KVM: SVM: Truncate GPR value for DR and CR accesses in !64-bit mode

commit 0884335 upstream.

Drop bits 63:32 on loads/stores to/from DRs and CRs when the vCPU is not
in 64-bit mode.  The APM states bits 63:32 are dropped for both DRs and
CRs:

  In 64-bit mode, the operand size is fixed at 64 bits without the need
  for a REX prefix. In non-64-bit mode, the operand size is fixed at 32
  bits and the upper 32 bits of the destination are forced to 0.

Fixes: 7ff76d5 ("KVM: SVM: enhance MOV CR intercept handler")
Fixes: cae3797 ("KVM: SVM: enhance mov DR intercept handler")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210422022128.3464144-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[sudip: manual backport to old file]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kvm/svm.c

@@ -4033,7 +4033,7 @@ static int cr_interception(struct vcpu_svm *svm)
 	err = 0;
 	if (cr >= 16) { /* mov to cr */
 		cr -= 16;
-		val = kvm_register_read(&svm->vcpu, reg);
+		val = kvm_register_readl(&svm->vcpu, reg);
 		switch (cr) {
 		case 0:
 			if (!check_selective_cr0_intercepted(svm, val))
@@ -4078,7 +4078,7 @@ static int cr_interception(struct vcpu_svm *svm)
 			kvm_queue_exception(&svm->vcpu, UD_VECTOR);
 			return 1;
 		}
-		kvm_register_write(&svm->vcpu, reg, val);
+		kvm_register_writel(&svm->vcpu, reg, val);
 	}
 	return kvm_complete_insn_gp(&svm->vcpu, err);
 }
@@ -4108,13 +4108,13 @@ static int dr_interception(struct vcpu_svm *svm)
 	if (dr >= 16) { /* mov to DRn */
 		if (!kvm_require_dr(&svm->vcpu, dr - 16))
 			return 1;
-		val = kvm_register_read(&svm->vcpu, reg);
+		val = kvm_register_readl(&svm->vcpu, reg);
 		kvm_set_dr(&svm->vcpu, dr - 16, val);
 	} else {
 		if (!kvm_require_dr(&svm->vcpu, dr))
 			return 1;
 		kvm_get_dr(&svm->vcpu, dr, &val);
-		kvm_register_write(&svm->vcpu, reg, val);
+		kvm_register_writel(&svm->vcpu, reg, val);
 	}
 
 	return kvm_skip_emulated_instruction(&svm->vcpu);