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SubjectRe: [RFC 05/12] KVM/VMX: Use the new host mapping API for mapping nested vmptr
On Mon, Feb 5, 2018 at 10:49 AM KarimAllah Ahmed <karahmed@amazon.de> wrote:


> @@ -7410,19 +7410,17 @@ 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_vcpu_gpa_to_host_mapping(vcpu, vmptr, &mapping, true)) {
> nested_vmx_failInvalid(vcpu);
> return kvm_skip_emulated_instruction(vcpu);
> }
> - if (*(u32 *)kmap(page) != VMCS12_REVISION) {
> - kunmap(page);
> - kvm_release_page_clean(page);
> + if (*(u32 *)mapping.kaddr != VMCS12_REVISION) {
> + kvm_release_host_mapping(&mapping, false);
> nested_vmx_failInvalid(vcpu);
> return kvm_skip_emulated_instruction(vcpu);
> }
> - kunmap(page);
> - kvm_release_page_clean(page);
> +
> + kvm_release_host_mapping(&mapping, false);

Why go through this explicit mapping/release dance? Why not just:

uint32_t revision;
...
if (kvm_read_guest(vcpu->kvm, vmptr, &revision, sizeof(revision)) ||
revision != VMCS12_REVISION) {
nested_vmx_failInvalid(vcpu);
return kvm_skip_emulated_instruction(vcpu);
}

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