[PATCH 2/5] nSVM: Check for optional commands and reserved encodings of TLB_CONTROL in nested VMCB

[Krish Sadhukhan <krish.sadhukhan@oracle.com>]

According to section "TLB Flush" in APM vol 2,

    "Support for TLB_CONTROL commands other than the first two, is
     optional and is indicated by CPUID Fn8000_000A_EDX[FlushByAsid].

     All encodings of TLB_CONTROL not defined in the APM are reserved."

Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
---
 arch/x86/kvm/svm/nested.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 5e13357da21e..028cc2a1f028 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -235,6 +235,22 @@ static bool nested_svm_check_bitmap_pa(struct kvm_vcpu *vcpu, u64 pa, u32 size)
 	    kvm_vcpu_is_legal_gpa(vcpu, addr + size - 1);
 }
 
+static bool nested_svm_check_tlb_ctl(struct kvm_vcpu *vcpu, u8 tlb_ctl)
+{
+	switch(tlb_ctl) {
+		case TLB_CONTROL_DO_NOTHING:
+		case TLB_CONTROL_FLUSH_ALL_ASID:
+			return true;
+		case TLB_CONTROL_FLUSH_ASID:
+		case TLB_CONTROL_FLUSH_ASID_LOCAL:
+			if (guest_cpuid_has(vcpu, X86_FEATURE_FLUSHBYASID))
+				return true;
+			fallthrough;
+		default:
+			return false;
+	}
+}
+
 static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 				       struct vmcb_control_area *control)
 {
@@ -254,6 +270,9 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
 					   IOPM_SIZE)))
 		return false;
 
+	if (CC(!nested_svm_check_tlb_ctl(vcpu, control->tlb_ctl)))
+		return false;
+
 	return true;
 }
 
-- 
2.27.0