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KVM: attempt async pf only if address is contained in vma

PATCH Marcelo Tosatti 2 participants 5 messages Oct 18, 2010 – Oct 19, 2010 KVM

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Marcelo Tosatti

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#0 lore raw

Only attempt async pagefault if address is contained within vma.

Signed-off-by Marcelo Tosatti <[email protected]>
virt/kvm/kvm_main.c +3 -2
index 5d57ec9..a9cfbd2 100644
@@ -996,8 +996,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 
 		if (vma == NULL || addr < vma->vm_start ||
 		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+			if (async && vma && !(vma->vm_flags & VM_PFNMAP) &&
+			    (vma->vm_flags & VM_WRITE) &&
+			    addr >= vma->vm_start)
 				*async = true;
 			up_read(&current->mm->mmap_sem);
 return_fault_page:
#1 lore raw
Quoted 10 lines · Marcelo Tosatti

Only attempt async pagefault if address is contained within vma.

Signed-off-by Marcelo Tosatti <[email protected]>
virt/kvm/kvm_main.c +0 -0
index 5d57ec9..a9cfbd2 100644

virt/kvm/kvm_main.c static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, · line 999

Quoted 6 lines
virt/kvm/kvm_main.c +1 -2
@@ -996,8 +996,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 
 		if (vma == NULL || addr < vma->vm_start ||
 		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+			if (async && vma && !(vma->vm_flags & VM_PFNMAP) &&

actually we should check for addr < vma->vm_start here too. find_vma() is very strange function.

What about patch below (only compile tested for now)?

virt/kvm/kvm_main.c +17 -13
index 796b06e..29e40e5 100644
@@ -954,6 +954,12 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_hva);
 
+static pfn_t get_fault_pfn(void)
+{
+	get_page(fault_page);
+	return fault_pfn;
+}
+
 static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 			bool *async)
 {

@@ -983,7 +989,7 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 		struct vm_area_struct *vma;
 
 		if (atomic)
-			goto return_fault_page;
+			return get_fault_pfn();
 
 		down_read(&current->mm->mmap_sem);
 		if (is_hwpoison_address(addr)) {

@@ -992,22 +998,20 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 			return page_to_pfn(hwpoison_page);
 		}
 
-		vma = find_vma(current->mm, addr);
+		vma = find_vma_intersection(current->mm, addr, addr+1);
 
-		if (vma == NULL || addr < vma->vm_start ||
-		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+		if (vma == NULL)
+			return get_fault_pfn();
+		if ((vma->vm_flags & VM_PFNMAP)) {
+			pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) +
+				vma->vm_pgoff;
+			BUG_ON(!kvm_is_mmio_pfn(pfn));
+		} else {
+			if (async && (vma->vm_flags & VM_WRITE))
 				*async = true;
-			up_read(&current->mm->mmap_sem);
-return_fault_page:
-			get_page(fault_page);
-			return page_to_pfn(fault_page);
+			pfn = get_fault_pfn();
 		}
-
-		pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 		up_read(&current->mm->mmap_sem);
-		BUG_ON(!kvm_is_mmio_pfn(pfn));
 	} else
 		pfn = page_to_pfn(page[0]);

--
Gleb.

#2 lore raw
Quoted 20 lines · Gleb Natapov
Quoted 10 lines · Marcelo Tosatti

Only attempt async pagefault if address is contained within vma.

Signed-off-by Marcelo Tosatti <[email protected]>
virt/kvm/kvm_main.c +0 -0
index 5d57ec9..a9cfbd2 100644

virt/kvm/kvm_main.c static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, · line 999

Quoted 6 lines
virt/kvm/kvm_main.c +1 -2
@@ -996,8 +996,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 
 		if (vma == NULL || addr < vma->vm_start ||
 		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+			if (async && vma && !(vma->vm_flags & VM_PFNMAP) &&

actually we should check for addr < vma->vm_start here too. find_vma() is very strange function.

Quoted 2 lines

What about patch below (only compile tested for now)?

Works for me.

Quoted 60 lines
virt/kvm/kvm_main.c +17 -14
index 796b06e..29e40e5 100644
@@ -954,6 +954,12 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_hva);
 
+static pfn_t get_fault_pfn(void)
+{
+	get_page(fault_page);
+	return fault_pfn;
+}
+
 static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 			bool *async)
 {

@@ -983,7 +989,7 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 		struct vm_area_struct *vma;
 
 		if (atomic)
-			goto return_fault_page;
+			return get_fault_pfn();
 
 		down_read(&current->mm->mmap_sem);
 		if (is_hwpoison_address(addr)) {

@@ -992,22 +998,20 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 			return page_to_pfn(hwpoison_page);
 		}
 
-		vma = find_vma(current->mm, addr);
+		vma = find_vma_intersection(current->mm, addr, addr+1);
 
-		if (vma == NULL || addr < vma->vm_start ||
-		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+		if (vma == NULL)
+			return get_fault_pfn();
+		if ((vma->vm_flags & VM_PFNMAP)) {
+			pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) +
+				vma->vm_pgoff;
+			BUG_ON(!kvm_is_mmio_pfn(pfn));
+		} else {
+			if (async && (vma->vm_flags & VM_WRITE))
 				*async = true;
-			up_read(&current->mm->mmap_sem);
-return_fault_page:
-			get_page(fault_page);
-			return page_to_pfn(fault_page);
+			pfn = get_fault_pfn();
 		}
-
-		pfn = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 		up_read(&current->mm->mmap_sem);
-		BUG_ON(!kvm_is_mmio_pfn(pfn));
 	} else
 		pfn = page_to_pfn(page[0]);
 
--
Quoted 5 lines

Gleb.
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--
Gleb.

author
#3 lore raw
Quoted 21 lines · Gleb Natapov
Quoted 20 lines · Gleb Natapov
Quoted 10 lines · Marcelo Tosatti

Only attempt async pagefault if address is contained within vma.

Signed-off-by Marcelo Tosatti <[email protected]>
virt/kvm/kvm_main.c +0 -0
index 5d57ec9..a9cfbd2 100644

virt/kvm/kvm_main.c static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, · line 999

Quoted 6 lines
virt/kvm/kvm_main.c +1 -2
@@ -996,8 +996,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 
 		if (vma == NULL || addr < vma->vm_start ||
 		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+			if (async && vma && !(vma->vm_flags & VM_PFNMAP) &&

actually we should check for addr < vma->vm_start here too. find_vma() is very strange function.

Quoted 3 lines
Quoted 2 lines

What about patch below (only compile tested for now)?

Works for me.

Thats much nicer.

Quoted 9 lines

virt/kvm/kvm_main.c static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, · line 1004

Quoted 9 lines
virt/kvm/kvm_main.c +3 -5
-		vma = find_vma(current->mm, addr);
+		vma = find_vma_intersection(current->mm, addr, addr+1);
 
-		if (vma == NULL || addr < vma->vm_start ||
-		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+		if (vma == NULL)
+			return get_fault_pfn();

up_read(mmap_sem)

#4 lore raw
Quoted 31 lines · Marcelo Tosatti
Quoted 21 lines · Gleb Natapov
Quoted 20 lines · Gleb Natapov
Quoted 10 lines · Marcelo Tosatti

Only attempt async pagefault if address is contained within vma.

Signed-off-by Marcelo Tosatti <[email protected]>
virt/kvm/kvm_main.c +0 -0
index 5d57ec9..a9cfbd2 100644

virt/kvm/kvm_main.c static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, · line 999

Quoted 6 lines
virt/kvm/kvm_main.c +1 -2
@@ -996,8 +996,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
 
 		if (vma == NULL || addr < vma->vm_start ||
 		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+			if (async && vma && !(vma->vm_flags & VM_PFNMAP) &&

actually we should check for addr < vma->vm_start here too. find_vma() is very strange function.

Quoted 3 lines
Quoted 2 lines

What about patch below (only compile tested for now)?

Works for me.

Thats much nicer.

Quoted 3 lines
Quoted 3 lines
virt/kvm/kvm_main.c +1 -1
-		vma = find_vma(current->mm, addr);
+		vma = find_vma_intersection(current->mm, addr, addr+1);
Quoted 8 lines
Quoted 6 lines

virt/kvm/kvm_main.c static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, · line 1004

Quoted 6 lines
virt/kvm/kvm_main.c +2 -4
-		if (vma == NULL || addr < vma->vm_start ||
-		    !(vma->vm_flags & VM_PFNMAP)) {
-			if (async && !(vma->vm_flags & VM_PFNMAP) &&
-			    (vma->vm_flags & VM_WRITE))
+		if (vma == NULL)
+			return get_fault_pfn();

up_read(mmap_sem)

Oops.

Will resent with fix and all.

--
Gleb.