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drm/gpusvm: Use dma-map IOVA alloc, link, and sync API in GPU SVM

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The dma-map IOVA alloc, link, and sync APIs perform significantly better
than dma-map / dma-unmap, as they avoid costly IOMMU synchronizations.
This difference is especially noticeable when mapping a 2MB region in
4KB pages.

Use the IOVA alloc, link, and sync APIs for GPU SVM, which create DMA
mappings between the CPU and GPU.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20260410205929.3914474-2-matthew.brost@intel.com
This commit is contained in:
Matthew Brost
2026-04-10 13:59:25 -07:00
parent efcd474ed2
commit 37ad039fb3
2 changed files with 50 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
drivers/gpu/drm/drm_gpusvm.c
View File

@@ -1139,11 +1139,17 @@ static void __drm_gpusvm_unmap_pages(struct drm_gpusvm *gpusvm,
struct drm_gpusvm_pages_flags flags = {
.__flags = svm_pages->flags.__flags,
};
bool use_iova = dma_use_iova(&svm_pages->state);
if (use_iova)
dma_iova_destroy(dev, &svm_pages->state,
svm_pages->state_offset,
svm_pages->dma_addr[0].dir, 0);
for (i = 0, j = 0; i < npages; j++) {
struct drm_pagemap_addr *addr = &svm_pages->dma_addr[j];
if (addr->proto == DRM_INTERCONNECT_SYSTEM)
if (!use_iova && addr->proto == DRM_INTERCONNECT_SYSTEM)
dma_unmap_page(dev,
addr->addr,
PAGE_SIZE << addr->order,
@@ -1408,6 +1414,7 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
struct drm_gpusvm_pages_flags flags;
enum dma_data_direction dma_dir = ctx->read_only ? DMA_TO_DEVICE :
DMA_BIDIRECTIONAL;
struct dma_iova_state *state = &svm_pages->state;
retry:
if (time_after(jiffies, timeout))
@@ -1446,6 +1453,9 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
if (err)
goto err_free;
*state = (struct dma_iova_state){};
svm_pages->state_offset = 0;
map_pages:
/*
* Perform all dma mappings under the notifier lock to not
@@ -1539,13 +1549,33 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
goto err_unmap;
}
addr = dma_map_page(gpusvm->drm->dev,
page, 0,
PAGE_SIZE << order,
dma_dir);
if (dma_mapping_error(gpusvm->drm->dev, addr)) {
err = -EFAULT;
goto err_unmap;
if (!i)
dma_iova_try_alloc(gpusvm->drm->dev, state,
npages * PAGE_SIZE >=
HPAGE_PMD_SIZE ?
HPAGE_PMD_SIZE : 0,
npages * PAGE_SIZE);
if (dma_use_iova(state)) {
err = dma_iova_link(gpusvm->drm->dev, state,
hmm_pfn_to_phys(pfns[i]),
svm_pages->state_offset,
PAGE_SIZE << order,
dma_dir, 0);
if (err)
goto err_unmap;
addr = state->addr + svm_pages->state_offset;
svm_pages->state_offset += PAGE_SIZE << order;
} else {
addr = dma_map_page(gpusvm->drm->dev,
page, 0,
PAGE_SIZE << order,
dma_dir);
if (dma_mapping_error(gpusvm->drm->dev, addr)) {
err = -EFAULT;
goto err_unmap;
}
}
svm_pages->dma_addr[j] = drm_pagemap_addr_encode
@@ -1557,6 +1587,13 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
flags.has_dma_mapping = true;
}
if (dma_use_iova(state)) {
err = dma_iova_sync(gpusvm->drm->dev, state, 0,
svm_pages->state_offset);
if (err)
goto err_unmap;
}
if (pagemap) {
flags.has_devmem_pages = true;
drm_pagemap_get(dpagemap);

5
include/drm/drm_gpusvm.h
View File

@@ -6,6 +6,7 @@
#ifndef __DRM_GPUSVM_H__
#define __DRM_GPUSVM_H__
#include <linux/dma-mapping.h>
#include <linux/kref.h>
#include <linux/interval_tree.h>
#include <linux/mmu_notifier.h>
@@ -136,6 +137,8 @@ struct drm_gpusvm_pages_flags {
* @dma_addr: Device address array
* @dpagemap: The struct drm_pagemap of the device pages we're dma-mapping.
* Note this is assuming only one drm_pagemap per range is allowed.
* @state: DMA IOVA state for mapping.
* @state_offset: DMA IOVA offset for mapping.
* @notifier_seq: Notifier sequence number of the range's pages
* @flags: Flags for range
* @flags.migrate_devmem: Flag indicating whether the range can be migrated to device memory
@@ -147,6 +150,8 @@ struct drm_gpusvm_pages_flags {
struct drm_gpusvm_pages {
struct drm_pagemap_addr *dma_addr;
struct drm_pagemap *dpagemap;
struct dma_iova_state state;
unsigned long state_offset;
unsigned long notifier_seq;
struct drm_gpusvm_pages_flags flags;
};