Hi Bingbu,
Thanks for the update.
On Fri, Oct 25, 2024 at 01:52:31PM +0800, Bingbu Cao wrote:
> ipu6_mmu_map() operated on a per-page basis, it leads frequent
> spin_lock/unlock() and clflush_cache_range() for each page, it
> will cause inefficiencies especially when handling dma-bufs
> with large number of pages. However, the pages are likely concentrated
> pages by IOMMU DMA driver, IPU MMU driver can map the concentrated
> pages into less entries in l1 table.
>
> This change enhances ipu6_mmu_map() with batching process multiple
> contiguous pages. It significantly reduces calls for spin_lock/unlock
> and clflush_cache_range() and improve the performance.
>
> Signed-off-by: Bingbu Cao <bingbu.cao@xxxxxxxxx>
> Signed-off-by: Jianhui Dai <jianhui.j.dai@xxxxxxxxx>
> ---
> drivers/media/pci/intel/ipu6/ipu6-mmu.c | 144 +++++++++++++++-----------------
> 1 file changed, 69 insertions(+), 75 deletions(-)
>
> diff --git a/drivers/media/pci/intel/ipu6/ipu6-mmu.c b/drivers/media/pci/intel/ipu6/ipu6-mmu.c
> index 9ea6789bca5e..e957ccb4691d 100644
> --- a/drivers/media/pci/intel/ipu6/ipu6-mmu.c
> +++ b/drivers/media/pci/intel/ipu6/ipu6-mmu.c
> @@ -295,72 +295,90 @@ static size_t l2_unmap(struct ipu6_mmu_info *mmu_info, unsigned long iova,
> static int l2_map(struct ipu6_mmu_info *mmu_info, unsigned long iova,
> phys_addr_t paddr, size_t size)
> {
> - u32 l1_idx = iova >> ISP_L1PT_SHIFT;
> - u32 iova_start = iova;
> + struct device *dev = mmu_info->dev;
> + unsigned int l2_entries;
> u32 *l2_pt, *l2_virt;
> unsigned int l2_idx;
> unsigned long flags;
> + size_t mapped = 0;
> dma_addr_t dma;
> u32 l1_entry;
> -
> - dev_dbg(mmu_info->dev,
> - "mapping l2 page table for l1 index %u (iova %8.8x)\n",
> - l1_idx, (u32)iova);
> + u32 l1_idx;
> + int err = 0;
>
> spin_lock_irqsave(&mmu_info->lock, flags);
> - l1_entry = mmu_info->l1_pt[l1_idx];
> - if (l1_entry == mmu_info->dummy_l2_pteval) {
> - l2_virt = mmu_info->l2_pts[l1_idx];
> - if (likely(!l2_virt)) {
> - l2_virt = alloc_l2_pt(mmu_info);
> - if (!l2_virt) {
> - spin_unlock_irqrestore(&mmu_info->lock, flags);
> - return -ENOMEM;
> - }
> - }
> -
> - dma = map_single(mmu_info, l2_virt);
> - if (!dma) {
> - dev_err(mmu_info->dev, "Failed to map l2pt page\n");
> - free_page((unsigned long)l2_virt);
> - spin_unlock_irqrestore(&mmu_info->lock, flags);
> - return -EINVAL;
> - }
> -
> - l1_entry = dma >> ISP_PADDR_SHIFT;
> -
> - dev_dbg(mmu_info->dev, "page for l1_idx %u %p allocated\n",
> - l1_idx, l2_virt);
> - mmu_info->l1_pt[l1_idx] = l1_entry;
> - mmu_info->l2_pts[l1_idx] = l2_virt;
> - clflush_cache_range((void *)&mmu_info->l1_pt[l1_idx],
> - sizeof(mmu_info->l1_pt[l1_idx]));
> - }
> -
> - l2_pt = mmu_info->l2_pts[l1_idx];
> -
> - dev_dbg(mmu_info->dev, "l2_pt at %p with dma 0x%x\n", l2_pt, l1_entry);
>
> paddr = ALIGN(paddr, ISP_PAGE_SIZE);
> + for (l1_idx = iova >> ISP_L1PT_SHIFT;
> + size > 0 && l1_idx < ISP_L1PT_PTES; l1_idx++) {
> + dev_dbg(dev,
> + "mapping l2 page table for l1 index %u (iova %8.8x)\n",
> + l1_idx, (u32)iova);
>
> - l2_idx = (iova_start & ISP_L2PT_MASK) >> ISP_L2PT_SHIFT;
> + l1_entry = mmu_info->l1_pt[l1_idx];
> + if (l1_entry == mmu_info->dummy_l2_pteval) {
> + l2_virt = mmu_info->l2_pts[l1_idx];
> + if (likely(!l2_virt)) {
likely() should only be used if it's really, really uncommon on a hot path.
I don't think that's the case here.
Can it even happen l2_virt is NULL here? l1_entry has been assigned while
the l2 PT page has been mapped so both are either dummy / NULL or valid
values. The l2 pages aren't unmapped in unmap, but only in
ipu6_mmu_destroy(). Same goes for the map_single() if l2_virt was valid
already, the page has been mapped, too.
This seems like a pre-existing problem. If there is no actual bug here but
just inconsistent implementation (so it would seem), I think it's fine to
address this on top.
Can you conform this?
> + l2_virt = alloc_l2_pt(mmu_info);
> + if (!l2_virt) {
> + err = -ENOMEM;
> + goto error;
> + }
> + }
>
> - dev_dbg(mmu_info->dev, "l2_idx %u, phys 0x%8.8x\n", l2_idx,
> - l2_pt[l2_idx]);
> - if (l2_pt[l2_idx] != mmu_info->dummy_page_pteval) {
> - spin_unlock_irqrestore(&mmu_info->lock, flags);
> - return -EINVAL;
> + dma = map_single(mmu_info, l2_virt);
> + if (!dma) {
> + dev_err(dev, "Failed to map l2pt page\n");
> + free_page((unsigned long)l2_virt);
> + err = -EINVAL;
> + goto error;
> + }
> +
> + l1_entry = dma >> ISP_PADDR_SHIFT;
> +
> + dev_dbg(dev, "page for l1_idx %u %p allocated\n",
> + l1_idx, l2_virt);
> + mmu_info->l1_pt[l1_idx] = l1_entry;
> + mmu_info->l2_pts[l1_idx] = l2_virt;
> +
> + clflush_cache_range(&mmu_info->l1_pt[l1_idx],
> + sizeof(mmu_info->l1_pt[l1_idx]));
> + }
> +
> + l2_pt = mmu_info->l2_pts[l1_idx];
> + l2_entries = 0;
> +
> + for (l2_idx = (iova & ISP_L2PT_MASK) >> ISP_L2PT_SHIFT;
> + size > 0 && l2_idx < ISP_L2PT_PTES; l2_idx++) {
> + l2_pt[l2_idx] = paddr >> ISP_PADDR_SHIFT;
> +
> + dev_dbg(dev, "l2 index %u mapped as 0x%8.8x\n", l2_idx,
> + l2_pt[l2_idx]);
> +
> + iova += ISP_PAGE_SIZE;
> + paddr += ISP_PAGE_SIZE;
> + mapped += ISP_PAGE_SIZE;
> + size -= ISP_PAGE_SIZE;
> +
> + l2_entries++;
> + }
> +
> + WARN_ON_ONCE(!l2_entries);
> + clflush_cache_range(&l2_pt[l2_idx - l2_entries],
> + sizeof(l2_pt[0]) * l2_entries);
> }
>
> - l2_pt[l2_idx] = paddr >> ISP_PADDR_SHIFT;
> -
> - clflush_cache_range((void *)&l2_pt[l2_idx], sizeof(l2_pt[l2_idx]));
> spin_unlock_irqrestore(&mmu_info->lock, flags);
>
> - dev_dbg(mmu_info->dev, "l2 index %u mapped as 0x%8.8x\n", l2_idx,
> - l2_pt[l2_idx]);
> -
> return 0;
> +
> +error:
> + spin_unlock_irqrestore(&mmu_info->lock, flags);
> + /* unroll mapping in case something went wrong */
> + if (mapped)
> + l2_unmap(mmu_info, iova - mapped, paddr - mapped, mapped);
> +
> + return err;
> }
>
> static int __ipu6_mmu_map(struct ipu6_mmu_info *mmu_info, unsigned long iova,
> @@ -692,10 +710,7 @@ size_t ipu6_mmu_unmap(struct ipu6_mmu_info *mmu_info, unsigned long iova,
> int ipu6_mmu_map(struct ipu6_mmu_info *mmu_info, unsigned long iova,
> phys_addr_t paddr, size_t size)
> {
> - unsigned long orig_iova = iova;
> unsigned int min_pagesz;
> - size_t orig_size = size;
> - int ret = 0;
>
> if (mmu_info->pgsize_bitmap == 0UL)
> return -ENODEV;
> @@ -718,28 +733,7 @@ int ipu6_mmu_map(struct ipu6_mmu_info *mmu_info, unsigned long iova,
> dev_dbg(mmu_info->dev, "map: iova 0x%lx pa %pa size 0x%zx\n",
> iova, &paddr, size);
>
> - while (size) {
> - size_t pgsize = ipu6_mmu_pgsize(mmu_info->pgsize_bitmap,
> - iova | paddr, size);
> -
> - dev_dbg(mmu_info->dev,
> - "mapping: iova 0x%lx pa %pa pgsize 0x%zx\n",
> - iova, &paddr, pgsize);
> -
> - ret = __ipu6_mmu_map(mmu_info, iova, paddr, pgsize);
> - if (ret)
> - break;
> -
> - iova += pgsize;
> - paddr += pgsize;
> - size -= pgsize;
> - }
> -
> - /* unroll mapping in case something went wrong */
> - if (ret)
> - ipu6_mmu_unmap(mmu_info, orig_iova, orig_size - size);
> -
> - return ret;
> + return __ipu6_mmu_map(mmu_info, iova, paddr, size);
> }
>
> static void ipu6_mmu_destroy(struct ipu6_mmu *mmu)
--
Kind regards,
Sakari Ailus
