Store each "disabled exit" boolean in a single bit rather than a byte.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/include/asm/kvm_host.h |  5 +----
 arch/x86/kvm/svm/svm.c          |  2 +-
 arch/x86/kvm/vmx/vmx.c          |  2 +-
 arch/x86/kvm/x86.c              |  8 ++++----
 arch/x86/kvm/x86.h              | 13 +++++++++----
 5 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 67b464651c8d..fa912b2e7591 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1390,10 +1390,7 @@ struct kvm_arch {
 
 	gpa_t wall_clock;
 
-	bool mwait_in_guest;
-	bool hlt_in_guest;
-	bool pause_in_guest;
-	bool cstate_in_guest;
+	u64 disabled_exits;
 
 	unsigned long irq_sources_bitmap;
 	s64 kvmclock_offset;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ffb34dadff1c..6d2d97fd967a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5102,7 +5102,7 @@ static int svm_vm_init(struct kvm *kvm)
 	}
 
 	if (!pause_filter_count || !pause_filter_thresh)
-		kvm->arch.pause_in_guest = true;
+		kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_PAUSE);
 
 	if (enable_apicv) {
 		int ret = avic_vm_init(kvm);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b12414108cbf..136be14e6db0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7619,7 +7619,7 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
 int vmx_vm_init(struct kvm *kvm)
 {
 	if (!ple_gap)
-		kvm->arch.pause_in_guest = true;
+		kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_PAUSE);
 
 	if (boot_cpu_has(X86_BUG_L1TF) && enable_ept) {
 		switch (l1tf_mitigation) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 570e7f8cbf64..8c20afda4398 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6605,13 +6605,13 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 			pr_warn_once(SMT_RSB_MSG);
 
 		if (cap->args[0] & KVM_X86_DISABLE_EXITS_PAUSE)
-			kvm->arch.pause_in_guest = true;
+			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_PAUSE);
 		if (cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT)
-			kvm->arch.mwait_in_guest = true;
+			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_MWAIT);
 		if (cap->args[0] & KVM_X86_DISABLE_EXITS_HLT)
-			kvm->arch.hlt_in_guest = true;
+			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_HLT);
 		if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE)
-			kvm->arch.cstate_in_guest = true;
+			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_CSTATE);
 		r = 0;
 disable_exits_unlock:
 		mutex_unlock(&kvm->lock);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 88a9475899c8..0ad36851df4c 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -481,24 +481,29 @@ static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec)
 	    __rem;						\
 	 })
 
+static inline void kvm_disable_exits(struct kvm *kvm, u64 mask)
+{
+	kvm->arch.disabled_exits |= mask;
+}
+
 static inline bool kvm_mwait_in_guest(struct kvm *kvm)
 {
-	return kvm->arch.mwait_in_guest;
+	return kvm->arch.disabled_exits & KVM_X86_DISABLE_EXITS_MWAIT;
 }
 
 static inline bool kvm_hlt_in_guest(struct kvm *kvm)
 {
-	return kvm->arch.hlt_in_guest;
+	return kvm->arch.disabled_exits & KVM_X86_DISABLE_EXITS_HLT;
 }
 
 static inline bool kvm_pause_in_guest(struct kvm *kvm)
 {
-	return kvm->arch.pause_in_guest;
+	return kvm->arch.disabled_exits & KVM_X86_DISABLE_EXITS_PAUSE;
 }
 
 static inline bool kvm_cstate_in_guest(struct kvm *kvm)
 {
-	return kvm->arch.cstate_in_guest;
+	return kvm->arch.disabled_exits & KVM_X86_DISABLE_EXITS_CSTATE;
 }
 
 static inline bool kvm_notify_vmexit_enabled(struct kvm *kvm)
-- 
2.49.0.1204.g71687c7c1d-goog

On Fri, May 30, 2025, Jim Mattson wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 570e7f8cbf64..8c20afda4398 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6605,13 +6605,13 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>  			pr_warn_once(SMT_RSB_MSG);
>  
>  		if (cap->args[0] & KVM_X86_DISABLE_EXITS_PAUSE)
> -			kvm->arch.pause_in_guest = true;
> +			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_PAUSE);
>  		if (cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT)
> -			kvm->arch.mwait_in_guest = true;
> +			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_MWAIT);
>  		if (cap->args[0] & KVM_X86_DISABLE_EXITS_HLT)
> -			kvm->arch.hlt_in_guest = true;
> +			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_HLT);
>  		if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE)
> -			kvm->arch.cstate_in_guest = true;
> +			kvm_disable_exits(kvm, KVM_X86_DISABLE_EXITS_CSTATE);
>  		r = 0;
>  disable_exits_unlock:
>  		mutex_unlock(&kvm->lock);

Can't this simply be?  The set of capabilities to disable has already been vetted,
so I don't see any reason to manually process each flag.

		mutex_lock(&kvm->lock);
		if (kvm->created_vcpus)
			goto disable_exits_unlock;

#define SMT_RSB_MSG "This processor is affected by the Cross-Thread Return Predictions vulnerability. " \
		    "KVM_CAP_X86_DISABLE_EXITS should only be used with SMT disabled or trusted guests."

		if (!mitigate_smt_rsb && boot_cpu_has_bug(X86_BUG_SMT_RSB) &&
		    cpu_smt_possible() &&
		    (cap->args[0] & ~(KVM_X86_DISABLE_EXITS_PAUSE |
				      KVM_X86_DISABLE_EXITS_APERFMPERF)))
			pr_warn_once(SMT_RSB_MSG);

		kvm_disable_exits(kvm, cap->args[0]);
		r = 0;
disable_exits_unlock:
		mutex_unlock(&kvm->lock);
		break;

On Tue, Jun 24, 2025 at 2:25 PM Sean Christopherson <seanjc@google.com> wrote:
> Can't this simply be?  The set of capabilities to disable has already been vetted,
> so I don't see any reason to manually process each flag.

I love it! Thank you.