[PATCH v8 5/8] KVM: x86: Carve out common dirty logging update

[Nikunj A Dadhania <nikunj@amd.com>]

Move the PML enable/disable decision logic from the VMX into a new
common wrapper kvm_update_cpu_dirty_logging() in x86.c to avoid
code duplication. Update the update_cpu_dirty_logging() signature to
accept a bool enable parameter accordingly.

Note, this subtly changes the ordering for VMX: currently
guard(vmx_vmcs01) is taken before the atomic_read of
nr_memslots_dirty_logging; after this refactoring the atomic_read
happens in common code before guard(vmx_vmcs01) is taken. The ordering
flip is harmless as a concurrent change to nr_memslots_dirty_logging
will queue another update request.

No functional change intended for VMX, restructuring to prepare for SVM
PML support.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/vmx/main.c         |  4 ++--
 arch/x86/kvm/vmx/vmx.c          | 12 ++----------
 arch/x86/kvm/vmx/vmx.h          |  2 +-
 arch/x86/kvm/vmx/x86_ops.h      |  2 +-
 arch/x86/kvm/x86.c              | 17 ++++++++++++++++-
 6 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 07c422793702..2debf6294290 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1672,7 +1672,7 @@ struct kvm_x86_ops {
 			       struct x86_exception *exception);
 	void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu);
 
-	void (*update_cpu_dirty_logging)(struct kvm_vcpu *vcpu);
+	void (*update_cpu_dirty_logging)(struct kvm_vcpu *vcpu, bool enable);
 
 	void (*vcpu_blocking)(struct kvm_vcpu *vcpu);
 	void (*vcpu_unblocking)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index 4c52ab8d0786..e77b5b731275 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -108,7 +108,7 @@ static void vt_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	vmx_vcpu_load(vcpu, cpu);
 }
 
-static void vt_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
+static void vt_update_cpu_dirty_logging(struct kvm_vcpu *vcpu, bool enable)
 {
 	/*
 	 * Basic TDX does not support feature PML. KVM does not enable PML in
@@ -117,7 +117,7 @@ static void vt_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
 	if (WARN_ON_ONCE(is_td_vcpu(vcpu)))
 		return;
 
-	vmx_update_cpu_dirty_logging(vcpu);
+	vmx_update_cpu_dirty_logging(vcpu, enable);
 }
 
 static void vt_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d944ea9ed273..b3768b4b212f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8418,21 +8418,13 @@ static void vmx_update_hv_timer(struct kvm_vcpu *vcpu, bool force_immediate_exit
 }
 #endif
 
-void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
+void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu, bool enable)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-	if (WARN_ON_ONCE(!vcpu->kvm->arch.cpu_dirty_log_size))
-		return;
-
 	guard(vmx_vmcs01)(vcpu);
 
-	/*
-	 * Note, nr_memslots_dirty_logging can be changed concurrent with this
-	 * code, but in that case another update request will be made and so
-	 * the guest will never run with a stale PML value.
-	 */
-	if (atomic_read(&vcpu->kvm->nr_memslots_dirty_logging))
+	if (enable)
 		secondary_exec_controls_setbit(vmx, SECONDARY_EXEC_ENABLE_PML);
 	else
 		secondary_exec_controls_clearbit(vmx, SECONDARY_EXEC_ENABLE_PML);
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 6bcca3487c59..5f505ad14dde 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -390,7 +390,7 @@ u64 vmx_get_l2_tsc_multiplier(struct kvm_vcpu *vcpu);
 
 gva_t vmx_get_untagged_addr(struct kvm_vcpu *vcpu, gva_t gva, unsigned int flags);
 
-void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu);
+void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu, bool enable);
 
 u64 vmx_get_supported_debugctl(struct kvm_vcpu *vcpu, bool host_initiated);
 bool vmx_is_valid_debugctl(struct kvm_vcpu *vcpu, u64 data, bool host_initiated);
diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
index 054fd14bb2e1..4810f9b1b0fc 100644
--- a/arch/x86/kvm/vmx/x86_ops.h
+++ b/arch/x86/kvm/vmx/x86_ops.h
@@ -118,7 +118,7 @@ u64 vmx_get_l2_tsc_offset(struct kvm_vcpu *vcpu);
 u64 vmx_get_l2_tsc_multiplier(struct kvm_vcpu *vcpu);
 void vmx_write_tsc_offset(struct kvm_vcpu *vcpu);
 void vmx_write_tsc_multiplier(struct kvm_vcpu *vcpu);
-void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu);
+void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu, bool enable);
 #ifdef CONFIG_X86_64
 int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc,
 		     bool *expired);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dc5af51c0a90..6d26de8b7c3c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8073,6 +8073,21 @@ static void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
 	kvm_x86_call(set_apic_access_page_addr)(vcpu);
 }
 
+static void kvm_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * Note, nr_memslots_dirty_logging can be changed concurrent with this
+	 * code, but in that case another update request will be made and so
+	 * the guest will never run with a stale PML value.
+	 */
+	bool enable = atomic_read(&vcpu->kvm->nr_memslots_dirty_logging);
+
+	if (WARN_ON_ONCE(!vcpu->kvm->arch.cpu_dirty_log_size))
+		return;
+
+	kvm_x86_call(update_cpu_dirty_logging)(vcpu, enable);
+}
+
 /*
  * Called within kvm->srcu read side.
  * Returns 1 to let vcpu_run() continue the guest execution loop without
@@ -8239,7 +8254,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			kvm_x86_call(recalc_intercepts)(vcpu);
 
 		if (kvm_check_request(KVM_REQ_UPDATE_CPU_DIRTY_LOGGING, vcpu))
-			kvm_x86_call(update_cpu_dirty_logging)(vcpu);
+			kvm_update_cpu_dirty_logging(vcpu);
 
 		if (kvm_check_request(KVM_REQ_UPDATE_PROTECTED_GUEST_STATE, vcpu)) {
 			kvm_vcpu_reset(vcpu, true);
-- 
2.48.1