[PATCH v4 6/8] KVM: x86: nSVM: Save/restore gPAT with KVM_{GET,SET}_NESTED_STATE

[Jim Mattson <jmattson@google.com>]

Add a 'flags' field to the SVM nested state header, and use bit 0 of the
flags to indicate that gPAT is stored in the nested state.

If in guest mode with NPT enabled, store the current vmcb->save.g_pat value
into the header of the nested state, and set the flag.

Note that struct kvm_svm_nested_state_hdr is included in a union padded to
120 bytes, so there is room to add the flags field and the gpat field
without changing any offsets.

Fixes: cc440cdad5b7 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and KVM_SET_NESTED_STATE")
Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/include/uapi/asm/kvm.h |  5 +++++
 arch/x86/kvm/svm/nested.c       | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 846a63215ce1..664d04d1db3f 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -495,6 +495,8 @@ struct kvm_sync_regs {
 
 #define KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE	0x00000001
 
+#define KVM_STATE_SVM_VALID_GPAT	0x00000001
+
 /* vendor-independent attributes for system fd (group 0) */
 #define KVM_X86_GRP_SYSTEM		0
 #  define KVM_X86_XCOMP_GUEST_SUPP	0
@@ -531,6 +533,9 @@ struct kvm_svm_nested_state_data {
 
 struct kvm_svm_nested_state_hdr {
 	__u64 vmcb_pa;
+	__u32 flags;
+	__u32 reserved;
+	__u64 gpat;
 };
 
 /* for KVM_CAP_NESTED_STATE */
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 26f758e294ab..f73f3e586012 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1893,6 +1893,10 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu,
 	/* First fill in the header and copy it out.  */
 	if (is_guest_mode(vcpu)) {
 		kvm_state.hdr.svm.vmcb_pa = svm->nested.vmcb12_gpa;
+		if (nested_npt_enabled(svm)) {
+			kvm_state.hdr.svm.flags |= KVM_STATE_SVM_VALID_GPAT;
+			kvm_state.hdr.svm.gpat = svm->nested.save.g_pat;
+		}
 		kvm_state.size += KVM_STATE_NESTED_SVM_VMCB_SIZE;
 		kvm_state.flags |= KVM_STATE_NESTED_GUEST_MODE;
 
@@ -2022,6 +2026,14 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 	    !nested_vmcb_check_save(vcpu, &save_cached, false))
 		goto out_free;
 
+	/*
+	 * Validate gPAT, if provided. This is done separately from the
+	 * vmcb_save_area_cached validation above, because gPAT is L2
+	 * state, but the vmcb_save_area_cached is populated with L1 state.
+	 */
+	if ((kvm_state->hdr.svm.flags & KVM_STATE_SVM_VALID_GPAT) &&
+	    !kvm_pat_valid(kvm_state->hdr.svm.gpat))
+		goto out_free;
 
 	/*
 	 * All checks done, we can enter guest mode. Userspace provides
@@ -2061,6 +2073,10 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 	if (ret)
 		goto out_free;
 
+	if (nested_npt_enabled(svm) &&
+	    (kvm_state->hdr.svm.flags & KVM_STATE_SVM_VALID_GPAT))
+		svm_set_gpat(svm, kvm_state->hdr.svm.gpat);
+
 	svm_switch_vmcb(svm, &svm->nested.vmcb02);
 	nested_vmcb02_prepare_control(svm, svm->vmcb->save.rip, svm->vmcb->save.cs.base);
 
-- 
2.53.0.239.g8d8fc8a987-goog