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drm/ttm, drm/vmwgfx: Support huge TTM pagefaults 

Support huge (PMD-size and PUD-size) page-table entries by providing a
huge_fault() callback.
We still support private mappings and write-notify by splitting the huge
page-table entries on write-access.

Note that for huge page-faults to occur, either the kernel needs to be
compiled with trans-huge-pages always enabled, or the kernel needs to be
compiled with trans-huge-pages enabled using madvise, and the user-space
app needs to call madvise() to enable trans-huge pages on a per-mapping
basis.

Furthermore huge page-faults will not succeed unless buffer objects and
user-space addresses are aligned on huge page size boundaries.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Hellstrom (VMware) <thomas_os@shipmail.org>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
This commit is contained in:
Thomas Hellstrom (VMware) 2020-03-24 18:48:33 +01:00
parent 9a9731b18c
commit 314b6580ad
3 changed files with 161 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

161
drivers/gpu/drm/ttm/ttm_bo_vm.c
View File

@ -156,6 +156,89 @@ vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
}
EXPORT_SYMBOL(ttm_bo_vm_reserve);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/**
* ttm_bo_vm_insert_huge - Insert a pfn for PUD or PMD faults
* @vmf: Fault data
* @bo: The buffer object
* @page_offset: Page offset from bo start
* @fault_page_size: The size of the fault in pages.
* @pgprot: The page protections.
* Does additional checking whether it's possible to insert a PUD or PMD
* pfn and performs the insertion.
*
* Return: VM_FAULT_NOPAGE on successful insertion, VM_FAULT_FALLBACK if
* a huge fault was not possible, or on insertion error.
*/
static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
struct ttm_buffer_object *bo,
pgoff_t page_offset,
pgoff_t fault_page_size,
pgprot_t pgprot)
{
pgoff_t i;
vm_fault_t ret;
unsigned long pfn;
pfn_t pfnt;
struct ttm_tt *ttm = bo->ttm;
bool write = vmf->flags & FAULT_FLAG_WRITE;
/* Fault should not cross bo boundary. */
page_offset &= ~(fault_page_size - 1);
if (page_offset + fault_page_size > bo->num_pages)
goto out_fallback;
if (bo->mem.bus.is_iomem)
pfn = ttm_bo_io_mem_pfn(bo, page_offset);
else
pfn = page_to_pfn(ttm->pages[page_offset]);
/* pfn must be fault_page_size aligned. */
if ((pfn & (fault_page_size - 1)) != 0)
goto out_fallback;
/* Check that memory is contiguous. */
if (!bo->mem.bus.is_iomem) {
for (i = 1; i < fault_page_size; ++i) {
if (page_to_pfn(ttm->pages[page_offset + i]) != pfn + i)
goto out_fallback;
}
} else if (bo->bdev->driver->io_mem_pfn) {
for (i = 1; i < fault_page_size; ++i) {
if (ttm_bo_io_mem_pfn(bo, page_offset + i) != pfn + i)
goto out_fallback;
}
}
pfnt = __pfn_to_pfn_t(pfn, PFN_DEV);
if (fault_page_size == (HPAGE_PMD_SIZE >> PAGE_SHIFT))
ret = vmf_insert_pfn_pmd_prot(vmf, pfnt, pgprot, write);
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
else if (fault_page_size == (HPAGE_PUD_SIZE >> PAGE_SHIFT))
ret = vmf_insert_pfn_pud_prot(vmf, pfnt, pgprot, write);
#endif
else
WARN_ON_ONCE(ret = VM_FAULT_FALLBACK);
if (ret != VM_FAULT_NOPAGE)
goto out_fallback;
return VM_FAULT_NOPAGE;
out_fallback:
count_vm_event(THP_FAULT_FALLBACK);
return VM_FAULT_FALLBACK;
}
#else
static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
struct ttm_buffer_object *bo,
pgoff_t page_offset,
pgoff_t fault_page_size,
pgprot_t pgprot)
{
return VM_FAULT_FALLBACK;
}
#endif
/**
* ttm_bo_vm_fault_reserved - TTM fault helper
* @vmf: The struct vm_fault given as argument to the fault callback
@ -163,6 +246,7 @@ EXPORT_SYMBOL(ttm_bo_vm_reserve);
* @num_prefault: Maximum number of prefault pages. The caller may want to
* specify this based on madvice settings and the size of the GPU object
* backed by the memory.
* @fault_page_size: The size of the fault in pages.
*
* This function inserts one or more page table entries pointing to the
* memory backing the buffer object, and then returns a return code
@ -176,7 +260,8 @@ EXPORT_SYMBOL(ttm_bo_vm_reserve);
*/
vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
pgprot_t prot,
pgoff_t num_prefault)
pgoff_t num_prefault,
pgoff_t fault_page_size)
{
struct vm_area_struct *vma = vmf->vma;
struct ttm_buffer_object *bo = vma->vm_private_data;
@ -268,6 +353,13 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
prot = pgprot_decrypted(prot);
}
/* We don't prefault on huge faults. Yet. */
if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && fault_page_size != 1) {
ret = ttm_bo_vm_insert_huge(vmf, bo, page_offset,
fault_page_size, prot);
goto out_io_unlock;
}
/*
* Speculatively prefault a number of pages. Only error on
* first page.
@ -334,7 +426,7 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
return ret;
prot = vma->vm_page_prot;
ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT, 1);
if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
return ret;
@ -344,6 +436,66 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
}
EXPORT_SYMBOL(ttm_bo_vm_fault);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/**
* ttm_pgprot_is_wrprotecting - Is a page protection value write-protecting?
* @prot: The page protection value
*
* Return: true if @prot is write-protecting. false otherwise.
*/
static bool ttm_pgprot_is_wrprotecting(pgprot_t prot)
{
/*
* This is meant to say "pgprot_wrprotect(prot) == prot" in a generic
* way. Unfortunately there is no generic pgprot_wrprotect.
*/
return pte_val(pte_wrprotect(__pte(pgprot_val(prot)))) ==
pgprot_val(prot);
}
static vm_fault_t ttm_bo_vm_huge_fault(struct vm_fault *vmf,
enum page_entry_size pe_size)
{
struct vm_area_struct *vma = vmf->vma;
pgprot_t prot;
struct ttm_buffer_object *bo = vma->vm_private_data;
vm_fault_t ret;
pgoff_t fault_page_size = 0;
bool write = vmf->flags & FAULT_FLAG_WRITE;
switch (pe_size) {
case PE_SIZE_PMD:
fault_page_size = HPAGE_PMD_SIZE >> PAGE_SHIFT;
break;
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
case PE_SIZE_PUD:
fault_page_size = HPAGE_PUD_SIZE >> PAGE_SHIFT;
break;
#endif
default:
WARN_ON_ONCE(1);
return VM_FAULT_FALLBACK;
}
/* Fallback on write dirty-tracking or COW */
if (write && ttm_pgprot_is_wrprotecting(vma->vm_page_prot))
return VM_FAULT_FALLBACK;
ret = ttm_bo_vm_reserve(bo, vmf);
if (ret)
return ret;
prot = vm_get_page_prot(vma->vm_flags);
ret = ttm_bo_vm_fault_reserved(vmf, prot, 1, fault_page_size);
if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
return ret;
dma_resv_unlock(bo->base.resv);
return ret;
}
#endif
void ttm_bo_vm_open(struct vm_area_struct *vma)
{
struct ttm_buffer_object *bo = vma->vm_private_data;
@ -445,7 +597,10 @@ static const struct vm_operations_struct ttm_bo_vm_ops = {
.fault = ttm_bo_vm_fault,
.open = ttm_bo_vm_open,
.close = ttm_bo_vm_close,
.access = ttm_bo_vm_access
.access = ttm_bo_vm_access,
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
.huge_fault = ttm_bo_vm_huge_fault,
#endif
};
static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,

2
drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c
View File

@ -477,7 +477,7 @@ vm_fault_t vmw_bo_vm_fault(struct vm_fault *vmf)
else
prot = vm_get_page_prot(vma->vm_flags);
ret = ttm_bo_vm_fault_reserved(vmf, prot, num_prefault);
ret = ttm_bo_vm_fault_reserved(vmf, prot, num_prefault, 1);
if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
return ret;

3
include/drm/ttm/ttm_bo_api.h
View File

@ -727,7 +727,8 @@ vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
pgprot_t prot,
pgoff_t num_prefault);
pgoff_t num_prefault,
pgoff_t fault_page_size);
vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf);