On 17/01/2018 19:18, KarimAllah Ahmed wrote:
> 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
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> 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)
>
