[PATCH v3 4/5] KVM: SVM: Compute DEBUGCTL reserved bits dynamically

[Shivansh Dhiman <shivansh.dhiman@amd.com>]

Replace the static DEBUGCTL_RESERVED_BITS macro with a helper,
svm_get_debugctl_reserved_bits(), that derives the reserved bits from the
guest's CPUID. This will allow DEBUGCTLMSR_BUS_LOCK_DETECT only when the
guest supports Bus Lock Detect, on both the MSR write and nested load
paths.

Plumb the vCPU into svm_copy_vmrun_state() so it can pass it to the helper.

Co-developed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
---
Changelog:
v3:
 * New patch.
 * Replaced the static DEBUGCTL_RESERVED_BITS macro with a per-vCPU helper
   that gates the bit on guest CPUID.

---
 arch/x86/kvm/svm/nested.c |  8 ++++----
 arch/x86/kvm/svm/svm.c    |  6 +++---
 arch/x86/kvm/svm/svm.h    | 12 ++++++++++--
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 0a9e28a02692..4dfccc2deda8 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -821,7 +821,7 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm)
 		 * svm_set_msr's definition of reserved bits.
 		 */
 		svm_copy_lbrs(&vmcb02->save, save);
-		vmcb02->save.dbgctl &= ~DEBUGCTL_RESERVED_BITS;
+		vmcb02->save.dbgctl &= ~svm_get_debugctl_reserved_bits(vcpu);
 	} else {
 		svm_copy_lbrs(&vmcb02->save, &vmcb01->save);
 	}
@@ -1204,7 +1204,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 }
 
 /* Copy state save area fields which are handled by VMRUN */
-void svm_copy_vmrun_state(struct vmcb_save_area *to_save,
+void svm_copy_vmrun_state(struct kvm_vcpu *vcpu, struct vmcb_save_area *to_save,
 			  struct vmcb_save_area *from_save)
 {
 	to_save->es = from_save->es;
@@ -1231,7 +1231,7 @@ void svm_copy_vmrun_state(struct vmcb_save_area *to_save,
 
 	if (kvm_cpu_cap_has(X86_FEATURE_LBRV)) {
 		svm_copy_lbrs(to_save, from_save);
-		to_save->dbgctl &= ~DEBUGCTL_RESERVED_BITS;
+		to_save->dbgctl &= ~svm_get_debugctl_reserved_bits(vcpu);
 	}
 }
 
@@ -2072,7 +2072,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 
 	svm->nested.vmcb12_gpa = kvm_state->hdr.svm.vmcb_pa;
 
-	svm_copy_vmrun_state(&svm->vmcb01.ptr->save, save);
+	svm_copy_vmrun_state(vcpu, &svm->vmcb01.ptr->save, save);
 	nested_copy_vmcb_control_to_cache(svm, ctl);
 
 	svm_switch_vmcb(svm, &svm->nested.vmcb02);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index cead8f99d856..a59389c322da 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3164,7 +3164,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 			data &= ~DEBUGCTLMSR_BTF;
 		}
 
-		if (data & DEBUGCTL_RESERVED_BITS)
+		if (data & svm_get_debugctl_reserved_bits(vcpu))
 			return 1;
 
 		if (svm->vmcb->save.dbgctl == data)
@@ -5037,7 +5037,7 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
 
 	BUILD_BUG_ON(offsetof(struct vmcb, save) != 0x400);
 
-	svm_copy_vmrun_state(map_save.hva + 0x400,
+	svm_copy_vmrun_state(vcpu, map_save.hva + 0x400,
 			     &svm->vmcb01.ptr->save);
 
 	kvm_vcpu_unmap(vcpu, &map_save);
@@ -5081,7 +5081,7 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
 	 * used during SMM (see svm_enter_smm())
 	 */
 
-	svm_copy_vmrun_state(&svm->vmcb01.ptr->save, map_save.hva + 0x400);
+	svm_copy_vmrun_state(vcpu, &svm->vmcb01.ptr->save, map_save.hva + 0x400);
 
 	/*
 	 * Enter the nested guest now
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 8d77c10cf4f6..402a827f622d 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -783,7 +783,15 @@ BUILD_SVM_MSR_BITMAP_HELPERS(bool, test, test)
 BUILD_SVM_MSR_BITMAP_HELPERS(void, clear, __clear)
 BUILD_SVM_MSR_BITMAP_HELPERS(void, set, __set)
 
-#define DEBUGCTL_RESERVED_BITS (~DEBUGCTLMSR_LBR)
+static inline u64 svm_get_debugctl_reserved_bits(struct kvm_vcpu *vcpu)
+{
+	u64 debugctl = DEBUGCTLMSR_LBR;
+
+	if (guest_cpu_cap_has(vcpu, X86_FEATURE_BUS_LOCK_DETECT))
+		debugctl |= DEBUGCTLMSR_BUS_LOCK_DETECT;
+
+	return ~debugctl;
+}
 
 /* svm.c */
 extern bool dump_invalid_vmcb;
@@ -873,7 +881,7 @@ void svm_leave_nested(struct kvm_vcpu *vcpu);
 void svm_free_nested(struct vcpu_svm *svm);
 int svm_allocate_nested(struct vcpu_svm *svm);
 int nested_svm_vmrun(struct kvm_vcpu *vcpu);
-void svm_copy_vmrun_state(struct vmcb_save_area *to_save,
+void svm_copy_vmrun_state(struct kvm_vcpu *vcpu, struct vmcb_save_area *to_save,
 			  struct vmcb_save_area *from_save);
 void svm_copy_vmloadsave_state(struct vmcb *to_vmcb, struct vmcb *from_vmcb);
 void nested_svm_vmexit(struct vcpu_svm *svm);
-- 
2.43.0