KVM: SVM: Stuff save->dr6 at during VMSA sync, not at RESET/INIT

Move code to stuff vmcb->save.dr6 to its architectural init value from
svm_vcpu_reset() into sev_es_sync_vmsa().  Except for protected guests,
a.k.a. SEV-ES guests, vmcb->save.dr6 is set during VM-Enter, i.e. the
extra write is unnecessary.  For SEV-ES, stuffing save->dr6 handles a
theoretical case where the VMSA could be encrypted before the first
KVM_RUN.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-33-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/sev.c

@@ -584,6 +584,7 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
 	save->xcr0 = svm->vcpu.arch.xcr0;
 	save->pkru = svm->vcpu.arch.pkru;
 	save->xss  = svm->vcpu.arch.ia32_xss;
+	save->dr6  = svm->vcpu.arch.dr6;
 
 	/*
 	 * SEV-ES will use a VMSA that is pointed to by the VMCB, not

arch/x86/kvm/svm/svm.c

@@ -1252,7 +1252,6 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
 	svm_set_cr0(vcpu, X86_CR0_NW | X86_CR0_CD | X86_CR0_ET);
 	svm_set_cr4(vcpu, 0);
 	svm_set_efer(vcpu, 0);
-	save->dr6 = 0xffff0ff0;
 	kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
 	vcpu->arch.regs[VCPU_REGS_RIP] = 0x0000fff0;