From: Jason Gunthorpe jgg@mellanox.com

Using two bools instead of flags return is not necessary and leads to bugs. Returning a value is easier for the compiler to check and easier to pass around the code flow.

Convert the two bools into flags and push the change to all callers.

Signed-off-by: Jason Gunthorpe jgg@mellanox.com --- mm/hmm.c | 153 ++++++++++++++++++++++++------------------------------- 1 file changed, 67 insertions(+), 86 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c index 3a2610e0713329..b4f662eadb7a7c 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -32,6 +32,11 @@ struct hmm_vma_walk { unsigned int flags; };

+enum { + NEED_FAULT = 1 << 0, + NEED_WRITE_FAULT = 1 << 1, +}; + static int hmm_pfns_fill(unsigned long addr, unsigned long end, struct hmm_range *range, enum hmm_pfn_value_e value) { @@ -49,8 +54,7 @@ static int hmm_pfns_fill(unsigned long addr, unsigned long end, * hmm_vma_fault() - fault in a range lacking valid pmd or pte(s) * @addr: range virtual start address (inclusive) * @end: range virtual end address (exclusive) - * @fault: should we fault or not ? - * @write_fault: write fault ? + * @required_fault: NEED_FAULT_* flags * @walk: mm_walk structure * Return: -EBUSY after page fault, or page fault error * @@ -58,8 +62,7 @@ static int hmm_pfns_fill(unsigned long addr, unsigned long end, * or whenever there is no page directory covering the virtual address range. */ static int hmm_vma_fault(unsigned long addr, unsigned long end, - bool fault, bool write_fault, - struct mm_walk *walk) + unsigned int required_fault, struct mm_walk *walk) { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; @@ -68,13 +71,13 @@ static int hmm_vma_fault(unsigned long addr, unsigned long end, unsigned long i = (addr - range->start) >> PAGE_SHIFT; unsigned int fault_flags = FAULT_FLAG_REMOTE;

- WARN_ON_ONCE(!fault && !write_fault); + WARN_ON_ONCE(!required_fault); hmm_vma_walk->last = addr;

if (!vma) goto out_error;

- if (write_fault) { + if (required_fault & NEED_WRITE_FAULT) { if (!(vma->vm_flags & VM_WRITE)) return -EPERM; fault_flags |= FAULT_FLAG_WRITE; @@ -91,14 +94,13 @@ static int hmm_vma_fault(unsigned long addr, unsigned long end, return -EFAULT; }

-static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, - uint64_t pfns, uint64_t cpu_flags, - bool *fault, bool *write_fault) +static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, + uint64_t pfns, uint64_t cpu_flags) { struct hmm_range *range = hmm_vma_walk->range;

if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) - return; + return 0;

/* * So we not only consider the individual per page request we also @@ -114,37 +116,37 @@ static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,

/* We aren't ask to do anything ... */ if (!(pfns & range->flags[HMM_PFN_VALID])) - return; + return 0;

- /* If CPU page table is not valid then we need to fault */ - *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]); /* Need to write fault ? */ if ((pfns & range->flags[HMM_PFN_WRITE]) && - !(cpu_flags & range->flags[HMM_PFN_WRITE])) { - *write_fault = true; - *fault = true; - } + !(cpu_flags & range->flags[HMM_PFN_WRITE])) + return NEED_FAULT | NEED_WRITE_FAULT; + + /* If CPU page table is not valid then we need to fault */ + if (!(cpu_flags & range->flags[HMM_PFN_VALID])) + return NEED_FAULT; + return 0; }

-static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk, - const uint64_t *pfns, unsigned long npages, - uint64_t cpu_flags, bool *fault, - bool *write_fault) +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) { + unsigned int required_fault = 0; unsigned long i;

- if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) { - *fault = *write_fault = false; - return; - } + if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) + return 0;

- *fault = *write_fault = false; for (i = 0; i < npages; ++i) { - hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags, - fault, write_fault); - if ((*write_fault)) - return; + required_fault |= + hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags); + if (required_fault == (NEED_FAULT | NEED_WRITE_FAULT)) + return required_fault; } + return required_fault; }

static int hmm_vma_walk_hole(unsigned long addr, unsigned long end, @@ -152,17 +154,16 @@ static int hmm_vma_walk_hole(unsigned long addr, unsigned long end, { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; - bool fault, write_fault; + unsigned int required_fault; unsigned long i, npages; uint64_t *pfns;

i = (addr - range->start) >> PAGE_SHIFT; npages = (end - addr) >> PAGE_SHIFT; pfns = &range->pfns[i]; - hmm_range_need_fault(hmm_vma_walk, pfns, npages, - 0, &fault, &write_fault); - if (fault || write_fault) - return hmm_vma_fault(addr, end, fault, write_fault, walk); + required_fault = hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0); + if (required_fault) + return hmm_vma_fault(addr, end, required_fault, walk); hmm_vma_walk->last = addr; return hmm_pfns_fill(addr, end, range, HMM_PFN_NONE); } @@ -183,16 +184,15 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr, struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; unsigned long pfn, npages, i; - bool fault, write_fault; + unsigned int required_fault; uint64_t cpu_flags;

npages = (end - addr) >> PAGE_SHIFT; cpu_flags = pmd_to_hmm_pfn_flags(range, pmd); - hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags, - &fault, &write_fault); - - if (fault || write_fault) - return hmm_vma_fault(addr, end, fault, write_fault, walk); + required_fault = + hmm_range_need_fault(hmm_vma_walk, 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++) @@ -229,18 +229,15 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, { struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_range *range = hmm_vma_walk->range; - bool fault, write_fault; + unsigned int required_fault; uint64_t cpu_flags; pte_t pte = *ptep; uint64_t orig_pfn = *pfn;

*pfn = range->values[HMM_PFN_NONE]; - fault = write_fault = false; - if (pte_none(pte)) { - hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0, - &fault, &write_fault); - if (fault || write_fault) + required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0); + if (required_fault) goto fault; return 0; } @@ -261,9 +258,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, return 0; }

- hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0, &fault, - &write_fault); - if (!fault && !write_fault) + required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0); + if (!required_fault) return 0;

if (!non_swap_entry(entry)) @@ -283,9 +279,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, }

cpu_flags = pte_to_hmm_pfn_flags(range, pte); - hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, &fault, - &write_fault); - if (fault || write_fault) + required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags); + if (required_fault) goto fault;

/* @@ -293,9 +288,7 @@ 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))) { - hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0, &fault, - &write_fault); - if (fault || write_fault) { + if (hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0)) { pte_unmap(ptep); return -EFAULT; } @@ -309,7 +302,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, fault: pte_unmap(ptep); /* Fault any virtual address we were asked to fault */ - return hmm_vma_fault(addr, end, fault, write_fault, walk); + return hmm_vma_fault(addr, end, required_fault, walk); }

static int hmm_vma_walk_pmd(pmd_t *pmdp, @@ -322,7 +315,6 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, uint64_t *pfns = &range->pfns[(start - range->start) >> PAGE_SHIFT]; unsigned long npages = (end - start) >> PAGE_SHIFT; unsigned long addr = start; - bool fault, write_fault; pte_t *ptep; pmd_t pmd;

@@ -332,9 +324,7 @@ 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)) { - hmm_range_need_fault(hmm_vma_walk, pfns, npages, - 0, &fault, &write_fault); - if (fault || write_fault) { + if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0)) { hmm_vma_walk->last = addr; pmd_migration_entry_wait(walk->mm, pmdp); return -EBUSY; @@ -343,9 +333,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, }

if (!pmd_present(pmd)) { - hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0, &fault, - &write_fault); - if (fault || write_fault) + if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0)) return -EFAULT; return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); } @@ -375,9 +363,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, * recover. */ if (pmd_bad(pmd)) { - hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0, &fault, - &write_fault); - if (fault || write_fault) + if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0)) return -EFAULT; return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR); } @@ -434,8 +420,8 @@ 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; - bool fault, write_fault;

if (!pud_present(pud)) { spin_unlock(ptl); @@ -447,12 +433,11 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, pfns = &range->pfns[i];

cpu_flags = pud_to_hmm_pfn_flags(range, pud); - hmm_range_need_fault(hmm_vma_walk, pfns, npages, - cpu_flags, &fault, &write_fault); - if (fault || write_fault) { + required_fault = hmm_range_need_fault(hmm_vma_walk, pfns, + npages, cpu_flags); + if (required_fault) { spin_unlock(ptl); - return hmm_vma_fault(addr, end, fault, write_fault, - walk); + return hmm_vma_fault(addr, end, required_fault, walk); }

pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); @@ -484,7 +469,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask, struct hmm_range *range = hmm_vma_walk->range; struct vm_area_struct *vma = walk->vma; uint64_t orig_pfn, cpu_flags; - bool fault, write_fault; + unsigned int required_fault; spinlock_t *ptl; pte_t entry;

@@ -495,12 +480,10 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask, orig_pfn = range->pfns[i]; range->pfns[i] = range->values[HMM_PFN_NONE]; cpu_flags = pte_to_hmm_pfn_flags(range, entry); - fault = write_fault = false; - hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, - &fault, &write_fault); - if (fault || write_fault) { + required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags); + if (required_fault) { spin_unlock(ptl); - return hmm_vma_fault(addr, end, fault, write_fault, walk); + return hmm_vma_fault(addr, end, required_fault, walk); }

pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT); @@ -532,17 +515,15 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end, */ if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) || !(vma->vm_flags & VM_READ)) { - bool fault, write_fault; - /* * Check to see if a fault is requested for any page in the * range. */ - hmm_range_need_fault(hmm_vma_walk, range->pfns + - ((start - range->start) >> PAGE_SHIFT), - (end - start) >> PAGE_SHIFT, - 0, &fault, &write_fault); - if (fault || write_fault) + if (hmm_range_need_fault(hmm_vma_walk, + range->pfns + + ((start - range->start) >> + PAGE_SHIFT), + (end - start) >> PAGE_SHIFT, 0)) return -EFAULT;

hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);

From: Jason Gunthorpe jgg@mellanox.com

Now that flags are handled on a fine-grained per-page basis this global flag is redundant and has a confusing overlap with the pfn_flags_mask and default_flags.

Normalize the HMM_FAULT_SNAPSHOT behavior into one place. Callers needing the SNAPSHOT behavior should set a pfn_flags_mask and default_flags that always results in a cleared HMM_PFN_REQ_FAULT. Then no pages will be faulted, and HMM_FAULT_SNAPSHOT is not a special flow that overrides the masking mechanism.

As this is the last flag, also remove the flags argument. If future flags are needed they can be part of the struct hmm_range function arguments.

Signed-off-by: Jason Gunthorpe jgg@mellanox.com --- Documentation/vm/hmm.rst | 12 +++++------- drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +- drivers/gpu/drm/nouveau/nouveau_svm.c | 2 +- include/linux/hmm.h | 5 +---- mm/hmm.c | 17 +++++++++-------- 5 files changed, 17 insertions(+), 21 deletions(-)

diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 95fec596836262..4e3e9362afeb10 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -161,13 +161,11 @@ device must complete the update before the driver callback returns. When the device driver wants to populate a range of virtual addresses, it can use::

- long hmm_range_fault(struct hmm_range *range, unsigned int flags); + long hmm_range_fault(struct hmm_range *range);

-With the HMM_RANGE_SNAPSHOT flag, it will only fetch present CPU page table -entries and will not trigger a page fault on missing or non-present entries. -Without that flag, it does trigger a page fault on missing or read-only entries -if write access is requested (see below). Page faults use the generic mm page -fault code path just like a CPU page fault. +It will trigger a page fault on missing or read-only entries if write access is +requested (see below). Page faults use the generic mm page fault code path just +like a CPU page fault.

Both functions copy CPU page table entries into their pfns array argument. Each entry in that array corresponds to an address in the virtual range. HMM @@ -197,7 +195,7 @@ The usage pattern is:: again: range.notifier_seq = mmu_interval_read_begin(&interval_sub); down_read(&mm->mmap_sem); - ret = hmm_range_fault(&range, HMM_RANGE_SNAPSHOT); + ret = hmm_range_fault(&range); if (ret) { up_read(&mm->mmap_sem); if (ret == -EBUSY) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index 90821ce5e6cad0..c520290709371b 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -856,7 +856,7 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages) range->notifier_seq = mmu_interval_read_begin(&bo->notifier);

down_read(&mm->mmap_sem); - r = hmm_range_fault(range, 0); + r = hmm_range_fault(range); up_read(&mm->mmap_sem); if (unlikely(r <= 0)) { /* diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c index 39c731a99937c6..e3797b2d4d1759 100644 --- a/drivers/gpu/drm/nouveau/nouveau_svm.c +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c @@ -540,7 +540,7 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm, range.default_flags = 0; range.pfn_flags_mask = -1UL; down_read(&mm->mmap_sem); - ret = hmm_range_fault(&range, 0); + ret = hmm_range_fault(&range); up_read(&mm->mmap_sem); if (ret <= 0) { if (ret == 0 || ret == -EBUSY) diff --git a/include/linux/hmm.h b/include/linux/hmm.h index 184a8633260f9d..6b4004905aac89 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -167,13 +167,10 @@ static inline struct page *hmm_device_entry_to_page(const struct hmm_range *rang return pfn_to_page(entry >> range->pfn_shift); }

-/* Don't fault in missing PTEs, just snapshot the current state. */ -#define HMM_FAULT_SNAPSHOT (1 << 1) - /* * Please see Documentation/vm/hmm.rst for how to use the range API. */ -long hmm_range_fault(struct hmm_range *range, unsigned int flags); +long hmm_range_fault(struct hmm_range *range);

/* * HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range diff --git a/mm/hmm.c b/mm/hmm.c index 687d21c675ee60..7f77fb6e35cf78 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -29,7 +29,6 @@ struct hmm_vma_walk { struct hmm_range *range; unsigned long last; - unsigned int flags; };

enum { @@ -111,9 +110,6 @@ static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, { struct hmm_range *range = hmm_vma_walk->range;

- if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) - return 0; - /* * So we not only consider the individual per page request we also * consider the default flags requested for the range. The API can @@ -146,10 +142,17 @@ hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk, const uint64_t *pfns, unsigned long npages, uint64_t cpu_flags) { + struct hmm_range *range = hmm_vma_walk->range; unsigned int required_fault = 0; unsigned long i;

- if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) + /* + * If there is no way for valid to be set in hmm_pte_need_fault() then + * don't bother to call it. + */ + if (!(((range->flags[HMM_PFN_VALID] & range->pfn_flags_mask) | + range->default_flags) & + range->flags[HMM_PFN_VALID])) return 0;

for (i = 0; i < npages; ++i) { @@ -559,7 +562,6 @@ static const struct mm_walk_ops hmm_walk_ops = { /** * hmm_range_fault - try to fault some address in a virtual address range * @range: range being faulted - * @flags: HMM_FAULT_* flags * * Return: the number of valid pages in range->pfns[] (from range start * address), which may be zero. On error one of the following status codes @@ -583,12 +585,11 @@ static const struct mm_walk_ops hmm_walk_ops = { * On error, for one virtual address in the range, the function will mark the * corresponding HMM pfn entry with an error flag. */ -long hmm_range_fault(struct hmm_range *range, unsigned int flags) +long hmm_range_fault(struct hmm_range *range) { struct hmm_vma_walk hmm_vma_walk = { .range = range, .last = range->start, - .flags = flags, }; struct mm_struct *mm = range->notifier->mm; int ret;

From: Jason Gunthorpe jgg@mellanox.com

swp_offset() should not be called directly, the wrappers are supposed to abstract away the encoding of the device_private specific information in the swap entry.

Signed-off-by: Jason Gunthorpe jgg@mellanox.com --- mm/hmm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c index a09b4908e9c81a..fd9ee2b5fd9989 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -259,8 +259,8 @@ 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, - swp_offset(entry)); + *pfn = hmm_device_entry_from_pfn( + range, device_private_entry_to_pfn(entry)); *pfn |= range->flags[HMM_PFN_VALID]; if (is_write_device_private_entry(entry)) *pfn |= range->flags[HMM_PFN_WRITE];