KVM: nVMX: Use kvm_read_guest_offset_cached() for nested VMCS check

Kill another mostly gratuitous kvm_vcpu_map() which could just use the
userspace HVA for it.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20211115165030.7422-6-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index fff6b32..4fb904f 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2925,9 +2925,9 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
 static int nested_vmx_check_vmcs_link_ptr(struct kvm_vcpu *vcpu,
                                          struct vmcs12 *vmcs12)
 {
-       int r = 0;
-       struct vmcs12 *shadow;
-       struct kvm_host_map map;
+       struct vcpu_vmx *vmx = to_vmx(vcpu);
+       struct gfn_to_hva_cache *ghc = &vmx->nested.shadow_vmcs12_cache;
+       struct vmcs_hdr hdr;
 
        if (vmcs12->vmcs_link_pointer == INVALID_GPA)
                return 0;
@@ -2935,17 +2935,21 @@ static int nested_vmx_check_vmcs_link_ptr(struct kvm_vcpu *vcpu,
        if (CC(!page_address_valid(vcpu, vmcs12->vmcs_link_pointer)))
                return -EINVAL;
 
-       if (CC(kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->vmcs_link_pointer), &map)))
-               return -EINVAL;
+       if (ghc->gpa != vmcs12->vmcs_link_pointer &&
+           CC(kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc,
+                                        vmcs12->vmcs_link_pointer, VMCS12_SIZE)))
+                return -EINVAL;
 
-       shadow = map.hva;
+       if (CC(kvm_read_guest_offset_cached(vcpu->kvm, ghc, &hdr,
+                                           offsetof(struct vmcs12, hdr),
+                                           sizeof(hdr))))
+               return -EINVAL;
 
-       if (CC(shadow->hdr.revision_id != VMCS12_REVISION) ||
-           CC(shadow->hdr.shadow_vmcs != nested_cpu_has_shadow_vmcs(vmcs12)))
-               r = -EINVAL;
+       if (CC(hdr.revision_id != VMCS12_REVISION) ||
+           CC(hdr.shadow_vmcs != nested_cpu_has_shadow_vmcs(vmcs12)))
+               return -EINVAL;
 
-       kvm_vcpu_unmap(vcpu, &map, false);
-       return r;
+       return 0;
 }
 
 /*