Re: [PATCH v3 01/13] X86/nVMX: handle_vmon: Read 4 bytes from guest memory

[Jim Mattson]

On Sat, Oct 20, 2018 at 3:22 PM, KarimAllah Ahmed  wrote:
> Read the data directly from guest memory instead of the map->read->unmap
> sequence. This also avoids using kvm_vcpu_gpa_to_page() and kmap() which
> assumes that there is a "struct page" for guest memory.
>
> Suggested-by: Jim Mattson 
> Signed-off-by: KarimAllah Ahmed 
Reviewed-by: Jim Mattson 

[PATCH v3 01/13] X86/nVMX: handle_vmon: Read 4 bytes from guest memory

[KarimAllah Ahmed]

Read the data directly from guest memory instead of the map->read->unmap
sequence. This also avoids using kvm_vcpu_gpa_to_page() and kmap() which
assumes that there is a "struct page" for guest memory.

Suggested-by: Jim Mattson 
Signed-off-by: KarimAllah Ahmed 
---
v1 -> v2:
- Massage commit message a bit.
---
 arch/x86/kvm/vmx.c | 14 +++---
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4f5d4bd..358759a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8321,7 +8321,7 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
 {
int ret;
gpa_t vmptr;
-   struct page *page;
+   uint32_t revision;
struct vcpu_vmx *vmx = to_vmx(vcpu);
const u64 VMXON_NEEDED_FEATURES = FEATURE_CONTROL_LOCKED
| FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
@@ -8373,19 +8373,11 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
return kvm_skip_emulated_instruction(vcpu);
}
 
-   page = kvm_vcpu_gpa_to_page(vcpu, vmptr);
-   if (is_error_page(page)) {
+   if (kvm_read_guest(vcpu->kvm, vmptr, &revision, sizeof(revision)) ||
+   revision != VMCS12_REVISION) {
nested_vmx_failInvalid(vcpu);
return kvm_skip_emulated_instruction(vcpu);
}
-   if (*(u32 *)kmap(page) != VMCS12_REVISION) {
-   kunmap(page);
-   kvm_release_page_clean(page);
-   nested_vmx_failInvalid(vcpu);
-   return kvm_skip_emulated_instruction(vcpu);
-   }
-   kunmap(page);
-   kvm_release_page_clean(page);
 
vmx->nested.vmxon_ptr = vmptr;
ret = enter_vmx_operation(vcpu);
-- 
2.7.4