[PATCH 1/5] drm/xe/svm: Remap and provide memmap backing for GPU vram
Zeng, Oak
oak.zeng at intel.com
Fri Mar 15 03:10:10 UTC 2024
> -----Original Message-----
> From: Welty, Brian <brian.welty at intel.com>
> Sent: Thursday, March 14, 2024 9:46 PM
> To: Zeng, Oak <oak.zeng at intel.com>; intel-xe at lists.freedesktop.org
> Cc: Hellstrom, Thomas <thomas.hellstrom at intel.com>; Brost, Matthew
> <matthew.brost at intel.com>; airlied at gmail.com; Ghimiray, Himal Prasad
> <himal.prasad.ghimiray at intel.com>
> Subject: Re: [PATCH 1/5] drm/xe/svm: Remap and provide memmap backing for
> GPU vram
>
> Hi Oak,
>
> On 3/13/2024 8:35 PM, Oak Zeng wrote:
> > Memory remap GPU vram using devm_memremap_pages, so each GPU vram
> > page is backed by a struct page.
> >
> > Those struct pages are created to allow hmm migrate buffer b/t
> > GPU vram and CPU system memory using existing Linux migration
> > mechanism (i.e., migrating b/t CPU system memory and hard disk).
> >
> > This is prepare work to enable svm (shared virtual memory) through
> > Linux kernel hmm framework. The memory remap's page map type is set
> > to MEMORY_DEVICE_PRIVATE for now. This means even though each GPU
> > vram page get a struct page and can be mapped in CPU page table,
> > but such pages are treated as GPU's private resource, so CPU can't
> > access them. If CPU access such page, a page fault is triggered
> > and page will be migrate to system memory.
> >
> > For GPU device which supports coherent memory protocol b/t CPU and
> > GPU (such as CXL and CAPI protocol), we can remap device memory as
> > MEMORY_DEVICE_COHERENT. This is TBD.
> >
> > Signed-off-by: Oak Zeng <oak.zeng at intel.com>
> > Co-developed-by: Niranjana Vishwanathapura
> <niranjana.vishwanathapura at intel.com>
> > Signed-off-by: Niranjana Vishwanathapura
> <niranjana.vishwanathapura at intel.com>
> > Cc: Matthew Brost <matthew.brost at intel.com>
> > Cc: Thomas Hellström <thomas.hellstrom at intel.com>
> > Cc: Brian Welty <brian.welty at intel.com>
> > ---
> > drivers/gpu/drm/xe/Makefile | 3 +-
> > drivers/gpu/drm/xe/xe_device_types.h | 9 +++
> > drivers/gpu/drm/xe/xe_mmio.c | 8 +++
> > drivers/gpu/drm/xe/xe_svm.h | 14 +++++
> > drivers/gpu/drm/xe/xe_svm_devmem.c | 91
> ++++++++++++++++++++++++++++
> > 5 files changed, 124 insertions(+), 1 deletion(-)
> > create mode 100644 drivers/gpu/drm/xe/xe_svm.h
> > create mode 100644 drivers/gpu/drm/xe/xe_svm_devmem.c
> >
> > diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> > index c531210695db..840467080e59 100644
> > --- a/drivers/gpu/drm/xe/Makefile
> > +++ b/drivers/gpu/drm/xe/Makefile
> > @@ -142,7 +142,8 @@ xe-y += xe_bb.o \
> > xe_vram_freq.o \
> > xe_wait_user_fence.o \
> > xe_wa.o \
> > - xe_wopcm.o
> > + xe_wopcm.o \
> > + xe_svm_devmem.o
>
> Minor, but maintainers want above alphabetically sorted.
Correct. Matt pointed out the same. Will fix
>
> >
> > # graphics hardware monitoring (HWMON) support
> > xe-$(CONFIG_HWMON) += xe_hwmon.o
> > diff --git a/drivers/gpu/drm/xe/xe_device_types.h
> b/drivers/gpu/drm/xe/xe_device_types.h
> > index 9785eef2e5a4..f27c3bee8ce7 100644
> > --- a/drivers/gpu/drm/xe/xe_device_types.h
> > +++ b/drivers/gpu/drm/xe/xe_device_types.h
> > @@ -99,6 +99,15 @@ struct xe_mem_region {
> > resource_size_t actual_physical_size;
> > /** @mapping: pointer to VRAM mappable space */
> > void __iomem *mapping;
> > + /** @pagemap: Used to remap device memory as ZONE_DEVICE */
> > + struct dev_pagemap pagemap;
> > + /**
> > + * @hpa_base: base host physical address
> > + *
> > + * This is generated when remap device memory as ZONE_DEVICE
> > + */
> > + resource_size_t hpa_base;
> > +
> > };
> >
> > /**
> > diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> > index e3db3a178760..0d795394bc4c 100644
> > --- a/drivers/gpu/drm/xe/xe_mmio.c
> > +++ b/drivers/gpu/drm/xe/xe_mmio.c
> > @@ -22,6 +22,7 @@
> > #include "xe_module.h"
> > #include "xe_sriov.h"
> > #include "xe_tile.h"
> > +#include "xe_svm.h"
> >
> > #define XEHP_MTCFG_ADDR XE_REG(0x101800)
> > #define TILE_COUNT REG_GENMASK(15, 8)
> > @@ -286,6 +287,7 @@ int xe_mmio_probe_vram(struct xe_device *xe)
> > }
> >
> > io_size -= min_t(u64, tile_size, io_size);
> > + xe_svm_devm_add(tile, &tile->mem.vram);
>
> I think slightly more appropriate call site for this might be
> xe_tile_init_noalloc(), as that function states it is preparing tile
> for VRAM allocations.
> Also, I mention because we might like the flexiblity in future to call
> this once for xe_device.mem.vram, instead of calling for each tile,
> and easier to handle that in xe_tile.c instead of xe_mmio.c.
Good point. Will follow.
>
> Related comment below.
>
>
> > }
> >
> > xe->mem.vram.actual_physical_size = total_size;
> > @@ -354,10 +356,16 @@ void xe_mmio_probe_tiles(struct xe_device *xe)
> > static void mmio_fini(struct drm_device *drm, void *arg)
> > {
> > struct xe_device *xe = arg;
> > + struct xe_tile *tile;
> > + u8 id;
> >
> > pci_iounmap(to_pci_dev(xe->drm.dev), xe->mmio.regs);
> > if (xe->mem.vram.mapping)
> > iounmap(xe->mem.vram.mapping);
> > +
> > + for_each_tile(tile, xe, id)
> > + xe_svm_devm_remove(xe, &tile->mem.vram);
> > +
> > }
> >
> > static int xe_verify_lmem_ready(struct xe_device *xe)
> > diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
> > new file mode 100644
> > index 000000000000..09f9afb0e7d4
> > --- /dev/null
> > +++ b/drivers/gpu/drm/xe/xe_svm.h
> > @@ -0,0 +1,14 @@
> > +// SPDX-License-Identifier: MIT
> > +/*
> > + * Copyright © 2023 Intel Corporation
> > + */
> > +
> > +#ifndef __XE_SVM_H
> > +#define __XE_SVM_H
> > +
> > +#include "xe_device_types.h"
> > +
> > +int xe_svm_devm_add(struct xe_tile *tile, struct xe_mem_region *mem);
> > +void xe_svm_devm_remove(struct xe_device *xe, struct xe_mem_region
> *mem);
> > +
> > +#endif
> > diff --git a/drivers/gpu/drm/xe/xe_svm_devmem.c
> b/drivers/gpu/drm/xe/xe_svm_devmem.c
> > new file mode 100644
> > index 000000000000..63b7a1961cc6
> > --- /dev/null
> > +++ b/drivers/gpu/drm/xe/xe_svm_devmem.c
> > @@ -0,0 +1,91 @@
> > +// SPDX-License-Identifier: MIT
> > +/*
> > + * Copyright © 2023 Intel Corporation
> > + */
> > +
> > +#include <linux/mm_types.h>
> > +#include <linux/sched/mm.h>
> > +
> > +#include "xe_device_types.h"
> > +#include "xe_trace.h"
> > +#include "xe_svm.h"
> > +
> > +
> > +static vm_fault_t xe_devm_migrate_to_ram(struct vm_fault *vmf)
> > +{
> > + return 0;
> > +}
> > +
> > +static void xe_devm_page_free(struct page *page)
> > +{
> > +}
> > +
> > +static const struct dev_pagemap_ops xe_devm_pagemap_ops = {
> > + .page_free = xe_devm_page_free,
> > + .migrate_to_ram = xe_devm_migrate_to_ram,
> > +};
> > +
> > +/**
> > + * xe_svm_devm_add: Remap and provide memmap backing for device
> memory
>
> Do we really need 'svm' in function name?
Good point. I will remove svm.
>
> > + * @tile: tile that the memory region blongs to
>
> We might like flexibility in future to call this once for
> xe_device.mem.vram, instead of calling for each tile.
> So can we remove the tile argument, and just pass the xe_device pointer
> and tile->id ?
This is interesting.
First of all, I programmed wrong below: mr->pagemap.owner = tile->xe->drm.dev;
This should be: mr->pagemap.owner = tile for NUMA vram system.
For UMA vram, this should be: mr->pagemap.owner = tile_to_xe(tile);
This owner is important. It is used later to decide migration by hmm. We need to set the owner for hmm to identify different vram region.
Based on above, I think the tile parameter is better. For UMA, caller need to make sure call it once, any tile pointer should work. This does sound a little weird. But I don’t have a better idea.
Oak
>
>
> > + * @mr: memory region to remap
> > + *
> > + * This remap device memory to host physical address space and create
> > + * struct page to back device memory
> > + *
> > + * Return: 0 on success standard error code otherwise
> > + */
> > +int xe_svm_devm_add(struct xe_tile *tile, struct xe_mem_region *mr)
> > +{
> > + struct device *dev = &to_pci_dev(tile->xe->drm.dev)->dev;
> > + struct resource *res;
> > + void *addr;
> > + int ret;
> > +
> > + res = devm_request_free_mem_region(dev, &iomem_resource,
> > + mr->usable_size);
> > + if (IS_ERR(res)) {
> > + ret = PTR_ERR(res);
> > + return ret;
> > + }
> > +
> > + mr->pagemap.type = MEMORY_DEVICE_PRIVATE;
> > + mr->pagemap.range.start = res->start;
> > + mr->pagemap.range.end = res->end;
> > + mr->pagemap.nr_range = 1;
> > + mr->pagemap.ops = &xe_devm_pagemap_ops;
> > + mr->pagemap.owner = tile->xe->drm.dev;
> > + addr = devm_memremap_pages(dev, &mr->pagemap);
> > + if (IS_ERR(addr)) {
> > + devm_release_mem_region(dev, res->start, resource_size(res));
> > + ret = PTR_ERR(addr);
> > + drm_err(&tile->xe->drm, "Failed to remap tile %d memory,
> errno %d\n",
> > + tile->id, ret);
> > + return ret;
> > + }
> > + mr->hpa_base = res->start;
> > +
> > + drm_info(&tile->xe->drm, "Added tile %d memory [%llx-%llx] to devm,
> remapped to %pr\n",
> > + tile->id, mr->io_start, mr->io_start + mr->usable_size,
> res);
> > + return 0;
> > +}
> > +
> > +/**
> > + * xe_svm_devm_remove: Unmap device memory and free resources
> > + * @xe: xe device
> > + * @mr: memory region to remove
> > + */
> > +void xe_svm_devm_remove(struct xe_device *xe, struct xe_mem_region
> *mr)
> > +{
> > + /*FIXME: below cause a kernel hange during moduel remove*/
> > +#if 0
> > + struct device *dev = &to_pci_dev(xe->drm.dev)->dev;
> > +
> > + if (mr->hpa_base) {
> > + devm_memunmap_pages(dev, &mr->pagemap);
> > + devm_release_mem_region(dev, mr->pagemap.range.start,
> > + mr->pagemap.range.end - mr->pagemap.range.start +1);
> > + }
> > +#endif
> > +}
> > +
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