[RFC PATCH 0/3] mm modifications / helpers for emulated GPU coherent memory

[RFC PATCH 0/3] mm modifications / helpers for emulated GPU coherent memory

[Thomas Hellstrom]

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org

Hi,
This is an early RFC to make sure I don't go too far in the wrong direction.

Non-coherent GPUs that can't directly see contents in CPU-visible memory,
like VMWare's SVGA device, run into trouble when trying to implement
coherent memory requirements of modern graphics APIs. Examples are
Vulkan and OpenGL 4.4's ARB_buffer_storage.

To remedy, we need to emulate coherent memory. Typically when it's detected
that a buffer object is about to be accessed by the GPU, we need to
gather the ranges that have been dirtied by the CPU since the last operation,
apply an operation to make the content visible to the GPU and clear the
the dirty tracking.

Depending on the size of the buffer object and the access pattern there are
two major possibilities:

1) Use page_mkwrite() and pfn_mkwrite(). (GPU buffer objects are backed
either by PCI device memory or by driver-alloced pages).
The dirty-tracking needs to be reset by write-protecting the affected ptes
and flush tlb. This has a complexity of O(num_dirty_pages), but the
write page-fault is of course costly.

2) Use hardware dirty-flags in the ptes. The dirty-tracking needs to be reset
by clearing the dirty bits and flush tlb. This has a complexity of
O(num_buffer_object_pages) and dirty bits need to be scanned in full before
each gpu-access.

So in practice the two methods need to be interleaved for best performance.

So to facilitate this, I propose two new helpers, apply_as_wrprotect() and
apply_as_clean() ("as" stands for address-space) both inspired by
unmap_mapping_range(). Users of these helpers are in the making, but needs
some cleaning-up.

There's also a change to x_mkwrite() to allow dropping the mmap_sem while
waiting.

Any comments or suggestions appreciated.

Thanks,
Thomas



_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

[RFC PATCH 1/3] mm: Allow the [page|pfn]_mkwrite callbacks to drop the mmap_sem

[Thomas Hellstrom]

Driver fault callbacks are allowed to drop the mmap_sem when expecting
long hardware waits to avoid blocking other mm users. Allow the mkwrite
callbacks to do the same by returning early on VM_FAULT_RETRY.

In particular we want to be able to drop the mmap_sem when waiting for
a reservation object lock on a GPU buffer object. These locks may be
held while waiting for the GPU.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
---
 mm/memory.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index a52663c0612d..dcd80313cf10 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2144,7 +2144,7 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
 	ret = vmf->vma->vm_ops->page_mkwrite(vmf);
 	/* Restore original flags so that caller is not surprised */
 	vmf->flags = old_flags;
-	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
+	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | VM_FAULT_NOPAGE)))
 		return ret;
 	if (unlikely(!(ret & VM_FAULT_LOCKED))) {
 		lock_page(page);
@@ -2419,7 +2419,7 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
 		vmf->flags |= FAULT_FLAG_MKWRITE;
 		ret = vma->vm_ops->pfn_mkwrite(vmf);
-		if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))
+		if (ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | VM_FAULT_NOPAGE))
 			return ret;
 		return finish_mkwrite_fault(vmf);
 	}
@@ -2440,7 +2440,8 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf)
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
 		tmp = do_page_mkwrite(vmf);
 		if (unlikely(!tmp || (tmp &
-				      (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
+				      (VM_FAULT_ERROR | VM_FAULT_RETRY |
+				       VM_FAULT_NOPAGE)))) {
 			put_page(vmf->page);
 			return tmp;
 		}
@@ -3472,7 +3473,8 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
 		unlock_page(vmf->page);
 		tmp = do_page_mkwrite(vmf);
 		if (unlikely(!tmp ||
-				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
+				(tmp & (VM_FAULT_ERROR | VM_FAULT_RETRY |
+					VM_FAULT_NOPAGE)))) {
 			put_page(vmf->page);
 			return tmp;
 		}
-- 
2.19.0.rc1

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

[RFC PATCH 2/3] mm: Add an apply_to_pfn_range interface

[Thomas Hellstrom]

This is basically apply_to_page_range with added functionality:
Allocating missing parts of the page table becomes optional, which
means that the function can be guaranteed not to error if allocation
is disabled. Also passing of the closure struct and callback function
becomes different and more in line with how things are done elsewhere.

Finally we keep apply_to_page_range as a wrapper around apply_to_pfn_range

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
---
 include/linux/mm.h |  10 ++++
 mm/memory.c        | 121 +++++++++++++++++++++++++++++++++------------
 2 files changed, 99 insertions(+), 32 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 80bb6408fe73..b7dd4ddd6efb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2632,6 +2632,16 @@ typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
 extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
 			       unsigned long size, pte_fn_t fn, void *data);
 
+struct pfn_range_apply;
+typedef int (*pter_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
+			 struct pfn_range_apply *closure);
+struct pfn_range_apply {
+	struct mm_struct *mm;
+	pter_fn_t ptefn;
+	unsigned int alloc;
+};
+extern int apply_to_pfn_range(struct pfn_range_apply *closure,
+			      unsigned long address, unsigned long size);
 
 #ifdef CONFIG_PAGE_POISONING
 extern bool page_poisoning_enabled(void);
diff --git a/mm/memory.c b/mm/memory.c
index dcd80313cf10..0feb7191c2d2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1938,18 +1938,17 @@ int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long
 }
 EXPORT_SYMBOL(vm_iomap_memory);
 
-static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
-				     unsigned long addr, unsigned long end,
-				     pte_fn_t fn, void *data)
+static int apply_to_pte_range(struct pfn_range_apply *closure, pmd_t *pmd,
+			      unsigned long addr, unsigned long end)
 {
 	pte_t *pte;
 	int err;
 	pgtable_t token;
 	spinlock_t *uninitialized_var(ptl);
 
-	pte = (mm == &init_mm) ?
+	pte = (closure->mm == &init_mm) ?
 		pte_alloc_kernel(pmd, addr) :
-		pte_alloc_map_lock(mm, pmd, addr, &ptl);
+		pte_alloc_map_lock(closure->mm, pmd, addr, &ptl);
 	if (!pte)
 		return -ENOMEM;
 
@@ -1960,86 +1959,103 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
 	token = pmd_pgtable(*pmd);
 
 	do {
-		err = fn(pte++, token, addr, data);
+		err = closure->ptefn(pte++, token, addr, closure);
 		if (err)
 			break;
 	} while (addr += PAGE_SIZE, addr != end);
 
 	arch_leave_lazy_mmu_mode();
 
-	if (mm != &init_mm)
+	if (closure->mm != &init_mm)
 		pte_unmap_unlock(pte-1, ptl);
 	return err;
 }
 
-static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
-				     unsigned long addr, unsigned long end,
-				     pte_fn_t fn, void *data)
+static int apply_to_pmd_range(struct pfn_range_apply *closure, pud_t *pud,
+			      unsigned long addr, unsigned long end)
 {
 	pmd_t *pmd;
 	unsigned long next;
-	int err;
+	int err = 0;
 
 	BUG_ON(pud_huge(*pud));
 
-	pmd = pmd_alloc(mm, pud, addr);
+	pmd = pmd_alloc(closure->mm, pud, addr);
 	if (!pmd)
 		return -ENOMEM;
+
 	do {
 		next = pmd_addr_end(addr, end);
-		err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
+		if (!closure->alloc && pmd_none_or_clear_bad(pmd))
+			continue;
+		err = apply_to_pte_range(closure, pmd, addr, next);
 		if (err)
 			break;
 	} while (pmd++, addr = next, addr != end);
 	return err;
 }
 
-static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d,
-				     unsigned long addr, unsigned long end,
-				     pte_fn_t fn, void *data)
+static int apply_to_pud_range(struct pfn_range_apply *closure, p4d_t *p4d,
+			      unsigned long addr, unsigned long end)
 {
 	pud_t *pud;
 	unsigned long next;
-	int err;
+	int err = 0;
 
-	pud = pud_alloc(mm, p4d, addr);
+	pud = pud_alloc(closure->mm, p4d, addr);
 	if (!pud)
 		return -ENOMEM;
+
 	do {
 		next = pud_addr_end(addr, end);
-		err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
+		if (!closure->alloc && pud_none_or_clear_bad(pud))
+			continue;
+		err = apply_to_pmd_range(closure, pud, addr, next);
 		if (err)
 			break;
 	} while (pud++, addr = next, addr != end);
 	return err;
 }
 
-static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
-				     unsigned long addr, unsigned long end,
-				     pte_fn_t fn, void *data)
+static int apply_to_p4d_range(struct pfn_range_apply *closure, pgd_t *pgd,
+			      unsigned long addr, unsigned long end)
 {
 	p4d_t *p4d;
 	unsigned long next;
-	int err;
+	int err = 0;
 
-	p4d = p4d_alloc(mm, pgd, addr);
+	p4d = p4d_alloc(closure->mm, pgd, addr);
 	if (!p4d)
 		return -ENOMEM;
+
 	do {
 		next = p4d_addr_end(addr, end);
-		err = apply_to_pud_range(mm, p4d, addr, next, fn, data);
+		if (!closure->alloc && p4d_none_or_clear_bad(p4d))
+			continue;
+		err = apply_to_pud_range(closure, p4d, addr, next);
 		if (err)
 			break;
 	} while (p4d++, addr = next, addr != end);
 	return err;
 }
 
-/*
- * Scan a region of virtual memory, filling in page tables as necessary
- * and calling a provided function on each leaf page table.
+/**
+ * apply_to_pfn_range - Scan a region of virtual memory, calling a provided
+ * function on each leaf page table entry
+ * @closure: Details about how to scan and what function to apply
+ * @addr: Start virtual address
+ * @size: Size of the region
+ *
+ * If @closure->alloc is set to 1, the function will fill in the page table
+ * as necessary. Otherwise it will skip non-present parts.
+ *
+ * Returns: Zero on success. If the provided function returns a non-zero status,
+ * the page table walk will terminate and that status will be returned.
+ * If @closure->alloc is set to 1, then this function may also return memory
+ * allocation errors arising from allocating page table memory.
  */
-int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
-			unsigned long size, pte_fn_t fn, void *data)
+int apply_to_pfn_range(struct pfn_range_apply *closure,
+		       unsigned long addr, unsigned long size)
 {
 	pgd_t *pgd;
 	unsigned long next;
@@ -2049,16 +2065,57 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
 	if (WARN_ON(addr >= end))
 		return -EINVAL;
 
-	pgd = pgd_offset(mm, addr);
+	pgd = pgd_offset(closure->mm, addr);
 	do {
 		next = pgd_addr_end(addr, end);
-		err = apply_to_p4d_range(mm, pgd, addr, next, fn, data);
+		if (!closure->alloc && pgd_none_or_clear_bad(pgd))
+			continue;
+		err = apply_to_p4d_range(closure, pgd, addr, next);
 		if (err)
 			break;
 	} while (pgd++, addr = next, addr != end);
 
 	return err;
 }
+EXPORT_SYMBOL_GPL(apply_to_pfn_range);
+
+struct page_range_apply {
+	struct pfn_range_apply pter;
+	pte_fn_t fn;
+	void *data;
+};
+
+/*
+ * Callback wrapper to enable use of apply_to_pfn_range for
+ * the apply_to_page_range interface
+ */
+static int apply_to_page_range_wrapper(pte_t *pte, pgtable_t token,
+				       unsigned long addr,
+				       struct pfn_range_apply *pter)
+{
+	struct page_range_apply *pra =
+		container_of(pter, typeof(*pra), pter);
+
+	return pra->fn(pte, token, addr, pra->data);
+}
+
+/*
+ * Scan a region of virtual memory, filling in page tables as necessary
+ * and calling a provided function on each leaf page table.
+ */
+int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
+			unsigned long size, pte_fn_t fn, void *data)
+{
+	struct page_range_apply pra = {
+		.pter = {.mm = mm,
+			 .alloc = 1,
+			 .ptefn = apply_to_page_range_wrapper },
+		.fn = fn,
+		.data = data
+	};
+
+	return apply_to_pfn_range(&pra.pter, addr, size);
+}
 EXPORT_SYMBOL_GPL(apply_to_page_range);
 
 /*
-- 
2.19.0.rc1

[RFC PATCH 3/3] mm: Add write-protect and clean utilities for address space ranges

[Thomas Hellstrom]

Add two utilities to a) write-protect and b) clean all ptes pointing into
a range of an address space
The utilities are intended to aid in tracking dirty pages (either
driver-allocated system memory or pci device memory).
The write-protect utility should be used in conjunction with
page_mkwrite() and pfn_mkwrite() to trigger write page-faults on page
accesses. Typically one would want to use this on sparse accesses into
large memory regions. The clean utility should be used to utilize
hardware dirtying functionality and avoid the overhead of page-faults,
typically on large accesses into small memory regions.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
---
 include/linux/mm.h  |   9 +-
 mm/Makefile         |   2 +-
 mm/apply_as_range.c | 257 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 266 insertions(+), 2 deletions(-)
 create mode 100644 mm/apply_as_range.c

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b7dd4ddd6efb..62f24dd0bfa0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2642,7 +2642,14 @@ struct pfn_range_apply {
 };
 extern int apply_to_pfn_range(struct pfn_range_apply *closure,
 			      unsigned long address, unsigned long size);
-
+unsigned long apply_as_wrprotect(struct address_space *mapping,
+				 pgoff_t first_index, pgoff_t nr);
+unsigned long apply_as_clean(struct address_space *mapping,
+			     pgoff_t first_index, pgoff_t nr,
+			     pgoff_t bitmap_pgoff,
+			     unsigned long *bitmap,
+			     pgoff_t *start,
+			     pgoff_t *end);
 #ifdef CONFIG_PAGE_POISONING
 extern bool page_poisoning_enabled(void);
 extern void kernel_poison_pages(struct page *page, int numpages, int enable);
diff --git a/mm/Makefile b/mm/Makefile
index d210cc9d6f80..a94b78f12692 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -39,7 +39,7 @@ obj-y			:= filemap.o mempool.o oom_kill.o fadvise.o \
 			   mm_init.o mmu_context.o percpu.o slab_common.o \
 			   compaction.o vmacache.o \
 			   interval_tree.o list_lru.o workingset.o \
-			   debug.o $(mmu-y)
+			   debug.o apply_as_range.o $(mmu-y)
 
 obj-y += init-mm.o
 obj-y += memblock.o
diff --git a/mm/apply_as_range.c b/mm/apply_as_range.c
new file mode 100644
index 000000000000..9f03e272ebd0
--- /dev/null
+++ b/mm/apply_as_range.c
@@ -0,0 +1,257 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/mm.h>
+#include <linux/mm_types.h>
+#include <linux/hugetlb.h>
+#include <linux/bitops.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+/**
+ * struct apply_as - Closure structure for apply_as_range
+ * @base: struct pfn_range_apply we derive from
+ * @start: Address of first modified pte
+ * @end: Address of last modified pte + 1
+ * @total: Total number of modified ptes
+ * @vma: Pointer to the struct vm_area_struct we're currently operating on
+ * @flush_cache: Whether to call a cache flush before modifying a pte
+ * @flush_tlb: Whether to flush the tlb after modifying a pte
+ */
+struct apply_as {
+	struct pfn_range_apply base;
+	unsigned long start, end;
+	unsigned long total;
+	const struct vm_area_struct *vma;
+	u32 flush_cache : 1;
+	u32 flush_tlb : 1;
+};
+
+/**
+ * apply_pt_wrprotect - Leaf pte callback to write-protect a pte
+ * @pte: Pointer to the pte
+ * @token: Page table token, see apply_to_pfn_range()
+ * @addr: The virtual page address
+ * @closure: Pointer to a struct pfn_range_apply embedded in a
+ * struct apply_as
+ *
+ * The function write-protects a pte and records the range in
+ * virtual address space of touched ptes for efficient TLB flushes.
+ *
+ * Return: Always zero.
+ */
+static int apply_pt_wrprotect(pte_t *pte, pgtable_t token,
+			      unsigned long addr,
+			      struct pfn_range_apply *closure)
+{
+	struct apply_as *aas = container_of(closure, typeof(*aas), base);
+
+	if (pte_write(*pte)) {
+		set_pte_at(closure->mm, addr, pte, pte_wrprotect(*pte));
+		aas->total++;
+		if (addr < aas->start)
+			aas->start = addr;
+		if (addr + PAGE_SIZE > aas->end)
+			aas->end = addr + PAGE_SIZE;
+	}
+
+	return 0;
+}
+
+/**
+ * struct apply_as_clean - Closure structure for apply_as_clean
+ * @base: struct apply_as we derive from
+ * @bitmap_pgoff: Address_space Page offset of the first bit in @bitmap
+ * @bitmap: Bitmap with one bit for each page offset in the address_space range
+ * covered.
+ * @start: Address_space page offset of first modified pte
+ * @end: Address_space page offset of last modified pte
+ */
+struct apply_as_clean {
+	struct apply_as base;
+	pgoff_t bitmap_pgoff;
+	unsigned long *bitmap;
+	pgoff_t start, end;
+};
+
+/**
+ * apply_pt_clean - Leaf pte callback to clean a pte
+ * @pte: Pointer to the pte
+ * @token: Page table token, see apply_to_pfn_range()
+ * @addr: The virtual page address
+ * @closure: Pointer to a struct pfn_range_apply embedded in a
+ * struct apply_as_clean
+ *
+ * The function cleans a pte and records the range in
+ * virtual address space of touched ptes for efficient TLB flushes.
+ * It also records dirty ptes in a bitmap representing page offsets
+ * in the address_space, as well as the first and last of the bits
+ * touched.
+ *
+ * Return: Always zero.
+ */
+static int apply_pt_clean(pte_t *pte, pgtable_t token,
+			  unsigned long addr,
+			  struct pfn_range_apply *closure)
+{
+	struct apply_as *aas = container_of(closure, typeof(*aas), base);
+	struct apply_as_clean *clean = container_of(aas, typeof(*clean), base);
+
+	if (pte_dirty(*pte)) {
+		pgoff_t pgoff = ((addr - aas->vma->vm_start) >> PAGE_SHIFT) +
+			aas->vma->vm_pgoff - clean->bitmap_pgoff;
+
+		set_pte_at(closure->mm, addr, pte, pte_mkclean(*pte));
+		aas->total++;
+		if (addr < aas->start)
+			aas->start = addr;
+		if (addr + PAGE_SIZE > aas->end)
+			aas->end = addr + PAGE_SIZE;
+
+		__set_bit(pgoff, clean->bitmap);
+		clean->start = min(clean->start, pgoff);
+		clean->end = max(clean->end, pgoff + 1);
+	}
+
+	return 0;
+}
+
+/**
+ * apply_as_range - Apply a pte callback to all PTEs pointing into a range
+ * of an address_space.
+ * @mapping: Pointer to the struct address_space
+ * @aas: Closure structure
+ * @first_index: First page offset in the address_space
+ * @nr: Number of incremental page offsets to cover
+ *
+ * Return: Number of ptes touched. Note that this number might be larger
+ * than @nr if there are overlapping vmas
+ */
+static unsigned long apply_as_range(struct address_space *mapping,
+				    struct apply_as *aas,
+				    pgoff_t first_index, pgoff_t nr)
+{
+	struct vm_area_struct *vma;
+	pgoff_t vba, vea, cba, cea;
+	unsigned long start_addr, end_addr;
+
+	/* FIXME: Is a read lock sufficient here? */
+	down_write(&mapping->i_mmap_rwsem);
+	vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
+		first_index + nr - 1) {
+		aas->base.mm = vma->vm_mm;
+
+		/* Clip to the vma */
+		vba = vma->vm_pgoff;
+		vea = vba + vma_pages(vma);
+		cba = first_index;
+		cba = max(cba, vba);
+		cea = first_index + nr;
+		cea = min(cea, vea);
+
+		/* Translate to virtual address */
+		start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
+		end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
+
+		/*
+		 * TODO: Should caches be flushed individually on demand
+		 * in the leaf-pte callbacks instead? That is, how
+		 * costly are inter-core interrupts in an SMP system?
+		 */
+		if (aas->flush_cache)
+			flush_cache_range(vma, start_addr, end_addr);
+		aas->start = end_addr;
+		aas->end = start_addr;
+		aas->vma = vma;
+
+		/* Should not error since aas->base.alloc == 0 */
+		WARN_ON(apply_to_pfn_range(&aas->base, start_addr,
+					   end_addr - start_addr));
+		if (aas->flush_tlb && aas->end > aas->start)
+			flush_tlb_range(vma, aas->start, aas->end);
+	}
+	up_write(&mapping->i_mmap_rwsem);
+
+	return aas->total;
+}
+
+/**
+ * apply_as_wrprotect - Write-protect all ptes in an address_space range
+ * @mapping: The address_space we want to write protect
+ * @first_index: The first page offset in the range
+ * @nr: Number of incremental page offsets to cover
+ *
+ * Return: The number of ptes actually write-protected. Note that
+ * already write-protected ptes are not counted.
+ */
+unsigned long apply_as_wrprotect(struct address_space *mapping,
+				 pgoff_t first_index, pgoff_t nr)
+{
+	struct apply_as aas = {
+		.base = {
+			.alloc = 0,
+			.ptefn = apply_pt_wrprotect,
+		},
+		.total = 0,
+		.flush_cache = 1,
+		.flush_tlb = 1
+	};
+
+	return apply_as_range(mapping, &aas, first_index, nr);
+}
+EXPORT_SYMBOL(apply_as_wrprotect);
+
+/**
+ * apply_as_clean - Clean all ptes in an address_space range
+ * @mapping: The address_space we want to clean
+ * @first_index: The first page offset in the range
+ * @nr: Number of incremental page offsets to cover
+ * @bitmap_pgoff: The page offset of the first bit in @bitmap
+ * @bitmap: Pointer to a bitmap of at least @nr bits. The bitmap needs to
+ * cover the whole range @first_index..@first_index + @nr.
+ * @start: Pointer to page offset of the first set bit in @bitmap, or if
+ * none set the value pointed to should be @bitmap_pgoff + @nr. The value
+ * is modified as new bits are set by the function.
+ * @end: Page offset of the last set bit in @bitmap + 1 or @bitmap_pgoff if
+ * none set. The value is modified as new bets are set by the function.
+ *
+ * Note: When this function returns there is no guarantee that a CPU has
+ * not already dirtied new ptes. However it will not clean any ptes not
+ * reported in the bitmap.
+ *
+ * If a caller needs to make sure all dirty ptes are picked up and none
+ * additional are added, it first needs to write-protect the address-space
+ * range and make sure new writers are blocked in page_mkwrite() or
+ * pfn_mkwrite(). And then after a TLB flush following the write-protection
+ * pick upp all dirty bits.
+ *
+ * Return: The number of dirty ptes actually cleaned.
+ */
+unsigned long apply_as_clean(struct address_space *mapping,
+			     pgoff_t first_index, pgoff_t nr,
+			     pgoff_t bitmap_pgoff,
+			     unsigned long *bitmap,
+			     pgoff_t *start,
+			     pgoff_t *end)
+{
+	struct apply_as_clean clean = {
+		.base = {
+			.base = {
+				.alloc = 0,
+				.ptefn = apply_pt_clean,
+			},
+			.total = 0,
+			.flush_cache = 0,
+			.flush_tlb = 1,
+		},
+		.bitmap_pgoff = bitmap_pgoff,
+		.bitmap = bitmap,
+		.start = *start,
+		.end = *end,
+	};
+	unsigned long ret = apply_as_range(mapping, &clean.base, first_index,
+					   nr);
+
+	*start = clean.start;
+	*end = clean.end;
+	return ret;
+}
+EXPORT_SYMBOL(apply_as_clean);
-- 
2.19.0.rc1

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [RFC PATCH 1/3] mm: Allow the [page|pfn]_mkwrite callbacks to drop the mmap_sem

[Linus Torvalds]

On Wed, Mar 20, 2019 at 8:23 AM Thomas Hellstrom <thellstrom@vmware.com> wrote:
>
> Driver fault callbacks are allowed to drop the mmap_sem when expecting
> long hardware waits [...]

No comment on the patch itself, but please fix your email setup.

All the patches were marked as spam, because you sent them from your
vmware.com address, but without going through the proper vmware smtp
gateway.

So they lack the proper vmware DKIM hashes and proper mail handling
should (and does) consider them spam.

               Linus