Mimic the dma-buf method using dma_[map|unmap]_resource to map for pcie-p2p dma.
There's an ongoing area of work upstream to sort out how this best should be done. One method proposed is to add an additional pci_p2p_dma_pagemap aliasing the device_private pagemap and use the corresponding pci_p2p_dma_pagemap page as input for dma_map_page(). However, that would incur double the amount of memory and latency to set up the drm_pagemap and given the huge amount of memory present on modern GPUs, that would really not work. Hence the simple approach used in this patch. v2: - Simplify xe_page_to_pcie(). (Matt Brost) Signed-off-by: Thomas Hellström <[email protected]> --- drivers/gpu/drm/xe/xe_svm.c | 34 +++++++++++++++++++++++++++++++--- drivers/gpu/drm/xe/xe_svm.h | 1 + 2 files changed, 32 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c index c0b17b548a00..86d7b0882b60 100644 --- a/drivers/gpu/drm/xe/xe_svm.c +++ b/drivers/gpu/drm/xe/xe_svm.c @@ -3,6 +3,8 @@ * Copyright © 2024 Intel Corporation */ +#include <linux/pci-p2pdma.h> + #include <drm/drm_drv.h> #include <drm/drm_managed.h> #include <drm/drm_pagemap.h> @@ -441,6 +443,14 @@ static u64 xe_page_to_dpa(struct page *page) return dpa; } +static u64 xe_page_to_pcie(struct page *page) +{ + struct xe_pagemap *xpagemap = xe_page_to_pagemap(page); + struct xe_vram_region *vr = xe_pagemap_to_vr(xpagemap); + + return xe_page_to_dpa(page) - vr->dpa_base + vr->io_start; +} + enum xe_svm_copy_dir { XE_SVM_COPY_TO_VRAM, XE_SVM_COPY_TO_SRAM, @@ -792,7 +802,10 @@ static bool xe_has_interconnect(struct drm_pagemap_peer *peer1, struct device *dev1 = xe_peer_to_dev(peer1); struct device *dev2 = xe_peer_to_dev(peer2); - return dev1 == dev2; + if (dev1 == dev2) + return true; + + return pci_p2pdma_distance(to_pci_dev(dev1), dev2, true) >= 0; } static DRM_PAGEMAP_OWNER_LIST_DEFINE(xe_owner_list); @@ -1552,13 +1565,27 @@ xe_drm_pagemap_device_map(struct drm_pagemap *dpagemap, addr = xe_page_to_dpa(page); prot = XE_INTERCONNECT_VRAM; } else { - addr = DMA_MAPPING_ERROR; - prot = 0; + addr = dma_map_resource(dev, + xe_page_to_pcie(page), + PAGE_SIZE << order, dir, + DMA_ATTR_SKIP_CPU_SYNC); + prot = XE_INTERCONNECT_P2P; } return drm_pagemap_addr_encode(addr, prot, order, dir); } +static void xe_drm_pagemap_device_unmap(struct drm_pagemap *dpagemap, + struct device *dev, + struct drm_pagemap_addr addr) +{ + if (addr.proto != XE_INTERCONNECT_P2P) + return; + + dma_unmap_resource(dev, addr.addr, PAGE_SIZE << addr.order, + addr.dir, DMA_ATTR_SKIP_CPU_SYNC); +} + static void xe_pagemap_destroy_work(struct work_struct *work) { struct xe_pagemap *xpagemap = container_of(work, typeof(*xpagemap), destroy_work); @@ -1595,6 +1622,7 @@ static void xe_pagemap_destroy(struct drm_pagemap *dpagemap, bool from_atomic_or static const struct drm_pagemap_ops xe_drm_pagemap_ops = { .device_map = xe_drm_pagemap_device_map, + .device_unmap = xe_drm_pagemap_device_unmap, .populate_mm = xe_drm_pagemap_populate_mm, .destroy = xe_pagemap_destroy, }; diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h index 60eae01a4220..64971c9b2a1a 100644 --- a/drivers/gpu/drm/xe/xe_svm.h +++ b/drivers/gpu/drm/xe/xe_svm.h @@ -13,6 +13,7 @@ #include <drm/drm_pagemap_util.h> #define XE_INTERCONNECT_VRAM DRM_INTERCONNECT_DRIVER +#define XE_INTERCONNECT_P2P (XE_INTERCONNECT_VRAM + 1) struct drm_device; struct drm_file; -- 2.51.1
