[PATCH v3 6/8] KVM: x86: nSVM: Save/restore gPAT with KVM_{GET,SET}_NESTED_STATE

[Jim Mattson]

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 gpt field
without changing any offsets.

Fixes: cc440cdad5b7 ("KVM: nSVM: implement KVM_GET_NESTED_STATE and 
KVM_SET_NESTED_STATE")
Signed-off-by: Jim Mattson <jmatt...@google.com>
---
 arch/x86/include/uapi/asm/kvm.h |  5 +++++
 arch/x86/kvm/svm/nested.c       | 14 ++++++++++++++
 2 files changed, 19 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 0b95ae1e864b..3f512fb630db 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1764,6 +1764,10 @@ 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.gpat;
+               }
                kvm_state.size += KVM_STATE_NESTED_SVM_VMCB_SIZE;
                kvm_state.flags |= KVM_STATE_NESTED_GUEST_MODE;
 
@@ -1889,6 +1893,12 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
            !__nested_vmcb_check_save(vcpu, &save_cached))
                goto out_free;
 
+       /*
+        * Validate gPAT, if provided.
+        */
+       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
@@ -1926,6 +1936,10 @@ 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->nested.force_msr_bitmap_recalc = true;
 
        kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
-- 
2.53.0.rc2.204.g2597b5adb4-goog