On Wed, 2014-02-12 at 14:28 -0800, Ben Widawsky wrote:
> Create 3 clear stages in PPGTT init. This will help with upcoming
> changes be more readable. The 3 stages are, allocation, dma mapping, and
> writing the P[DT]Es
>
> One nice benefit to the patches is that it makes 2 very clear error
> points, allocation, and mapping, and avoids having to do any handling
> after writing PTEs (something which was likely buggy before). This
> simplified error handling I suspect will be helpful when we move to
> deferred/dynamic page table allocation and mapping.
>
> The patches also attempts to break up some of the steps into more
> logical reviewable chunks, particularly when we free.
>
> v2: Don't call cleanup on the error path since that takes down the
> drm_mm and list entry, which aren't setup at this point.
>
> Signed-off-by: Ben Widawsky <b...@bwidawsk.net>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 2 +-
> drivers/gpu/drm/i915/i915_gem_gtt.c | 124
> +++++++++++++++++++++---------------
> 2 files changed, 73 insertions(+), 53 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 2572a95..cecbb9a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -709,7 +709,7 @@ struct i915_hw_ppgtt {
> };
> union {
> dma_addr_t *pt_dma_addr;
> - dma_addr_t *gen8_pt_dma_addr[4];
> + dma_addr_t **gen8_pt_dma_addr;
If there isn't any reason to allocate this dynamically I'd just leave
the static array. This would make the error path a bit simpler and be
more symmetric wrt. pd_dma_addr which is also a static array.
> };
>
> int (*enable)(struct i915_hw_ppgtt *ppgtt);
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c
> b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index ee38faf..c6c221c 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -326,12 +326,14 @@ static void gen8_ppgtt_free(struct i915_hw_ppgtt *ppgtt)
> for (i = 0; i < ppgtt->num_pd_pages ; i++)
> kfree(ppgtt->gen8_pt_dma_addr[i]);
>
> + kfree(ppgtt->gen8_pt_dma_addr);
> __free_pages(ppgtt->gen8_pt_pages, get_order(ppgtt->num_pt_pages <<
> PAGE_SHIFT));
> __free_pages(ppgtt->pd_pages, get_order(ppgtt->num_pd_pages <<
> PAGE_SHIFT));
> }
>
> static void gen8_ppgtt_unmap_pages(struct i915_hw_ppgtt *ppgtt)
> {
> + struct pci_dev *hwdev = ppgtt->base.dev->pdev;
> int i, j;
>
> for (i = 0; i < ppgtt->num_pd_pages; i++) {
> @@ -340,18 +342,14 @@ static void gen8_ppgtt_unmap_pages(struct i915_hw_ppgtt
> *ppgtt)
> if (!ppgtt->pd_dma_addr[i])
> continue;
>
> - pci_unmap_page(ppgtt->base.dev->pdev,
> - ppgtt->pd_dma_addr[i],
> - PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
> + pci_unmap_page(hwdev, ppgtt->pd_dma_addr[i], PAGE_SIZE,
> + PCI_DMA_BIDIRECTIONAL);
>
> for (j = 0; j < GEN8_PDES_PER_PAGE; j++) {
> dma_addr_t addr = ppgtt->gen8_pt_dma_addr[i][j];
> if (addr)
> - pci_unmap_page(ppgtt->base.dev->pdev,
> - addr,
> - PAGE_SIZE,
> - PCI_DMA_BIDIRECTIONAL);
> -
> + pci_unmap_page(hwdev, addr, PAGE_SIZE,
> + PCI_DMA_BIDIRECTIONAL);
> }
> }
> }
> @@ -369,27 +367,26 @@ static void gen8_ppgtt_cleanup(struct
> i915_address_space *vm)
> }
>
> /**
> - * GEN8 legacy ppgtt programming is accomplished through 4 PDP registers
> with a
> - * net effect resembling a 2-level page table in normal x86 terms. Each PDP
> - * represents 1GB of memory
> - * 4 * 512 * 512 * 4096 = 4GB legacy 32b address space.
> + * GEN8 legacy ppgtt programming is accomplished through a max 4 PDP
> registers
> + * with a net effect resembling a 2-level page table in normal x86 terms.
> Each
> + * PDP represents 1GB of memory 4 * 512 * 512 * 4096 = 4GB legacy 32b address
> + * space.
> *
> + * FIXME: split allocation into smaller pieces. For now we only ever do this
> + * once, but with full PPGTT, the multiple contiguous allocations will be
> bad.
> * TODO: Do something with the size parameter
> - **/
> + */
> static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt, uint64_t size)
> {
> struct page *pt_pages;
> - int i, j, ret = -ENOMEM;
> const int max_pdp = DIV_ROUND_UP(size, 1 << 30);
> const int num_pt_pages = GEN8_PDES_PER_PAGE * max_pdp;
> + int i, j, ret;
>
> if (size % (1<<30))
> DRM_INFO("Pages will be wasted unless GTT size (%llu) is
> divisible by 1GB\n", size);
>
> - /* FIXME: split allocation into smaller pieces. For now we only ever do
> - * this once, but with full PPGTT, the multiple contiguous allocations
> - * will be bad.
> - */
> + /* 1. Do all our allocations for page directories and page tables */
> ppgtt->pd_pages = alloc_pages(GFP_KERNEL, get_order(max_pdp <<
> PAGE_SHIFT));
> if (!ppgtt->pd_pages)
> return -ENOMEM;
> @@ -404,52 +401,66 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt,
> uint64_t size)
> ppgtt->num_pd_pages = 1 << get_order(max_pdp << PAGE_SHIFT);
> ppgtt->num_pt_pages = 1 << get_order(num_pt_pages << PAGE_SHIFT);
> ppgtt->num_pd_entries = max_pdp * GEN8_PDES_PER_PAGE;
> - ppgtt->enable = gen8_ppgtt_enable;
> - ppgtt->switch_mm = gen8_mm_switch;
> - ppgtt->base.clear_range = gen8_ppgtt_clear_range;
> - ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
> - ppgtt->base.cleanup = gen8_ppgtt_cleanup;
> - ppgtt->base.start = 0;
> - ppgtt->base.total = ppgtt->num_pt_pages * GEN8_PTES_PER_PAGE *
> PAGE_SIZE;
> -
> BUG_ON(ppgtt->num_pd_pages > GEN8_LEGACY_PDPS);
>
> + ppgtt->gen8_pt_dma_addr = kcalloc(max_pdp,
> + sizeof(*ppgtt->gen8_pt_dma_addr),
> + GFP_KERNEL);
> + if (!ppgtt->gen8_pt_dma_addr) {
> + ret = -ENOMEM;
> + goto bail;
On the error path, in gen8_ppgtt_free() we'd dereference the above NULL
ptr.
> + }
> +
> + for (i = 0; i < max_pdp; i++) {
> + ppgtt->gen8_pt_dma_addr[i] = kcalloc(GEN8_PDES_PER_PAGE,
> + sizeof(dma_addr_t),
> + GFP_KERNEL);
> + if (!ppgtt->gen8_pt_dma_addr[i]) {
> + ret = -ENOMEM;
> + goto bail;
> + }
> + }
> +
> /*
> - * - Create a mapping for the page directories.
> - * - For each page directory:
> - * allocate space for page table mappings.
> - * map each page table
> + * 2. Create all the DMA mappings for the page directories and page
> + * tables
> */
> for (i = 0; i < max_pdp; i++) {
> - dma_addr_t temp;
> - temp = pci_map_page(ppgtt->base.dev->pdev,
> - &ppgtt->pd_pages[i], 0,
> - PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
> - if (pci_dma_mapping_error(ppgtt->base.dev->pdev, temp))
> - goto err_out;
> -
> - ppgtt->pd_dma_addr[i] = temp;
> -
> - ppgtt->gen8_pt_dma_addr[i] = kmalloc(sizeof(dma_addr_t) *
> GEN8_PDES_PER_PAGE, GFP_KERNEL);
> - if (!ppgtt->gen8_pt_dma_addr[i])
> - goto err_out;
> + dma_addr_t pd_addr, pt_addr;
>
> + /* Get the page table mappings per page directory */
> for (j = 0; j < GEN8_PDES_PER_PAGE; j++) {
> struct page *p = &pt_pages[i * GEN8_PDES_PER_PAGE + j];
> - temp = pci_map_page(ppgtt->base.dev->pdev,
> - p, 0, PAGE_SIZE,
> - PCI_DMA_BIDIRECTIONAL);
>
> - if (pci_dma_mapping_error(ppgtt->base.dev->pdev, temp))
> - goto err_out;
> + pt_addr = pci_map_page(ppgtt->base.dev->pdev,
> + p, 0, PAGE_SIZE,
> + PCI_DMA_BIDIRECTIONAL);
> + ret = pci_dma_mapping_error(ppgtt->base.dev->pdev,
> pt_addr);
> + if (ret)
> + goto bail;
>
> - ppgtt->gen8_pt_dma_addr[i][j] = temp;
> + ppgtt->gen8_pt_dma_addr[i][j] = pt_addr;
> }
> +
> + /* And the page directory mappings */
> + pd_addr = pci_map_page(ppgtt->base.dev->pdev,
> + &ppgtt->pd_pages[i], 0,
> + PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
> + ret = pci_dma_mapping_error(ppgtt->base.dev->pdev, pd_addr);
> + if (ret)
> + goto bail;
The error path here would leak the above page table mappings, since
ppgtt->pd_dma_addr[i] is still zero, but in gen8_ppgtt_unmap_pages() we
do a if (!ppgtt->pd_dma_addr[i]) continue; skipping the page table unmap
part. This is reworked in your later patches, but the issue is still
there in the final version.
> +
> + ppgtt->pd_dma_addr[i] = pd_addr;
> }
>
> - /* For now, the PPGTT helper functions all require that the PDEs are
> + /*
> + * 3. Map all the page directory entires to point to the page tables
> + * we've allocated.
> + *
> + * For now, the PPGTT helper functions all require that the PDEs are
> * plugged in correctly. So we do that now/here. For aliasing PPGTT, we
> - * will never need to touch the PDEs again */
> + * will never need to touch the PDEs again.
> + */
> for (i = 0; i < max_pdp; i++) {
> gen8_ppgtt_pde_t *pd_vaddr;
> pd_vaddr = kmap_atomic(&ppgtt->pd_pages[i]);
> @@ -461,6 +472,14 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt,
> uint64_t size)
> kunmap_atomic(pd_vaddr);
> }
>
> + ppgtt->enable = gen8_ppgtt_enable;
> + ppgtt->switch_mm = gen8_mm_switch;
> + ppgtt->base.clear_range = gen8_ppgtt_clear_range;
> + ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
> + ppgtt->base.cleanup = gen8_ppgtt_cleanup;
> + ppgtt->base.start = 0;
> + ppgtt->base.total = ppgtt->num_pt_pages * GEN8_PTES_PER_PAGE *
> PAGE_SIZE;
> +
> ppgtt->base.clear_range(&ppgtt->base, 0,
> ppgtt->num_pd_entries * GEN8_PTES_PER_PAGE,
> true);
> @@ -473,8 +492,9 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt,
> uint64_t size)
> size % (1<<30));
> return 0;
>
> -err_out:
> - ppgtt->base.cleanup(&ppgtt->base);
> +bail:
> + gen8_ppgtt_unmap_pages(ppgtt);
> + gen8_ppgtt_free(ppgtt);
> return ret;
> }
>
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