KVM: nVMX: Cache shadow vmcs12 on VMEntry and flush to memory on VMExit

This is done is done as a preparation to VMCS shadowing emulation.

Signed-off-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f8ad42b..2a005f5 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -645,6 +645,12 @@ struct nested_vmx {
         */
        struct vmcs12 *cached_vmcs12;
        /*
+        * Cache of the guest's shadow VMCS, existing outside of guest
+        * memory. Loaded from guest memory during VM entry. Flushed
+        * to guest memory during VM exit.
+        */
+       struct vmcs12 *cached_shadow_vmcs12;
+       /*
         * Indicates if the shadow vmcs must be updated with the
         * data hold by vmcs12
         */
@@ -1076,6 +1082,11 @@ static inline struct vmcs12 *get_vmcs12(struct kvm_vcpu *vcpu)
        return to_vmx(vcpu)->nested.cached_vmcs12;
 }
 
+static inline struct vmcs12 *get_shadow_vmcs12(struct kvm_vcpu *vcpu)
+{
+       return to_vmx(vcpu)->nested.cached_shadow_vmcs12;
+}
+
 static bool nested_ept_ad_enabled(struct kvm_vcpu *vcpu);
 static unsigned long nested_ept_get_cr3(struct kvm_vcpu *vcpu);
 static u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa);
@@ -7900,6 +7911,10 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)
        if (!vmx->nested.cached_vmcs12)
                goto out_cached_vmcs12;
 
+       vmx->nested.cached_shadow_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL);
+       if (!vmx->nested.cached_shadow_vmcs12)
+               goto out_cached_shadow_vmcs12;
+
        if (enable_shadow_vmcs) {
                shadow_vmcs = alloc_vmcs();
                if (!shadow_vmcs)
@@ -7919,6 +7934,9 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)
        return 0;
 
 out_shadow_vmcs:
+       kfree(vmx->nested.cached_shadow_vmcs12);
+
+out_cached_shadow_vmcs12:
        kfree(vmx->nested.cached_vmcs12);
 
 out_cached_vmcs12:
@@ -8085,6 +8103,7 @@ static void free_nested(struct vcpu_vmx *vmx)
                vmx->vmcs01.shadow_vmcs = NULL;
        }
        kfree(vmx->nested.cached_vmcs12);
+       kfree(vmx->nested.cached_shadow_vmcs12);
        /* Unpin physical memory we referred to in the vmcs02 */
        if (vmx->nested.apic_access_page) {
                kvm_release_page_dirty(vmx->nested.apic_access_page);
@@ -10926,6 +10945,38 @@ static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
        return true;
 }
 
+static void nested_cache_shadow_vmcs12(struct kvm_vcpu *vcpu,
+                                      struct vmcs12 *vmcs12)
+{
+       struct vmcs12 *shadow;
+       struct page *page;
+
+       if (!nested_cpu_has_shadow_vmcs(vmcs12) ||
+           vmcs12->vmcs_link_pointer == -1ull)
+               return;
+
+       shadow = get_shadow_vmcs12(vcpu);
+       page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->vmcs_link_pointer);
+
+       memcpy(shadow, kmap(page), VMCS12_SIZE);
+
+       kunmap(page);
+       kvm_release_page_clean(page);
+}
+
+static void nested_flush_cached_shadow_vmcs12(struct kvm_vcpu *vcpu,
+                                             struct vmcs12 *vmcs12)
+{
+       struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+       if (!nested_cpu_has_shadow_vmcs(vmcs12) ||
+           vmcs12->vmcs_link_pointer == -1ull)
+               return;
+
+       kvm_write_guest(vmx->vcpu.kvm, vmcs12->vmcs_link_pointer,
+                       get_shadow_vmcs12(vcpu), VMCS12_SIZE);
+}
+
 static int nested_vmx_check_apic_access_controls(struct kvm_vcpu *vcpu,
                                          struct vmcs12 *vmcs12)
 {
@@ -11996,6 +12047,18 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
        }
 
        /*
+        * Must happen outside of enter_vmx_non_root_mode() as it will
+        * also be used as part of restoring nVMX state for
+        * snapshot restore (migration).
+        *
+        * In this flow, it is assumed that vmcs12 cache was
+        * trasferred as part of captured nVMX state and should
+        * therefore not be read from guest memory (which may not
+        * exist on destination host yet).
+        */
+       nested_cache_shadow_vmcs12(vcpu, vmcs12);
+
+       /*
         * If we're entering a halted L2 vcpu and the L2 vcpu won't be woken
         * by event injection, halt vcpu.
         */
@@ -12504,6 +12567,17 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
                        prepare_vmcs12(vcpu, vmcs12, exit_reason, exit_intr_info,
                                       exit_qualification);
 
+               /*
+                * Must happen outside of sync_vmcs12() as it will
+                * also be used to capture vmcs12 cache as part of
+                * capturing nVMX state for snapshot (migration).
+                *
+                * Otherwise, this flush will dirty guest memory at a
+                * point it is already assumed by user-space to be
+                * immutable.
+                */
+               nested_flush_cached_shadow_vmcs12(vcpu, vmcs12);
+
                if (nested_vmx_store_msr(vcpu, vmcs12->vm_exit_msr_store_addr,
                                         vmcs12->vm_exit_msr_store_count))
                        nested_vmx_abort(vcpu, VMX_ABORT_SAVE_GUEST_MSR_FAIL);