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kvm: Map PFN-type memory regions as writable (if possible)

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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@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
KarimAllah Ahmed 2018-01-17 19:18:56 +01:00 committed by Radim Krčmář
parent e53175395d
commit a340b3e229
1 changed files with 5 additions and 2 deletions
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7
virt/kvm/kvm_main.c
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@ -1428,7 +1428,8 @@ 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;
@ -1454,6 +1455,8 @@ 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
@ -1519,7 +1522,7 @@ 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)