[PATCH v4 06/33] drm/gpusvm: Add support for GPU Shared Virtual Memory
Gwan-gyeong Mun
gwan-gyeong.mun at intel.com
Thu Jan 30 13:13:22 UTC 2025
On 1/30/25 1:17 PM, Matthew Auld wrote:
> 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 at ffwll.ch>
>> Cc: Dave Airlie <airlied at redhat.com>
>> Cc: Christian König <christian.koenig at amd.com>
>> Cc: <dri-devel at lists.freedesktop.org>
>> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
>> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
>> ---
>
> <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.
I also reported this issue in the v3 patch, but it doesn't seem to have
been fixed in v4 yet.
https://lore.kernel.org/dri-devel/0416fa97-1734-4565-a352-f045a6c0a15a@intel.com/
Br,
G.G.
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