For EPT-violations that are triggered by a read, the pages are also mapped with
write permissions (if their memory region is also writable). That would avoid
getting yet another fault on the same page when a write occurs.
This optimization only happens when you have a "struct page" backing the memory
region. So also enable it for memory regions that do not have a "struct page".
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
---
v2:
- Move setting writable to hva_to_pfn_remapped
- Extend hva_to_pfn_remapped interface to accept writable as a parameter
---
virt/kvm/kvm_main.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 97da45e..88702d5 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1438,7 +1438,8 @@ static bool vma_is_valid(struct vm_area_struct *vma, bool write_fault)
static int hva_to_pfn_remapped(struct vm_area_struct *vma,
unsigned long addr, bool *async,
- bool write_fault, kvm_pfn_t *p_pfn)
+ bool write_fault, bool *writable,
+ kvm_pfn_t *p_pfn)
{
unsigned long pfn;
int r;
@@ -1464,6 +1465,8 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
}
+ if (writable)
+ *writable = true;
/*
* Get a reference here because callers of *hva_to_pfn* and
@@ -1529,7 +1532,7 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
if (vma == NULL)
pfn = KVM_PFN_ERR_FAULT;
else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
- r = hva_to_pfn_remapped(vma, addr, async, write_fault, &pfn);
+ r = hva_to_pfn_remapped(vma, addr, async, write_fault, writable, &pfn);
if (r == -EAGAIN)
goto retry;
if (r < 0)
--
2.7.4
