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Message-ID: <ec276ac2-a346-5728-4ac6-9c9bd9ffcd41@amd.com>
Date: Wed, 22 Apr 2020 13:52:32 -0400
From: Felix Kuehling <felix.kuehling@....com>
To: Jason Gunthorpe <jgg@...pe.ca>, linux-mm@...ck.org,
Ralph Campbell <rcampbell@...dia.com>,
"Yang, Philip" <Philip.Yang@....com>
Cc: Alex Deucher <alexander.deucher@....com>,
amd-gfx@...ts.freedesktop.org, Ben Skeggs <bskeggs@...hat.com>,
Christian König <christian.koenig@....com>,
"David (ChunMing) Zhou" <David1.Zhou@....com>,
dri-devel@...ts.freedesktop.org, Christoph Hellwig <hch@....de>,
intel-gfx@...ts.freedesktop.org,
Jérôme Glisse <jglisse@...hat.com>,
John Hubbard <jhubbard@...dia.com>,
linux-kernel@...r.kernel.org,
Niranjana Vishwanathapura <niranjana.vishwanathapura@...el.com>,
nouveau@...ts.freedesktop.org
Subject: Re: [PATCH hmm 5/5] mm/hmm: remove the customizable pfn format from
hmm_range_fault
[+Philip Yang]
Am 2020-04-21 um 8:21 p.m. schrieb Jason Gunthorpe:
> From: Jason Gunthorpe <jgg@...lanox.com>
>
> Presumably the intent here was that hmm_range_fault() could put the data
> into some HW specific format and thus avoid some work. However, nothing
> actually does that, and it isn't clear how anything actually could do that
> as hmm_range_fault() provides CPU addresses which must be DMA mapped.
>
> Perhaps there is some special HW that does not need DMA mapping, but we
> don't have any examples of this, and the theoretical performance win of
> avoiding an extra scan over the pfns array doesn't seem worth the
> complexity. Plus pfns needs to be scanned anyhow to sort out any
> DEVICE_PRIVATE pages.
>
> This version replaces the uint64_t with an usigned long containing a pfn
> and fix flags. On input flags is filled with the HMM_PFN_REQ_* values, on
> successful output it is filled with HMM_PFN_* values, describing the state
> of the pages.
>
> amdgpu is simple to convert, it doesn't use snapshot and doesn't use
> per-page flags.
>
> nouveau uses only 16 hmm_pte entries at most (ie fits in a few cache
> lines), and it sweeps over its pfns array a couple of times anyhow.
>
> Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
> Signed-off-by: Christoph Hellwig <hch@....de>
Hi Jason,
I pointed out a typo in the documentation inline. Other than that, the
series is
Acked-by: Felix Kuehling <Felix.Kuehling@....com>
I'll try to build it and run some basic tests later.
> ---
> Documentation/vm/hmm.rst | 26 ++--
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 35 ++----
> drivers/gpu/drm/nouveau/nouveau_dmem.c | 60 +++++++--
> drivers/gpu/drm/nouveau/nouveau_dmem.h | 4 +-
> drivers/gpu/drm/nouveau/nouveau_svm.c | 52 ++++----
> include/linux/hmm.h | 99 ++++++---------
> mm/hmm.c | 160 +++++++++++-------------
> 7 files changed, 204 insertions(+), 232 deletions(-)
>
> diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
> index 9924f2caa0184c..73a9b8c858e5d9 100644
> --- a/Documentation/vm/hmm.rst
> +++ b/Documentation/vm/hmm.rst
> @@ -185,9 +185,6 @@ The usage pattern is::
> range.start = ...;
> range.end = ...;
> range.pfns = ...;
> - range.flags = ...;
> - range.values = ...;
> - range.pfn_shift = ...;
>
> if (!mmget_not_zero(interval_sub->notifier.mm))
> return -EFAULT;
> @@ -229,15 +226,10 @@ The hmm_range struct has 2 fields, default_flags and pfn_flags_mask, that specif
> fault or snapshot policy for the whole range instead of having to set them
> for each entry in the pfns array.
>
> -For instance, if the device flags for range.flags are::
> +For instance if the device driver wants pages for a range with at least read
> +permission, it sets::
>
> - range.flags[HMM_PFN_VALID] = (1 << 63);
> - range.flags[HMM_PFN_WRITE] = (1 << 62);
> -
> -and the device driver wants pages for a range with at least read permission,
> -it sets::
> -
> - range->default_flags = (1 << 63);
> + range->default_flags = HMM_PFN_REQ_VALID;
This should be HMM_PFN_REQ_FAULT.
> range->pfn_flags_mask = 0;
>
> and calls hmm_range_fault() as described above. This will fill fault all pages
> @@ -246,18 +238,18 @@ in the range with at least read permission.
> Now let's say the driver wants to do the same except for one page in the range for
> which it wants to have write permission. Now driver set::
>
> - range->default_flags = (1 << 63);
> - range->pfn_flags_mask = (1 << 62);
> - range->pfns[index_of_write] = (1 << 62);
> + range->default_flags = HMM_PFN_REQ_VALID;
HMM_PFN_REQ_FAULT
Regards,
Felix
> + range->pfn_flags_mask = HMM_PFN_REQ_WRITE;
> + range->pfns[index_of_write] = HMM_PFN_REQ_WRITE;
>
> With this, HMM will fault in all pages with at least read (i.e., valid) and for the
> address == range->start + (index_of_write << PAGE_SHIFT) it will fault with
> write permission i.e., if the CPU pte does not have write permission set then HMM
> will call handle_mm_fault().
>
> -Note that HMM will populate the pfns array with write permission for any page
> -that is mapped with CPU write permission no matter what values are set
> -in default_flags or pfn_flags_mask.
> +After hmm_range_fault completes the flag bits are set to the current state of
> +the page tables, ie HMM_PFN_VALID | HMM_PFN_WRITE will be set if the page is
> +writable.
>
>
> Represent and manage device memory from core kernel point of view
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 449083f9f8a2bf..bcfa8c26647d5e 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -766,17 +766,6 @@ struct amdgpu_ttm_tt {
> };
>
> #ifdef CONFIG_DRM_AMDGPU_USERPTR
> -/* flags used by HMM internal, not related to CPU/GPU PTE flags */
> -static const uint64_t hmm_range_flags[HMM_PFN_FLAG_MAX] = {
> - (1 << 0), /* HMM_PFN_VALID */
> - (1 << 1), /* HMM_PFN_WRITE */
> -};
> -
> -static const uint64_t hmm_range_values[HMM_PFN_VALUE_MAX] = {
> - 0xfffffffffffffffeUL, /* HMM_PFN_ERROR */
> - 0, /* HMM_PFN_NONE */
> -};
> -
> /**
> * amdgpu_ttm_tt_get_user_pages - get device accessible pages that back user
> * memory and start HMM tracking CPU page table update
> @@ -815,18 +804,15 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
> goto out;
> }
> range->notifier = &bo->notifier;
> - range->flags = hmm_range_flags;
> - range->values = hmm_range_values;
> - range->pfn_shift = PAGE_SHIFT;
> range->start = bo->notifier.interval_tree.start;
> range->end = bo->notifier.interval_tree.last + 1;
> - range->default_flags = hmm_range_flags[HMM_PFN_VALID];
> + range->default_flags = HMM_PFN_REQ_FAULT;
> if (!amdgpu_ttm_tt_is_readonly(ttm))
> - range->default_flags |= range->flags[HMM_PFN_WRITE];
> + range->default_flags |= HMM_PFN_REQ_WRITE;
>
> - range->pfns = kvmalloc_array(ttm->num_pages, sizeof(*range->pfns),
> - GFP_KERNEL);
> - if (unlikely(!range->pfns)) {
> + range->hmm_pfns = kvmalloc_array(ttm->num_pages,
> + sizeof(*range->hmm_pfns), GFP_KERNEL);
> + if (unlikely(!range->hmm_pfns)) {
> r = -ENOMEM;
> goto out_free_ranges;
> }
> @@ -867,7 +853,7 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
> * the notifier_lock, and mmu_interval_read_retry() must be done first.
> */
> for (i = 0; i < ttm->num_pages; i++)
> - pages[i] = hmm_device_entry_to_page(range, range->pfns[i]);
> + pages[i] = hmm_pfn_to_page(range->hmm_pfns[i]);
>
> gtt->range = range;
> mmput(mm);
> @@ -877,7 +863,7 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
> out_unlock:
> up_read(&mm->mmap_sem);
> out_free_pfns:
> - kvfree(range->pfns);
> + kvfree(range->hmm_pfns);
> out_free_ranges:
> kfree(range);
> out:
> @@ -902,7 +888,7 @@ bool amdgpu_ttm_tt_get_user_pages_done(struct ttm_tt *ttm)
> DRM_DEBUG_DRIVER("user_pages_done 0x%llx pages 0x%lx\n",
> gtt->userptr, ttm->num_pages);
>
> - WARN_ONCE(!gtt->range || !gtt->range->pfns,
> + WARN_ONCE(!gtt->range || !gtt->range->hmm_pfns,
> "No user pages to check\n");
>
> if (gtt->range) {
> @@ -912,7 +898,7 @@ bool amdgpu_ttm_tt_get_user_pages_done(struct ttm_tt *ttm)
> */
> r = mmu_interval_read_retry(gtt->range->notifier,
> gtt->range->notifier_seq);
> - kvfree(gtt->range->pfns);
> + kvfree(gtt->range->hmm_pfns);
> kfree(gtt->range);
> gtt->range = NULL;
> }
> @@ -1003,8 +989,7 @@ static void amdgpu_ttm_tt_unpin_userptr(struct ttm_tt *ttm)
>
> for (i = 0; i < ttm->num_pages; i++) {
> if (ttm->pages[i] !=
> - hmm_device_entry_to_page(gtt->range,
> - gtt->range->pfns[i]))
> + hmm_pfn_to_page(gtt->range->hmm_pfns[i]))
> break;
> }
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> index ad89e09a0be39a..07876fb0e1d665 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
> @@ -672,27 +672,61 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
> return ret;
> }
>
> -void
> -nouveau_dmem_convert_pfn(struct nouveau_drm *drm,
> - struct hmm_range *range)
> +void nouveau_hmm_convert_pfn(struct nouveau_drm *drm, struct hmm_range *range,
> + u64 *ioctl_addr)
> {
> unsigned long i, npages;
>
> + /*
> + * The ioctl_addr prepared here is passed through nvif_object_ioctl()
> + * to an eventual DMA map on some call chain like:
> + * nouveau_svm_fault():
> + * args.i.m.method = NVIF_VMM_V0_PFNMAP
> + * nouveau_range_fault()
> + * nvif_object_ioctl()
> + * client->driver->ioctl()
> + * struct nvif_driver nvif_driver_nvkm:
> + * .ioctl = nvkm_client_ioctl
> + * nvkm_ioctl()
> + * nvkm_ioctl_path()
> + * nvkm_ioctl_v0[type].func(..)
> + * nvkm_ioctl_mthd()
> + * nvkm_object_mthd()
> + * struct nvkm_object_func nvkm_uvmm:
> + * .mthd = nvkm_uvmm_mthd
> + * nvkm_uvmm_mthd()
> + * nvkm_uvmm_mthd_pfnmap()
> + * nvkm_vmm_pfn_map()
> + * nvkm_vmm_ptes_get_map()
> + * func == gp100_vmm_pgt_pfn
> + * struct nvkm_vmm_desc_func gp100_vmm_desc_spt:
> + * .pfn = gp100_vmm_pgt_pfn
> + * nvkm_vmm_iter()
> + * REF_PTES == func == gp100_vmm_pgt_pfn()
> + * dma_map_page()
> + *
> + * This is all just encoding the internal hmm reprensetation into a
> + * different nouveau internal representation.
> + */
> npages = (range->end - range->start) >> PAGE_SHIFT;
> for (i = 0; i < npages; ++i) {
> struct page *page;
> - uint64_t addr;
>
> - page = hmm_device_entry_to_page(range, range->pfns[i]);
> - if (page == NULL)
> - continue;
> -
> - if (!is_device_private_page(page))
> + if (!(range->hmm_pfns[i] & HMM_PFN_VALID)) {
> + ioctl_addr[i] = 0;
> continue;
> + }
>
> - addr = nouveau_dmem_page_addr(page);
> - range->pfns[i] &= ((1UL << range->pfn_shift) - 1);
> - range->pfns[i] |= (addr >> PAGE_SHIFT) << range->pfn_shift;
> - range->pfns[i] |= NVIF_VMM_PFNMAP_V0_VRAM;
> + page = hmm_pfn_to_page(range->hmm_pfns[i]);
> + if (is_device_private_page(page))
> + ioctl_addr[i] = nouveau_dmem_page_addr(page) |
> + NVIF_VMM_PFNMAP_V0_V |
> + NVIF_VMM_PFNMAP_V0_VRAM;
> + else
> + ioctl_addr[i] = page_to_phys(page) |
> + NVIF_VMM_PFNMAP_V0_V |
> + NVIF_VMM_PFNMAP_V0_HOST;
> + if (range->hmm_pfns[i] & HMM_PFN_WRITE)
> + ioctl_addr[i] |= NVIF_VMM_PFNMAP_V0_W;
> }
> }
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.h b/drivers/gpu/drm/nouveau/nouveau_dmem.h
> index 92394be5d64923..4607c0be7dd062 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dmem.h
> +++ b/drivers/gpu/drm/nouveau/nouveau_dmem.h
> @@ -38,8 +38,8 @@ int nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
> unsigned long start,
> unsigned long end);
>
> -void nouveau_dmem_convert_pfn(struct nouveau_drm *drm,
> - struct hmm_range *range);
> +void nouveau_hmm_convert_pfn(struct nouveau_drm *drm, struct hmm_range *range,
> + u64 *ioctl_addr);
> #else /* IS_ENABLED(CONFIG_DRM_NOUVEAU_SVM) */
> static inline void nouveau_dmem_init(struct nouveau_drm *drm) {}
> static inline void nouveau_dmem_fini(struct nouveau_drm *drm) {}
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index cf0d9bd61bebf9..d1059bce091192 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -369,18 +369,6 @@ nouveau_svmm_init(struct drm_device *dev, void *data,
> return ret;
> }
>
> -static const u64
> -nouveau_svm_pfn_flags[HMM_PFN_FLAG_MAX] = {
> - [HMM_PFN_VALID ] = NVIF_VMM_PFNMAP_V0_V,
> - [HMM_PFN_WRITE ] = NVIF_VMM_PFNMAP_V0_W,
> -};
> -
> -static const u64
> -nouveau_svm_pfn_values[HMM_PFN_VALUE_MAX] = {
> - [HMM_PFN_ERROR ] = ~NVIF_VMM_PFNMAP_V0_V,
> - [HMM_PFN_NONE ] = NVIF_VMM_PFNMAP_V0_NONE,
> -};
> -
> /* Issue fault replay for GPU to retry accesses that faulted previously. */
> static void
> nouveau_svm_fault_replay(struct nouveau_svm *svm)
> @@ -520,7 +508,8 @@ static const struct mmu_interval_notifier_ops nouveau_svm_mni_ops = {
>
> static int nouveau_range_fault(struct nouveau_svmm *svmm,
> struct nouveau_drm *drm, void *data, u32 size,
> - u64 *pfns, struct svm_notifier *notifier)
> + unsigned long hmm_pfns[], u64 *ioctl_addr,
> + struct svm_notifier *notifier)
> {
> unsigned long timeout =
> jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> @@ -529,10 +518,8 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
> .notifier = ¬ifier->notifier,
> .start = notifier->notifier.interval_tree.start,
> .end = notifier->notifier.interval_tree.last + 1,
> - .pfns = pfns,
> - .flags = nouveau_svm_pfn_flags,
> - .values = nouveau_svm_pfn_values,
> - .pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT,
> + .pfn_flags_mask = HMM_PFN_REQ_FAULT | HMM_PFN_REQ_WRITE,
> + .hmm_pfns = hmm_pfns,
> };
> struct mm_struct *mm = notifier->notifier.mm;
> int ret;
> @@ -542,12 +529,15 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
> return -EBUSY;
>
> range.notifier_seq = mmu_interval_read_begin(range.notifier);
> - range.default_flags = 0;
> - range.pfn_flags_mask = -1UL;
> down_read(&mm->mmap_sem);
> ret = hmm_range_fault(&range);
> up_read(&mm->mmap_sem);
> if (ret) {
> + /*
> + * FIXME: the input PFN_REQ flags are destroyed on
> + * -EBUSY, we need to regenerate them, also for the
> + * other continue below
> + */
> if (ret == -EBUSY)
> continue;
> return ret;
> @@ -562,7 +552,7 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
> break;
> }
>
> - nouveau_dmem_convert_pfn(drm, &range);
> + nouveau_hmm_convert_pfn(drm, &range, ioctl_addr);
>
> svmm->vmm->vmm.object.client->super = true;
> ret = nvif_object_ioctl(&svmm->vmm->vmm.object, data, size, NULL);
> @@ -589,6 +579,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
> } i;
> u64 phys[16];
> } args;
> + unsigned long hmm_pfns[ARRAY_SIZE(args.phys)];
> struct vm_area_struct *vma;
> u64 inst, start, limit;
> int fi, fn, pi, fill;
> @@ -704,12 +695,17 @@ nouveau_svm_fault(struct nvif_notify *notify)
> * access flags.
> *XXX: atomic?
> */
> - if (buffer->fault[fn]->access != 0 /* READ. */ &&
> - buffer->fault[fn]->access != 3 /* PREFETCH. */) {
> - args.phys[pi++] = NVIF_VMM_PFNMAP_V0_V |
> - NVIF_VMM_PFNMAP_V0_W;
> - } else {
> - args.phys[pi++] = NVIF_VMM_PFNMAP_V0_V;
> + switch (buffer->fault[fn]->access) {
> + case 0: /* READ. */
> + hmm_pfns[pi++] = HMM_PFN_REQ_FAULT;
> + break;
> + case 3: /* PREFETCH. */
> + hmm_pfns[pi++] = 0;
> + break;
> + default:
> + hmm_pfns[pi++] = HMM_PFN_REQ_FAULT |
> + HMM_PFN_REQ_WRITE;
> + break;
> }
> args.i.p.size = pi << PAGE_SHIFT;
>
> @@ -737,7 +733,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
> fill = (buffer->fault[fn ]->addr -
> buffer->fault[fn - 1]->addr) >> PAGE_SHIFT;
> while (--fill)
> - args.phys[pi++] = NVIF_VMM_PFNMAP_V0_NONE;
> + hmm_pfns[pi++] = 0;
> }
>
> SVMM_DBG(svmm, "wndw %016llx-%016llx covering %d fault(s)",
> @@ -753,7 +749,7 @@ nouveau_svm_fault(struct nvif_notify *notify)
> ret = nouveau_range_fault(
> svmm, svm->drm, &args,
> sizeof(args.i) + pi * sizeof(args.phys[0]),
> - args.phys, ¬ifier);
> + hmm_pfns, args.phys, ¬ifier);
> mmu_interval_notifier_remove(¬ifier.notifier);
> }
> mmput(mm);
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 81c302c884c0e3..e72529786f16f8 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -19,45 +19,45 @@
> #include <linux/mmu_notifier.h>
>
> /*
> - * hmm_pfn_flag_e - HMM flag enums
> + * On output:
> + * 0 - The page is faultable and a future call with
> + * HMM_PFN_REQ_FAULT could succeed.
> + * HMM_PFN_VALID - the pfn field points to a valid PFN. This PFN is at
> + * least readable. If dev_private_owner is !NULL then this could
> + * point at a DEVICE_PRIVATE page.
> + * HMM_PFN_WRITE - if the page memory can be written to (requires HMM_PFN_VALID)
> + * HMM_PFN_ERROR - accessing the pfn is impossible and the device should
> + * fail. ie poisoned memory, special pages, no vma, etc
> *
> - * Flags:
> - * HMM_PFN_VALID: pfn is valid. It has, at least, read permission.
> - * HMM_PFN_WRITE: CPU page table has write permission set
> - *
> - * The driver provides a flags array for mapping page protections to device
> - * PTE bits. If the driver valid bit for an entry is bit 3,
> - * i.e., (entry & (1 << 3)), then the driver must provide
> - * an array in hmm_range.flags with hmm_range.flags[HMM_PFN_VALID] == 1 << 3.
> - * Same logic apply to all flags. This is the same idea as vm_page_prot in vma
> - * except that this is per device driver rather than per architecture.
> + * On input:
> + * 0 - Return the current state of the page, do not fault it.
> + * HMM_PFN_REQ_FAULT - The output must have HMM_PFN_VALID or hmm_range_fault()
> + * will fail
> + * HMM_PFN_REQ_WRITE - The output must have HMM_PFN_WRITE or hmm_range_fault()
> + * will fail. Must be combined with HMM_PFN_REQ_FAULT.
> */
> -enum hmm_pfn_flag_e {
> - HMM_PFN_VALID = 0,
> - HMM_PFN_WRITE,
> - HMM_PFN_FLAG_MAX
> +enum hmm_pfn_flags {
> + HMM_PFN_VALID = 1UL << (BITS_PER_LONG - 1),
> + HMM_PFN_WRITE = 1UL << (BITS_PER_LONG - 2),
> + HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
> +
> + HMM_PFN_REQ_FAULT = HMM_PFN_VALID,
> + HMM_PFN_REQ_WRITE = HMM_PFN_WRITE,
> +
> + HMM_PFN_FLAGS = HMM_PFN_VALID | HMM_PFN_WRITE | HMM_PFN_ERROR,
> };
>
> /*
> - * hmm_pfn_value_e - HMM pfn special value
> - *
> - * Flags:
> - * HMM_PFN_ERROR: corresponding CPU page table entry points to poisoned memory
> - * HMM_PFN_NONE: corresponding CPU page table entry is pte_none()
> + * hmm_pfn_to_page() - return struct page pointed to by a device entry
> *
> - * Driver provides values for none entry, error entry, and special entry.
> - * Driver can alias (i.e., use same value) error and special, but
> - * it should not alias none with error or special.
> - *
> - * HMM pfn value returned by hmm_vma_get_pfns() or hmm_vma_fault() will be:
> - * hmm_range.values[HMM_PFN_ERROR] if CPU page table entry is poisonous,
> - * hmm_range.values[HMM_PFN_NONE] if there is no CPU page table entry,
> + * This must be called under the caller 'user_lock' after a successful
> + * mmu_interval_read_begin(). The caller must have tested for HMM_PFN_VALID
> + * already.
> */
> -enum hmm_pfn_value_e {
> - HMM_PFN_ERROR,
> - HMM_PFN_NONE,
> - HMM_PFN_VALUE_MAX
> -};
> +static inline struct page *hmm_pfn_to_page(unsigned long hmm_pfn)
> +{
> + return pfn_to_page(hmm_pfn & ~HMM_PFN_FLAGS);
> +}
>
> /*
> * struct hmm_range - track invalidation lock on virtual address range
> @@ -66,12 +66,9 @@ enum hmm_pfn_value_e {
> * @notifier_seq: result of mmu_interval_read_begin()
> * @start: range virtual start address (inclusive)
> * @end: range virtual end address (exclusive)
> - * @pfns: array of pfns (big enough for the range)
> - * @flags: pfn flags to match device driver page table
> - * @values: pfn value for some special case (none, special, error, ...)
> + * @hmm_pfns: array of pfns (big enough for the range)
> * @default_flags: default flags for the range (write, read, ... see hmm doc)
> * @pfn_flags_mask: allows to mask pfn flags so that only default_flags matter
> - * @pfn_shift: pfn shift value (should be <= PAGE_SHIFT)
> * @dev_private_owner: owner of device private pages
> */
> struct hmm_range {
> @@ -79,36 +76,12 @@ struct hmm_range {
> unsigned long notifier_seq;
> unsigned long start;
> unsigned long end;
> - uint64_t *pfns;
> - const uint64_t *flags;
> - const uint64_t *values;
> - uint64_t default_flags;
> - uint64_t pfn_flags_mask;
> - uint8_t pfn_shift;
> + unsigned long *hmm_pfns;
> + unsigned long default_flags;
> + unsigned long pfn_flags_mask;
> void *dev_private_owner;
> };
>
> -/*
> - * hmm_device_entry_to_page() - return struct page pointed to by a device entry
> - * @range: range use to decode device entry value
> - * @entry: device entry value to get corresponding struct page from
> - * Return: struct page pointer if entry is a valid, NULL otherwise
> - *
> - * If the device entry is valid (ie valid flag set) then return the struct page
> - * matching the entry value. Otherwise return NULL.
> - */
> -static inline struct page *hmm_device_entry_to_page(const struct hmm_range *range,
> - uint64_t entry)
> -{
> - if (entry == range->values[HMM_PFN_NONE])
> - return NULL;
> - if (entry == range->values[HMM_PFN_ERROR])
> - return NULL;
> - if (!(entry & range->flags[HMM_PFN_VALID]))
> - return NULL;
> - return pfn_to_page(entry >> range->pfn_shift);
> -}
> -
> /*
> * Please see Documentation/vm/hmm.rst for how to use the range API.
> */
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 2693393dc14b30..c1c96d4cc0554c 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -37,28 +37,13 @@ enum {
> HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT,
> };
>
> -/*
> - * hmm_device_entry_from_pfn() - create a valid device entry value from pfn
> - * @range: range use to encode HMM pfn value
> - * @pfn: pfn value for which to create the device entry
> - * Return: valid device entry for the pfn
> - */
> -static uint64_t hmm_device_entry_from_pfn(const struct hmm_range *range,
> - unsigned long pfn)
> -{
> - return (pfn << range->pfn_shift) | range->flags[HMM_PFN_VALID];
> -}
> -
> static int hmm_pfns_fill(unsigned long addr, unsigned long end,
> - struct hmm_range *range, enum hmm_pfn_value_e value)
> + struct hmm_range *range, unsigned long cpu_flags)
> {
> - uint64_t *pfns = range->pfns;
> - unsigned long i;
> + unsigned long i = (addr - range->start) >> PAGE_SHIFT;
>
> - i = (addr - range->start) >> PAGE_SHIFT;
> for (; addr < end; addr += PAGE_SIZE, i++)
> - pfns[i] = range->values[value];
> -
> + range->hmm_pfns[i] = cpu_flags;
> return 0;
> }
>
> @@ -96,7 +81,8 @@ static int hmm_vma_fault(unsigned long addr, unsigned long end,
> }
>
> static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
> - uint64_t pfns, uint64_t cpu_flags)
> + unsigned long pfn_req_flags,
> + unsigned long cpu_flags)
> {
> struct hmm_range *range = hmm_vma_walk->range;
>
> @@ -110,27 +96,28 @@ static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
> * waste to have the user pre-fill the pfn arrays with a default
> * flags value.
> */
> - pfns = (pfns & range->pfn_flags_mask) | range->default_flags;
> + pfn_req_flags &= range->pfn_flags_mask;
> + pfn_req_flags |= range->default_flags;
>
> /* We aren't ask to do anything ... */
> - if (!(pfns & range->flags[HMM_PFN_VALID]))
> + if (!(pfn_req_flags & HMM_PFN_REQ_FAULT))
> return 0;
>
> /* Need to write fault ? */
> - if ((pfns & range->flags[HMM_PFN_WRITE]) &&
> - !(cpu_flags & range->flags[HMM_PFN_WRITE]))
> + if ((pfn_req_flags & HMM_PFN_REQ_WRITE) &&
> + !(cpu_flags & HMM_PFN_WRITE))
> return HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT;
>
> /* If CPU page table is not valid then we need to fault */
> - if (!(cpu_flags & range->flags[HMM_PFN_VALID]))
> + if (!(cpu_flags & HMM_PFN_VALID))
> return HMM_NEED_FAULT;
> return 0;
> }
>
> static unsigned int
> hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
> - const uint64_t *pfns, unsigned long npages,
> - uint64_t cpu_flags)
> + const unsigned long hmm_pfns[], unsigned long npages,
> + unsigned long cpu_flags)
> {
> struct hmm_range *range = hmm_vma_walk->range;
> unsigned int required_fault = 0;
> @@ -142,12 +129,12 @@ hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
> * hmm_pte_need_fault() will always return 0.
> */
> if (!((range->default_flags | range->pfn_flags_mask) &
> - range->flags[HMM_PFN_VALID]))
> + HMM_PFN_REQ_FAULT))
> return 0;
>
> for (i = 0; i < npages; ++i) {
> - required_fault |=
> - hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags);
> + required_fault |= hmm_pte_need_fault(hmm_vma_walk, hmm_pfns[i],
> + cpu_flags);
> if (required_fault == HMM_NEED_ALL_BITS)
> return required_fault;
> }
> @@ -161,12 +148,13 @@ static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
> struct hmm_range *range = hmm_vma_walk->range;
> unsigned int required_fault;
> unsigned long i, npages;
> - uint64_t *pfns;
> + unsigned long *hmm_pfns;
>
> i = (addr - range->start) >> PAGE_SHIFT;
> npages = (end - addr) >> PAGE_SHIFT;
> - pfns = &range->pfns[i];
> - required_fault = hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0);
> + hmm_pfns = &range->hmm_pfns[i];
> + required_fault =
> + hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0);
> if (!walk->vma) {
> if (required_fault)
> return -EFAULT;
> @@ -174,44 +162,44 @@ static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
> }
> if (required_fault)
> return hmm_vma_fault(addr, end, required_fault, walk);
> - return hmm_pfns_fill(addr, end, range, HMM_PFN_NONE);
> + return hmm_pfns_fill(addr, end, range, 0);
> }
>
> -static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
> +static inline unsigned long pmd_to_hmm_pfn_flags(struct hmm_range *range,
> + pmd_t pmd)
> {
> if (pmd_protnone(pmd))
> return 0;
> - return pmd_write(pmd) ? range->flags[HMM_PFN_VALID] |
> - range->flags[HMM_PFN_WRITE] :
> - range->flags[HMM_PFN_VALID];
> + return pmd_write(pmd) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
> - unsigned long end, uint64_t *pfns, pmd_t pmd)
> + unsigned long end, unsigned long hmm_pfns[],
> + pmd_t pmd)
> {
> struct hmm_vma_walk *hmm_vma_walk = walk->private;
> struct hmm_range *range = hmm_vma_walk->range;
> unsigned long pfn, npages, i;
> unsigned int required_fault;
> - uint64_t cpu_flags;
> + unsigned long cpu_flags;
>
> npages = (end - addr) >> PAGE_SHIFT;
> cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
> required_fault =
> - hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags);
> + hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, cpu_flags);
> if (required_fault)
> return hmm_vma_fault(addr, end, required_fault, walk);
>
> pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
> - pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags;
> + hmm_pfns[i] = pfn | cpu_flags;
> return 0;
> }
> #else /* CONFIG_TRANSPARENT_HUGEPAGE */
> /* stub to allow the code below to compile */
> int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
> - unsigned long end, uint64_t *pfns, pmd_t pmd);
> + unsigned long end, unsigned long hmm_pfns[], pmd_t pmd);
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> static inline bool hmm_is_device_private_entry(struct hmm_range *range,
> @@ -222,31 +210,31 @@ static inline bool hmm_is_device_private_entry(struct hmm_range *range,
> range->dev_private_owner;
> }
>
> -static inline uint64_t pte_to_hmm_pfn_flags(struct hmm_range *range, pte_t pte)
> +static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range,
> + pte_t pte)
> {
> if (pte_none(pte) || !pte_present(pte) || pte_protnone(pte))
> return 0;
> - return pte_write(pte) ? range->flags[HMM_PFN_VALID] |
> - range->flags[HMM_PFN_WRITE] :
> - range->flags[HMM_PFN_VALID];
> + return pte_write(pte) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
> }
>
> static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
> unsigned long end, pmd_t *pmdp, pte_t *ptep,
> - uint64_t *pfn)
> + unsigned long *hmm_pfn)
> {
> struct hmm_vma_walk *hmm_vma_walk = walk->private;
> struct hmm_range *range = hmm_vma_walk->range;
> unsigned int required_fault;
> - uint64_t cpu_flags;
> + unsigned long cpu_flags;
> pte_t pte = *ptep;
> - uint64_t orig_pfn = *pfn;
> + uint64_t pfn_req_flags = *hmm_pfn;
>
> if (pte_none(pte)) {
> - required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
> + required_fault =
> + hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
> if (required_fault)
> goto fault;
> - *pfn = range->values[HMM_PFN_NONE];
> + *hmm_pfn = 0;
> return 0;
> }
>
> @@ -258,17 +246,18 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
> * the PFN even if not present.
> */
> if (hmm_is_device_private_entry(range, entry)) {
> - *pfn = hmm_device_entry_from_pfn(range,
> - device_private_entry_to_pfn(entry));
> - *pfn |= range->flags[HMM_PFN_VALID];
> + cpu_flags = HMM_PFN_VALID;
> if (is_write_device_private_entry(entry))
> - *pfn |= range->flags[HMM_PFN_WRITE];
> + cpu_flags |= HMM_PFN_WRITE;
> + *hmm_pfn = device_private_entry_to_pfn(entry) |
> + cpu_flags;
> return 0;
> }
>
> - required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
> + required_fault =
> + hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
> if (!required_fault) {
> - *pfn = range->values[HMM_PFN_NONE];
> + *hmm_pfn = 0;
> return 0;
> }
>
> @@ -288,7 +277,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
> }
>
> cpu_flags = pte_to_hmm_pfn_flags(range, pte);
> - required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags);
> + required_fault =
> + hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
> if (required_fault)
> goto fault;
>
> @@ -297,15 +287,15 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
> * fall through and treat it like a normal page.
> */
> if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
> - if (hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0)) {
> + if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
> pte_unmap(ptep);
> return -EFAULT;
> }
> - *pfn = range->values[HMM_PFN_ERROR];
> + *hmm_pfn = HMM_PFN_ERROR;
> return 0;
> }
>
> - *pfn = hmm_device_entry_from_pfn(range, pte_pfn(pte)) | cpu_flags;
> + *hmm_pfn = pte_pfn(pte) | cpu_flags;
> return 0;
>
> fault:
> @@ -321,7 +311,8 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> {
> struct hmm_vma_walk *hmm_vma_walk = walk->private;
> struct hmm_range *range = hmm_vma_walk->range;
> - uint64_t *pfns = &range->pfns[(start - range->start) >> PAGE_SHIFT];
> + unsigned long *hmm_pfns =
> + &range->hmm_pfns[(start - range->start) >> PAGE_SHIFT];
> unsigned long npages = (end - start) >> PAGE_SHIFT;
> unsigned long addr = start;
> pte_t *ptep;
> @@ -333,16 +324,16 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> return hmm_vma_walk_hole(start, end, -1, walk);
>
> if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
> - if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0)) {
> + if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0)) {
> hmm_vma_walk->last = addr;
> pmd_migration_entry_wait(walk->mm, pmdp);
> return -EBUSY;
> }
> - return hmm_pfns_fill(start, end, range, HMM_PFN_NONE);
> + return hmm_pfns_fill(start, end, range, 0);
> }
>
> if (!pmd_present(pmd)) {
> - if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0))
> + if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
> return -EFAULT;
> return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
> }
> @@ -362,7 +353,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
> goto again;
>
> - return hmm_vma_handle_pmd(walk, addr, end, pfns, pmd);
> + return hmm_vma_handle_pmd(walk, addr, end, hmm_pfns, pmd);
> }
>
> /*
> @@ -372,16 +363,16 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> * recover.
> */
> if (pmd_bad(pmd)) {
> - if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0))
> + if (hmm_range_need_fault(hmm_vma_walk, hmm_pfns, npages, 0))
> return -EFAULT;
> return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
> }
>
> ptep = pte_offset_map(pmdp, addr);
> - for (; addr < end; addr += PAGE_SIZE, ptep++, pfns++) {
> + for (; addr < end; addr += PAGE_SIZE, ptep++, hmm_pfns++) {
> int r;
>
> - r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, pfns);
> + r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, hmm_pfns);
> if (r) {
> /* hmm_vma_handle_pte() did pte_unmap() */
> return r;
> @@ -393,13 +384,12 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
>
> #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && \
> defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
> -static inline uint64_t pud_to_hmm_pfn_flags(struct hmm_range *range, pud_t pud)
> +static inline unsigned long pud_to_hmm_pfn_flags(struct hmm_range *range,
> + pud_t pud)
> {
> if (!pud_present(pud))
> return 0;
> - return pud_write(pud) ? range->flags[HMM_PFN_VALID] |
> - range->flags[HMM_PFN_WRITE] :
> - range->flags[HMM_PFN_VALID];
> + return pud_write(pud) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
> }
>
> static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
> @@ -427,7 +417,8 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
> if (pud_huge(pud) && pud_devmap(pud)) {
> unsigned long i, npages, pfn;
> unsigned int required_fault;
> - uint64_t *pfns, cpu_flags;
> + unsigned long *hmm_pfns;
> + unsigned long cpu_flags;
>
> if (!pud_present(pud)) {
> spin_unlock(ptl);
> @@ -436,10 +427,10 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
>
> i = (addr - range->start) >> PAGE_SHIFT;
> npages = (end - addr) >> PAGE_SHIFT;
> - pfns = &range->pfns[i];
> + hmm_pfns = &range->hmm_pfns[i];
>
> cpu_flags = pud_to_hmm_pfn_flags(range, pud);
> - required_fault = hmm_range_need_fault(hmm_vma_walk, pfns,
> + required_fault = hmm_range_need_fault(hmm_vma_walk, hmm_pfns,
> npages, cpu_flags);
> if (required_fault) {
> spin_unlock(ptl);
> @@ -448,8 +439,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
>
> pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
> for (i = 0; i < npages; ++i, ++pfn)
> - pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
> - cpu_flags;
> + hmm_pfns[i] = pfn | cpu_flags;
> goto out_unlock;
> }
>
> @@ -473,8 +463,9 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
> struct hmm_vma_walk *hmm_vma_walk = walk->private;
> struct hmm_range *range = hmm_vma_walk->range;
> struct vm_area_struct *vma = walk->vma;
> - uint64_t orig_pfn, cpu_flags;
> unsigned int required_fault;
> + unsigned long pfn_req_flags;
> + unsigned long cpu_flags;
> spinlock_t *ptl;
> pte_t entry;
>
> @@ -482,9 +473,10 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
> entry = huge_ptep_get(pte);
>
> i = (start - range->start) >> PAGE_SHIFT;
> - orig_pfn = range->pfns[i];
> + pfn_req_flags = range->hmm_pfns[i];
> cpu_flags = pte_to_hmm_pfn_flags(range, entry);
> - required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags);
> + required_fault =
> + hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, cpu_flags);
> if (required_fault) {
> spin_unlock(ptl);
> return hmm_vma_fault(addr, end, required_fault, walk);
> @@ -492,8 +484,8 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>
> pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
> for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
> - range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
> - cpu_flags;
> + range->hmm_pfns[i] = pfn | cpu_flags;
> +
> spin_unlock(ptl);
> return 0;
> }
> @@ -524,7 +516,7 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
> * failure.
> */
> if (hmm_range_need_fault(hmm_vma_walk,
> - range->pfns +
> + range->hmm_pfns +
> ((start - range->start) >> PAGE_SHIFT),
> (end - start) >> PAGE_SHIFT, 0))
> return -EFAULT;
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