil P Oommen wrote:
>
> On 8/23/2022 10:07 PM, Rob Clark wrote:
> > From: Rob Clark
> >
> > Using map_pages/unmap_pages cuts down on the # of pgtable walks needed
> > in the process of finding where to insert/remove an entry. The end
> > result is ~5-10x faster than mapping a single page at a time.
> >
> > v2: Rename iommu_pgsize(), drop obsolete comments, fix error handling
> > in msm_iommu_pagetable_map()
> >
> > Signed-off-by: Rob Clark
> > ---
> > drivers/gpu/drm/msm/msm_iommu.c | 101 +++-
> > 1 file changed, 86 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_iommu.c
> > b/drivers/gpu/drm/msm/msm_iommu.c
> > index a54ed354578b..5577cea7c009 100644
> > --- a/drivers/gpu/drm/msm/msm_iommu.c
> > +++ b/drivers/gpu/drm/msm/msm_iommu.c
> > @@ -21,6 +21,7 @@ struct msm_iommu_pagetable {
> > struct msm_mmu base;
> > struct msm_mmu *parent;
> > struct io_pgtable_ops *pgtbl_ops;
> > + unsigned long pgsize_bitmap;/* Bitmap of page sizes in use */
> > phys_addr_t ttbr;
> > u32 asid;
> > };
> > @@ -29,23 +30,84 @@ static struct msm_iommu_pagetable *to_pagetable(struct
> > msm_mmu *mmu)
> > return container_of(mmu, struct msm_iommu_pagetable, base);
> > }
> >
> > +/* based on iommu_pgsize() in iommu.c: */
> > +static size_t calc_pgsize(struct msm_iommu_pagetable *pagetable,
> > +unsigned long iova, phys_addr_t paddr,
> > +size_t size, size_t *count)
> > +{
> > + unsigned int pgsize_idx, pgsize_idx_next;
> > + unsigned long pgsizes;
> > + size_t offset, pgsize, pgsize_next;
> > + unsigned long addr_merge = paddr | iova;
> > +
> > + /* Page sizes supported by the hardware and small enough for @size */
> > + pgsizes = pagetable->pgsize_bitmap & GENMASK(__fls(size), 0);
> > +
> > + /* Constrain the page sizes further based on the maximum alignment */
> > + if (likely(addr_merge))
> > + pgsizes &= GENMASK(__ffs(addr_merge), 0);
> > +
> > + /* Make sure we have at least one suitable page size */
> > + BUG_ON(!pgsizes);
> > +
> > + /* Pick the biggest page size remaining */
> > + pgsize_idx = __fls(pgsizes);
> > + pgsize = BIT(pgsize_idx);
> > + if (!count)
> > + return pgsize;
> > +
> > + /* Find the next biggest support page size, if it exists */
> > + pgsizes = pagetable->pgsize_bitmap & ~GENMASK(pgsize_idx, 0);
> > + if (!pgsizes)
> > + goto out_set_count;
> > +
> > + pgsize_idx_next = __ffs(pgsizes);
> > + pgsize_next = BIT(pgsize_idx_next);
> > +
> > + /*
> > + * There's no point trying a bigger page size unless the virtual
> > + * and physical addresses are similarly offset within the larger page.
> > + */
> > + if ((iova ^ paddr) & (pgsize_next - 1))
> > + goto out_set_count;
> > +
> > + /* Calculate the offset to the next page size alignment boundary */
> > + offset = pgsize_next - (addr_merge & (pgsize_next - 1));
> > +
> > + /*
> > + * If size is big enough to accommodate the larger page, reduce
> > + * the number of smaller pages.
> > + */
> > + if (offset + pgsize_next <= size)
> > + size = offset;
> > +
> > +out_set_count:
> > + *count = size >> pgsize_idx;
> > + return pgsize;
> > +}
> > +
> Can we keep this in iommu driver? Seems useful to other drivers too.
This might end up being only temporary.. Robin had the idea of adding
a private way to create "dummy" iommu_domain's which we could use
instead of the pgtbl ops directly. On one hand, it would simplify
this quite a bit. On the other hand it would force powering up (at
least the SMMU) for unmaps/maps, and make it harder to do things like
this:
https://patchwork.freedesktop.org/patch/498660/?series=107536=1
> Perhaps implement an sg friendly version of iopgtble ops, like
> unmap_sg() maybe!
Probably not a good idea to push more into the iopgtbl
implementations.. __iommu_map_sg() does have a bit of cleverness, but
that shouldn't really be required if we get our sg from
drm_prime_pages_to_sg() since sg_alloc_append_table_from_pages()
already performs a similar merging
BR,
-R
>
> -Akhil.
> > static int msm_iommu_pagetable_unmap(struct msm_mmu *mmu, u64 iova,
> > size_t size)
> > {
> > struct msm_iommu_pagetable *pagetable = to_pagetable(mmu);
> > struct io_pgtable_ops *ops = pagetable->pgtbl_ops;
> > - size_t unmapped = 0;
> >
> > - /* Unmap the block one page at a time */
> > while (size) {
> > - unmapped += ops->unmap(ops, iova, 4096, NULL);
> > - iova += 4096;
> > - size -= 4096;
> > + size_t unmapped, pgsize, count;
> > +
> > + pgsize = calc_pgsize(pagetable, iova, iova, size, );
> > +
> > + unmapped = ops->unmap_pages(ops, iova, pgsize,
Re: [Freedreno] [PATCH v2] drm/msm/iommu: optimize map/unmap
On 8/23/2022 10:07 PM, Rob Clark wrote:
From: Rob Clark
Using map_pages/unmap_pages cuts down on the # of pgtable walks needed
in the process of finding where to insert/remove an entry. The end
result is ~5-10x faster than mapping a single page at a time.
v2: Rename iommu_pgsize(), drop obsolete comments, fix error handling
in msm_iommu_pagetable_map()
Signed-off-by: Rob Clark
---
drivers/gpu/drm/msm/msm_iommu.c | 101 +++-
1 file changed, 86 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index a54ed354578b..5577cea7c009 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -21,6 +21,7 @@ struct msm_iommu_pagetable {
struct msm_mmu base;
struct msm_mmu *parent;
struct io_pgtable_ops *pgtbl_ops;
+ unsigned long pgsize_bitmap;/* Bitmap of page sizes in use */
phys_addr_t ttbr;
u32 asid;
};
@@ -29,23 +30,84 @@ static struct msm_iommu_pagetable *to_pagetable(struct
msm_mmu *mmu)
return container_of(mmu, struct msm_iommu_pagetable, base);
}
+/* based on iommu_pgsize() in iommu.c: */
+static size_t calc_pgsize(struct msm_iommu_pagetable *pagetable,
+ unsigned long iova, phys_addr_t paddr,
+ size_t size, size_t *count)
+{
+ unsigned int pgsize_idx, pgsize_idx_next;
+ unsigned long pgsizes;
+ size_t offset, pgsize, pgsize_next;
+ unsigned long addr_merge = paddr | iova;
+
+ /* Page sizes supported by the hardware and small enough for @size */
+ pgsizes = pagetable->pgsize_bitmap & GENMASK(__fls(size), 0);
+
+ /* Constrain the page sizes further based on the maximum alignment */
+ if (likely(addr_merge))
+ pgsizes &= GENMASK(__ffs(addr_merge), 0);
+
+ /* Make sure we have at least one suitable page size */
+ BUG_ON(!pgsizes);
+
+ /* Pick the biggest page size remaining */
+ pgsize_idx = __fls(pgsizes);
+ pgsize = BIT(pgsize_idx);
+ if (!count)
+ return pgsize;
+
+ /* Find the next biggest support page size, if it exists */
+ pgsizes = pagetable->pgsize_bitmap & ~GENMASK(pgsize_idx, 0);
+ if (!pgsizes)
+ goto out_set_count;
+
+ pgsize_idx_next = __ffs(pgsizes);
+ pgsize_next = BIT(pgsize_idx_next);
+
+ /*
+* There's no point trying a bigger page size unless the virtual
+* and physical addresses are similarly offset within the larger page.
+*/
+ if ((iova ^ paddr) & (pgsize_next - 1))
+ goto out_set_count;
+
+ /* Calculate the offset to the next page size alignment boundary */
+ offset = pgsize_next - (addr_merge & (pgsize_next - 1));
+
+ /*
+* If size is big enough to accommodate the larger page, reduce
+* the number of smaller pages.
+*/
+ if (offset + pgsize_next <= size)
+ size = offset;
+
+out_set_count:
+ *count = size >> pgsize_idx;
+ return pgsize;
+}
+
Can we keep this in iommu driver? Seems useful to other drivers too.
Perhaps implement an sg friendly version of iopgtble ops, like
unmap_sg() maybe!
-Akhil.
static int msm_iommu_pagetable_unmap(struct msm_mmu *mmu, u64 iova,
size_t size)
{
struct msm_iommu_pagetable *pagetable = to_pagetable(mmu);
struct io_pgtable_ops *ops = pagetable->pgtbl_ops;
- size_t unmapped = 0;
- /* Unmap the block one page at a time */
while (size) {
- unmapped += ops->unmap(ops, iova, 4096, NULL);
- iova += 4096;
- size -= 4096;
+ size_t unmapped, pgsize, count;
+
+ pgsize = calc_pgsize(pagetable, iova, iova, size, );
+
+ unmapped = ops->unmap_pages(ops, iova, pgsize, count, NULL);
+ if (!unmapped)
+ break;
+
+ iova += unmapped;
+ size -= unmapped;
}
iommu_flush_iotlb_all(to_msm_iommu(pagetable->parent)->domain);
- return (unmapped == size) ? 0 : -EINVAL;
+ return (size == 0) ? 0 : -EINVAL;
}
static int msm_iommu_pagetable_map(struct msm_mmu *mmu, u64 iova,
@@ -54,7 +116,6 @@ static int msm_iommu_pagetable_map(struct msm_mmu *mmu, u64
iova,
struct msm_iommu_pagetable *pagetable = to_pagetable(mmu);
struct io_pgtable_ops *ops = pagetable->pgtbl_ops;
struct scatterlist *sg;
- size_t mapped = 0;
u64 addr = iova;
unsigned int i;
@@ -62,17 +123,26 @@ static int msm_iommu_pagetable_map(struct msm_mmu *mmu, u64 iova,
size_t size = sg->length;
phys_addr_t phys = sg_phys(sg);
- /* Map the block one page at a time */
while (size) {
- if (ops->map(ops, addr, phys, 4096, prot, GFP_KERNEL)) {
-
