On 29/01/2025 19:51, Matthew Brost wrote:
This patch introduces support for GPU Shared Virtual Memory (SVM) in the
Direct Rendering Manager (DRM) subsystem. SVM allows for seamless
sharing of memory between the CPU and GPU, enhancing performance and
flexibility in GPU computing tasks.
The patch adds the necessary infrastructure for SVM, including data
structures and functions for managing SVM ranges and notifiers. It also
provides mechanisms for allocating, deallocating, and migrating memory
regions between system RAM and GPU VRAM.
This is largely inspired by GPUVM.
v2:
- Take order into account in check pages
- Clear range->pages in get pages error
- Drop setting dirty or accessed bit in get pages (Vetter)
- Remove mmap assert for cpu faults
- Drop mmap write lock abuse (Vetter, Christian)
- Decouple zdd from range (Vetter, Oak)
- Add drm_gpusvm_range_evict, make it work with coherent pages
- Export drm_gpusvm_evict_to_sram, only use in BO evict path (Vetter)
- mmget/put in drm_gpusvm_evict_to_sram
- Drop range->vram_alloation variable
- Don't return in drm_gpusvm_evict_to_sram until all pages detached
- Don't warn on mixing sram and device pages
- Update kernel doc
- Add coherent page support to get pages
- Use DMA_FROM_DEVICE rather than DMA_BIDIRECTIONAL
- Add struct drm_gpusvm_vram and ops (Thomas)
- Update the range's seqno if the range is valid (Thomas)
- Remove the is_unmapped check before hmm_range_fault (Thomas)
- Use drm_pagemap (Thomas)
- Drop kfree_mapping (Thomas)
- dma mapp pages under notifier lock (Thomas)
- Remove ctx.prefault
- Remove ctx.mmap_locked
- Add ctx.check_pages
- s/vram/devmem (Thomas)
v3:
- Fix memory leak drm_gpusvm_range_get_pages
- Only migrate pages with same zdd on CPU fault
- Loop over al VMAs in drm_gpusvm_range_evict
- Make GPUSVM a drm level module
- GPL or MIT license
- Update main kernel doc (Thomas)
- Prefer foo() vs foo for functions in kernel doc (Thomas)
- Prefer functions over macros (Thomas)
- Use unsigned long vs u64 for addresses (Thomas)
- Use standard interval_tree (Thomas)
- s/drm_gpusvm_migration_put_page/
drm_gpusvm_migration_unlock_put_page (Thomas)
- Drop err_out label in drm_gpusvm_range_find_or_insert (Thomas)
- Fix kernel doc in drm_gpusvm_range_free_pages (Thomas)
- Newlines between functions defs in header file (Thomas)
- Drop shall language in driver vfunc kernel doc (Thomas)
- Move some static inlines from head to C file (Thomas)
- Don't allocate pages under page lock in
drm_gpusvm_migrate_populate_ram_pfn (Thomas)
- Change check_pages to a threshold
v4:
- Fix NULL ptr deref in drm_gpusvm_migrate_populate_ram_pfn (Thomas,
Himal)
- Fix check pages threshold
- Check for range being unmapped under notifier lock in get pages
(Testing)
- Fix characters per line
- Drop WRITE_ONCE for zdd->devmem_allocation assignment (Thomas)
- Use completion for devmem_allocation->detached (Thomas)
- Make GPU SVM depend on ZONE_DEVICE (CI)
- Use hmm_range_fault for eviction (Thomas)
- Drop zdd worker (Thomas)
Cc: Simona Vetter <simona.vetter@xxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: <dri-devel@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
<snip>
+/**
+ * __drm_gpusvm_migrate_to_ram() - Migrate GPU SVM range to RAM
(internal)
+ * @vas: Pointer to the VM area structure
+ * @device_private_page_owner: Device private pages owner
+ * @page: Pointer to the page for fault handling (can be NULL)
+ * @fault_addr: Fault address
+ * @size: Size of migration
+ *
+ * This internal function performs the migration of the specified GPU
SVM range
+ * to RAM. It sets up the migration, populates + dma maps RAM PFNs, and
+ * invokes the driver-specific operations for migration to RAM.
+ *
+ * Returns:
+ * 0 on success, negative error code on failure.
+ */
+static int __drm_gpusvm_migrate_to_ram(struct vm_area_struct *vas,
+ void *device_private_page_owner,
+ struct page *page,
+ unsigned long fault_addr,
+ unsigned long size)
+{
+ struct migrate_vma migrate = {
+ .vma = vas,
+ .pgmap_owner = device_private_page_owner,
+ .flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE |
+ MIGRATE_VMA_SELECT_DEVICE_COHERENT,
+ .fault_page = page,
+ };
+ struct drm_gpusvm_zdd *zdd;
+ const struct drm_gpusvm_devmem_ops *ops;
+ struct device *dev;
+ unsigned long npages, mpages = 0;
+ struct page **pages;
+ dma_addr_t *dma_addr;
+ unsigned long start, end;
+ void *buf;
+ int i, err = 0;
+
+ start = ALIGN_DOWN(fault_addr, size);
+ end = ALIGN(fault_addr + 1, size);
+
+ /* Corner where VMA area struct has been partially unmapped */
+ if (start < vas->vm_start)
+ start = vas->vm_start;
+ if (end > vas->vm_end)
+ end = vas->vm_end;
+
+ migrate.start = start;
+ migrate.end = end;
+ npages = npages_in_range(start, end);
+
+ buf = kvcalloc(npages, 2 * sizeof(*migrate.src) +
sizeof(*dma_addr) +
+ sizeof(*pages), GFP_KERNEL);
+ if (!buf) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ dma_addr = buf + (2 * sizeof(*migrate.src) * npages);
+ pages = buf + (2 * sizeof(*migrate.src) + sizeof(*dma_addr)) *
npages;
+
+ migrate.vma = vas;
+ migrate.src = buf;
+ migrate.dst = migrate.src + npages;
+
+ err = migrate_vma_setup(&migrate);
+ if (err)
+ goto err_free;
+
+ /* Raced with another CPU fault, nothing to do */
+ if (!migrate.cpages)
+ goto err_free;
+
+ if (!page) {
+ for (i = 0; i < npages; ++i) {
+ if (!(migrate.src[i] & MIGRATE_PFN_MIGRATE))
+ continue;
+
+ page = migrate_pfn_to_page(migrate.src[i]);
+ break;
+ }
+
+ if (!page)
+ goto err_finalize;
+ }
+ zdd = page->zone_device_data;
+ ops = zdd->devmem_allocation->ops;
+ dev = zdd->devmem_allocation->dev;
+
+ err = drm_gpusvm_migrate_populate_ram_pfn(vas, page, npages,
&mpages,
+ migrate.src, migrate.dst,
+ start);
+ if (err)
+ goto err_finalize;
+
+ err = drm_gpusvm_migrate_map_pages(dev, dma_addr, migrate.dst,
npages,
+ DMA_FROM_DEVICE);
+ if (err)
+ goto err_finalize;
+
+ for (i = 0; i < npages; ++i)
+ pages[i] = migrate_pfn_to_page(migrate.src[i]);
+
+ err = ops->copy_to_ram(pages, dma_addr, npages);
+ if (err)
+ goto err_finalize;
+
+err_finalize:
+ if (err)
+ drm_gpusvm_migration_unlock_put_pages(npages, migrate.dst);
+ migrate_vma_pages(&migrate);
+ migrate_vma_finalize(&migrate);
+ drm_gpusvm_migrate_unmap_pages(dev, dma_addr, npages,
+ DMA_FROM_DEVICE);
clang for me is throwing:
drivers/gpu/drm/drm_gpusvm.c:2017:7: error: variable 'dev' is used
uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-
uninitialized]
2017 | if (!page)
| ^~~~~
drivers/gpu/drm/drm_gpusvm.c:2047:33: note: uninitialized use occurs here
2047 | drm_gpusvm_migrate_unmap_pages(dev, dma_addr, npages,
| ^~~
drivers/gpu/drm/drm_gpusvm.c:2017:3: note: remove the 'if' if its
condition is always false
2017 | if (!page)
| ^~~~~~~~~~
2018 | goto err_finalize;
| ~~~~~~~~~~~~~~~~~
drivers/gpu/drm/drm_gpusvm.c:1966:20: note: initialize the variable
'dev' to silence this warning
1966 | struct device *dev;
| ^
| = NULL
1 error generated.
