[15/22] KVM: nVMX: Allocate bitmaps for virtualizing VMCS shadowing

Commit Message

Liran Alon June 22, 2018, 11:35 p.m. UTC

We can't really use the L1 guest's vmread and vmwrite bitmaps
directly, because virtual and physical hardware may not support the
same VMCS fields. This change allocates pages for the "cleaned"
versions of the L1 guest's vmread and vmwrite bitmaps. These bitmaps
do not yet reflect the desires of the L1 hypervisor. All bits are set,
so we can enable VMCS shadowing in hardware, and every VMREAD or
VMWRITE will result in an VM-exit to L0, which emulates VMCS shadowing
as it did before this change.

Signed-off-by: Liran Alon <[e-mail]>
Signed-off-by: Jim Mattson <[e-mail]>
---
 arch/x86/kvm/vmx.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 69 insertions(+), 9 deletions(-)

Patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 99576c2fa65a..3327bd7fe81f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -675,6 +675,9 @@  struct nested_vmx {
 	bool pi_pending;
 	u16 posted_intr_nv;
 
+	unsigned long *vmread_bitmap;
+	unsigned long *vmwrite_bitmap;
+
 	struct hrtimer preemption_timer;
 	bool preemption_timer_expired;
 
@@ -8088,6 +8091,14 @@  static void free_nested(struct vcpu_vmx *vmx)
 		vmcs_clear(vmx->vmcs01.shadow_vmcs);
 		free_vmcs(vmx->vmcs01.shadow_vmcs);
 		vmx->vmcs01.shadow_vmcs = NULL;
+		if (vmx->nested.vmread_bitmap) {
+			free_page((unsigned long)vmx->nested.vmread_bitmap);
+			vmx->nested.vmread_bitmap = NULL;
+		}
+		if (vmx->nested.vmwrite_bitmap) {
+			free_page((unsigned long)vmx->nested.vmwrite_bitmap);
+			vmx->nested.vmwrite_bitmap = NULL;
+		}
 	}
 	kfree(vmx->nested.cached_vmcs12);
 	kfree(vmx->nested.cached_shadow_vmcs12);
@@ -11313,6 +11324,40 @@  static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
 	return 0;
 }
 
+/*
+ * Allocate three pages for virtualizing VMCS shadowing: the shadow
+ * itself and the vmread and vmwrite bitmaps. These pages are
+ * allocated when first needed and freed when leaving virtual VMX
+ * operation. If previously allocated, the existing pages are
+ * reused. When first allocated, the VMREAD and VMWRITE bitmaps are
+ * initialized to all 1's.
+ */
+static int alloc_vmcs_shadowing_pages(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+	if (!alloc_shadow_vmcs(vcpu))
+		return -ENOMEM;
+
+	if (!vmx->nested.vmread_bitmap) {
+		vmx->nested.vmread_bitmap =
+			(unsigned long *)__get_free_page(GFP_KERNEL);
+		if (!vmx->nested.vmread_bitmap)
+			return -ENOMEM;
+		memset(vmx->nested.vmread_bitmap, 0xff, PAGE_SIZE);
+	}
+
+	if (!vmx->nested.vmwrite_bitmap) {
+		vmx->nested.vmwrite_bitmap =
+			(unsigned long *)__get_free_page(GFP_KERNEL);
+		if (!vmx->nested.vmwrite_bitmap)
+			return -ENOMEM;
+		memset(vmx->nested.vmwrite_bitmap, 0xff, PAGE_SIZE);
+	}
+
+	return 0;
+}
+
 static void prepare_vmcs02_full(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -11358,12 +11403,6 @@  static void prepare_vmcs02_full(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 	if (nested_cpu_has_xsaves(vmcs12))
 		vmcs_write64(XSS_EXIT_BITMAP, vmcs12->xss_exit_bitmap);
 
-	if (nested_cpu_has2(vmcs12, SECONDARY_EXEC_SHADOW_VMCS) &&
-	    enable_shadow_vmcs && alloc_shadow_vmcs(vcpu)) {
-		/* TODO: IMPLEMENT */
-	}
-	vmcs_write64(VMCS_LINK_POINTER, -1ull);
-
 	if (cpu_has_vmx_posted_intr())
 		vmcs_write16(POSTED_INTR_NV, POSTED_INTR_NESTED_VECTOR);
 
@@ -11534,6 +11573,7 @@  static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 				  SECONDARY_EXEC_XSAVES |
 				  SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
 				  SECONDARY_EXEC_APIC_REGISTER_VIRT |
+				  SECONDARY_EXEC_SHADOW_VMCS |
 				  SECONDARY_EXEC_ENABLE_VMFUNC);
 		if (nested_cpu_has(vmcs12,
 				   CPU_BASED_ACTIVATE_SECONDARY_CONTROLS)) {
@@ -11542,9 +11582,6 @@  static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 			exec_control |= vmcs12_exec_ctrl;
 		}
 
-		/* VMCS shadowing for L2 is emulated for now */
-		exec_control &= ~SECONDARY_EXEC_SHADOW_VMCS;
-
 		if (exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY)
 			vmcs_write16(GUEST_INTR_STATUS,
 				vmcs12->guest_intr_status);
@@ -11557,6 +11594,29 @@  static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		if (exec_control & SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)
 			vmcs_write64(APIC_ACCESS_ADDR, -1ull);
 
+		/*
+		 * If L0 enables VMCS shadowing and vmcs12 enables
+		 * VMCS shadowing, virtualize VMCS shadowing by
+		 * allocating a shadow VMCS and vmread/vmwrite bitmaps
+		 * for vmcs02. vmread/vmwrite bitmaps are init at this
+		 * point to intercept all vmread/vmwrite.
+		 *
+		 * Otherwise, emulate VMCS shadowing by disabling VMCS
+		 * shadowing at vmcs02 and emulate vmread/vmwrite to
+		 * read/write from/to shadow vmcs12.
+		 */
+		if ((exec_control & SECONDARY_EXEC_SHADOW_VMCS) &&
+		    enable_shadow_vmcs && !alloc_vmcs_shadowing_pages(vcpu)) {
+			vmcs_write64(VMCS_LINK_POINTER,
+				     vmcs12->vmcs_link_pointer == -1ull ?
+				     -1ull : __pa(vmx->loaded_vmcs->shadow_vmcs));
+			vmcs_write64(VMREAD_BITMAP, __pa(vmx->nested.vmread_bitmap));
+			vmcs_write64(VMWRITE_BITMAP, __pa(vmx->nested.vmwrite_bitmap));
+		} else {
+			exec_control &= ~SECONDARY_EXEC_SHADOW_VMCS;
+			vmcs_write64(VMCS_LINK_POINTER, -1ull);
+		}
+
 		vmcs_write32(SECONDARY_VM_EXEC_CONTROL, exec_control);
 	}