On Tue, Oct 15, 2024 at 11:41:56PM -0600, Kasireddy, Vivek wrote: > Hi Matt, > > > > > On Fri, Oct 11, 2024 at 07:40:26PM -0700, Vivek Kasireddy wrote: > > > For BOs of type ttm_bo_type_sg, that are backed by PCI BAR addresses > > > associated with a VF, we need to adjust and translate these addresses > > > to LMEM addresses to make the BOs usable by the PF. Otherwise, the BOs > > > (i.e, PCI BAR addresses) are only accessible by the CPU and not by > > > the GPU. > > > > > > In order to do the above, we first need to identify if the DMA addresses > > > associated with an imported BO (type ttm_bo_type_sg) belong to System > > > RAM or a VF or other PCI device. After we confirm that they belong to > > > a VF, we convert the DMA addresses (IOVAs in this case) to DPAs and > > > create a new sg and populate it with the new addresses. > > > > I think using a SG list is a no-go. We have received pushback before [1] > > about using a SG list as structure to hold DPA rather than dma-address. > > The consensus was a SG list is not a generic structure to hold any > > address [2], rather a specific structure for dma addressess. > AFAIU, that would make sense if the SG list was exposed outside of the Xe > driver but the SG list that is created by this patch is only used internally by > the Xe driver. Would this still not be acceptable? > I'd check with Thomas on this. I'm not hugely opposed, but if I remember correctly, Thomas agrees with Jason in the links below that SG lists shouldn't be used like this. Certainly, making this internal to Xe makes it safer, though. > > > > I'm pretty sure we will have define a new BO type (ttm_bo_type_devmem?) > > and structure that can iterated on if we want to do something like this > > unless we want to ignore the above feedback. > Right, if using SG list is a no-go, then using some form of xe_res_cursor to > iterate seems like the only other option. > Ah, yes. Since this is internal to Xe, it may be easy enough to use a different cursor type here rather than touching TTM. > > > > [1] https://patchwork.freedesktop.org/patch/574894/?series=128910&rev=1 > > [2] > > https://patchwork.freedesktop.org/patch/574894/?series=128910&rev=1#co > > mment_1070889 > > > > > > > > Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx> > > > --- > > > drivers/gpu/drm/xe/xe_bo.c | 108 > > ++++++++++++++++++++++++++++++- > > > drivers/gpu/drm/xe/xe_bo_types.h | 6 ++ > > > 2 files changed, 113 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c > > > index c74c121ea7bb..64efe1b21f19 100644 > > > --- a/drivers/gpu/drm/xe/xe_bo.c > > > +++ b/drivers/gpu/drm/xe/xe_bo.c > > > @@ -6,6 +6,7 @@ > > > #include "xe_bo.h" > > > > > > #include <linux/dma-buf.h> > > > +#include <linux/iommu.h> > > > > > > #include <drm/drm_drv.h> > > > #include <drm/drm_gem_ttm_helper.h> > > > @@ -15,16 +16,19 @@ > > > #include <drm/ttm/ttm_tt.h> > > > #include <uapi/drm/xe_drm.h> > > > > > > +#include "regs/xe_bars.h" > > > #include "xe_device.h" > > > #include "xe_dma_buf.h" > > > #include "xe_drm_client.h" > > > #include "xe_ggtt.h" > > > #include "xe_gt.h" > > > +#include "xe_gt_sriov_pf_config.h" > > > #include "xe_map.h" > > > #include "xe_migrate.h" > > > #include "xe_pm.h" > > > #include "xe_preempt_fence.h" > > > #include "xe_res_cursor.h" > > > +#include "xe_sriov_pf_helpers.h" > > > #include "xe_trace_bo.h" > > > #include "xe_ttm_stolen_mgr.h" > > > #include "xe_vm.h" > > > @@ -543,6 +547,102 @@ static int xe_bo_trigger_rebind(struct xe_device > > *xe, struct xe_bo *bo, > > > return ret; > > > } > > > > > > +static struct pci_dev *xe_find_vf_dev(struct xe_device *xe, > > > + phys_addr_t phys) > > > +{ > > > + struct pci_dev *pdev, *pf_pdev = to_pci_dev(xe->drm.dev); > > > + resource_size_t io_start, io_size; > > > + > > > + list_for_each_entry(pdev, &pf_pdev->bus->devices, bus_list) { > > > + if (pdev->is_physfn) > > > + continue; > > > + > > > + io_start = pci_resource_start(pdev, LMEM_BAR); > > > + io_size = pci_resource_len(pdev, LMEM_BAR); > > > + > > > + if (phys >= io_start && > > > + phys < (io_start + io_size - PAGE_SIZE)) > > > + return pdev; > > > + } > > > + return NULL; > > > +} > > > + > > > + > > > +static void xe_bo_translate_iova_to_dpa(struct xe_device *xe, > > > + struct sg_table *sg, > > > + struct sg_table *new_sg, > > > + struct pci_dev *pdev) > > > +{ > > > + resource_size_t io_start = pci_resource_start(pdev, LMEM_BAR); > > > + struct xe_gt *gt = xe_root_mmio_gt(xe); > > > + struct scatterlist *sgl, *new_sgl; > > > + int i, vfid = pci_iov_vf_id(pdev); > > > + dma_addr_t new_addr, bo_addr; > > > + struct iommu_domain *domain; > > > + phys_addr_t phys; > > > + u64 offset; > > > + > > > + bo_addr = xe_gt_sriov_pf_config_get_lmem_addr(gt, ++vfid); > > > + domain = iommu_get_domain_for_dev(xe->drm.dev); > > > + > > > + new_sgl = new_sg->sgl; > > > + for_each_sgtable_dma_sg(sg, sgl, i) { > > > > I'm pretty sure this doesn't work if a single dma address of the input > > 'sg' resolves to a non-contiguous physical DPA. In most cases this is > > going to be contiguous though unless there is memory pressure or > > unaligned allocations sizes. Assuming your testing didn't blow up, you > > may not have hit a memory pressure situation where VRAM gets > > fragmented. > Yeah, I did not test exhaustively and also did not realize that that the BO > (config->lmem_obj) backing the VF's lmem quota may not be contiguous. > I'll try to figure out a way to test this scenario. However, for each SG entry, > if I do something like: > > offset = phys - io_start; > new_addr = xe_bo_addr(config->lmem_obj, offset, sg_dma_len(sgl)); > > instead of > > bo_addr = xe_bo_addr(config->lmem_obj, 0, PAGE_SIZE); > offset = phys - io_start; > new_addr = bo_addr + offset; > > I believe this would probably work as expected even when lmem_obj is not > contiguous (as it probes the buddy blocks) or if input SG has non-contiguous > physical (DPA) ranges. > > > > > I think only iommu_iova_to_phys is accurate for exactly 1 page unless > > I'm missing something. See [3]. > IIUC, it seems to be valid for the segment of size sg_dma_len(sgl), for a given > SG entry. > So the SG list you are remapping here is set up in xe_dma_buf_map, specifically for the VRAM case of xe_ttm_vram_mgr_alloc_sgt, right? Yes, it appears each segment (sg_dma_len(sgl)) is a buddy block, so it is contiguous. This does work, but it makes a lot of assumptions about the lower layers, which is not ideal. Each segment is still a DMA address, so it’s possible that iommu_iova_to_phys is only accurate for exactly one page within the segment. I'd prefer to code for that behavior, which will always work, rather than making assumptions about a lower layer. With all of the above, can we add a page-by-page DPA cursor? Thomas has written one for SVM [4] [5]. That code will take a while to land, but I think it can give you a template to build a cursor like this. Once that lands, maybe we can combine these cursors. Matt [4] https://patchwork.freedesktop.org/patch/619812/?series=137870&rev=2 [5] https://patchwork.freedesktop.org/patch/619845/?series=137870&rev=2 > Thanks, > Vivek > > > > > [3] > > https://elixir.bootlin.com/linux/v6.11.3/source/drivers/iommu/iommu.c#L2 > > 376 > > > > Matt > > > > > + phys = domain ? iommu_iova_to_phys(domain, > > sg_dma_address(sgl)) : > > > + sg_dma_address(sgl); > > > + offset = phys - io_start; > > > + new_addr = bo_addr + offset; > > > + > > > + sg_set_page(new_sgl, NULL, sg_dma_len(sgl), 0); > > > + sg_dma_address(new_sgl) = new_addr; > > > + sg_dma_len(new_sgl) = sg_dma_len(sgl); > > > + > > > + new_sgl = sg_next(new_sgl); > > > + } > > > +} > > > + > > > +static struct sg_table *xe_bo_create_new_sg(struct sg_table *sg, > > > + struct xe_bo *bo) > > > +{ > > > + struct xe_device *xe = xe_bo_device(bo); > > > + struct iommu_domain *domain; > > > + struct sg_table *new_sg; > > > + struct pci_dev *pdev; > > > + phys_addr_t phys; > > > + int vfid; > > > + > > > + if (!IS_SRIOV_PF(xe)) > > > + return sg; > > > + > > > + domain = iommu_get_domain_for_dev(xe->drm.dev); > > > + phys = domain ? iommu_iova_to_phys(domain, sg_dma_address(sg- > > >sgl)) : > > > + sg_dma_address(sg->sgl); > > > + > > > + if (page_is_ram(PFN_DOWN(phys))) > > > + return sg; > > > + > > > + pdev = xe_find_vf_dev(xe, phys); > > > + if (!pdev) > > > + return sg; > > > + > > > + vfid = pci_iov_vf_id(pdev); > > > + if (vfid < 0) > > > + return sg; > > > + > > > + new_sg = kzalloc(sizeof(*new_sg), GFP_KERNEL); > > > + if (!new_sg) > > > + return sg; > > > + > > > + if (sg_alloc_table(new_sg, sg->nents, GFP_KERNEL)) { > > > + kfree(new_sg); > > > + return sg; > > > + } > > > + > > > + bo->is_devmem_external = true; > > > + xe_bo_translate_iova_to_dpa(xe, sg, new_sg, pdev); > > > + > > > + return new_sg; > > > +} > > > + > > > /* > > > * The dma-buf map_attachment() / unmap_attachment() is hooked up > > here. > > > * Note that unmapping the attachment is deferred to the next > > > @@ -577,7 +677,7 @@ static int xe_bo_move_dmabuf(struct > > ttm_buffer_object *ttm_bo, > > > return PTR_ERR(sg); > > > > > > ttm_bo->sg = sg; > > > - xe_tt->sg = sg; > > > + xe_tt->sg = xe_bo_create_new_sg(sg, ttm_to_xe_bo(ttm_bo)); > > > > > > out: > > > ttm_bo_move_null(ttm_bo, new_res); > > > @@ -1066,6 +1166,8 @@ static void xe_ttm_bo_release_notify(struct > > ttm_buffer_object *ttm_bo) > > > > > > static void xe_ttm_bo_delete_mem_notify(struct ttm_buffer_object > > *ttm_bo) > > > { > > > + struct xe_bo *bo = ttm_to_xe_bo(ttm_bo); > > > + > > > if (!xe_bo_is_xe_bo(ttm_bo)) > > > return; > > > > > > @@ -1079,6 +1181,10 @@ static void > > xe_ttm_bo_delete_mem_notify(struct ttm_buffer_object *ttm_bo) > > > > > > dma_buf_unmap_attachment(ttm_bo->base.import_attach, > > ttm_bo->sg, > > > DMA_BIDIRECTIONAL); > > > + if (bo->is_devmem_external && xe_tt->sg != ttm_bo->sg) { > > > + sg_free_table(xe_tt->sg); > > > + kfree(xe_tt->sg); > > > + } > > > ttm_bo->sg = NULL; > > > xe_tt->sg = NULL; > > > } > > > diff --git a/drivers/gpu/drm/xe/xe_bo_types.h > > b/drivers/gpu/drm/xe/xe_bo_types.h > > > index 8b9201775081..0fe619bc436d 100644 > > > --- a/drivers/gpu/drm/xe/xe_bo_types.h > > > +++ b/drivers/gpu/drm/xe/xe_bo_types.h > > > @@ -67,6 +67,12 @@ struct xe_bo { > > > /** @ccs_cleared */ > > > bool ccs_cleared; > > > > > > + /** > > > + * @is_devmem_external: Whether this BO is an imported dma-buf > > that > > > + * has a backing store in VRAM. > > > + */ > > > + bool is_devmem_external; > > > + > > > /** > > > * @cpu_caching: CPU caching mode. Currently only used for > > userspace > > > * objects. Exceptions are system memory on DGFX, which is always > > > -- > > > 2.45.1 > > >
