| From foo@baz Sun May 27 17:33:38 CEST 2018 |
| From: KarimAllah Ahmed <karahmed@amazon.de> |
| Date: Wed, 17 Jan 2018 19:18:56 +0100 |
| Subject: kvm: Map PFN-type memory regions as writable (if possible) |
| |
| From: KarimAllah Ahmed <karahmed@amazon.de> |
| |
| [ Upstream commit a340b3e229b24a56f1c7f5826b15a3af0f4b13e5 ] |
| |
| 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> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| virt/kvm/kvm_main.c | 7 +++++-- |
| 1 file changed, 5 insertions(+), 2 deletions(-) |
| |
| --- a/virt/kvm/kvm_main.c |
| +++ b/virt/kvm/kvm_main.c |
| @@ -1466,7 +1466,8 @@ static bool vma_is_valid(struct vm_area_ |
| |
| 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; |
| @@ -1492,6 +1493,8 @@ static int hva_to_pfn_remapped(struct vm |
| |
| } |
| |
| + if (writable) |
| + *writable = true; |
| |
| /* |
| * Get a reference here because callers of *hva_to_pfn* and |
| @@ -1557,7 +1560,7 @@ retry: |
| 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) |
