KVM: VMX: refactor PML terminology

Rename PML_ENTITY_NUM to PML_LOG_NR_ENTRIES
Add PML_HEAD_INDEX to specify the first entry that CPU writes.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20241219221034.903927-2-mlevitsk@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: Maxim Levitsky

arch/x86/kvm/vmx/main.c

@@ -125,7 +125,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.check_intercept = vmx_check_intercept,
 	.handle_exit_irqoff = vmx_handle_exit_irqoff,
 
-	.cpu_dirty_log_size = PML_ENTITY_NUM,
+	.cpu_dirty_log_size = PML_LOG_NR_ENTRIES,
 	.update_cpu_dirty_logging = vmx_update_cpu_dirty_logging,
 
 	.nested_ops = &vmx_nested_ops,

arch/x86/kvm/vmx/nested.c

@@ -3442,7 +3442,7 @@ static int nested_vmx_write_pml_buffer(struct kvm_vcpu *vcpu, gpa_t gpa)
 	if (!nested_cpu_has_pml(vmcs12))
 		return 0;
 
-	if (vmcs12->guest_pml_index >= PML_ENTITY_NUM) {
+	if (vmcs12->guest_pml_index >= PML_LOG_NR_ENTRIES) {
 		vmx->nested.pml_full = true;
 		return 1;
 	}

arch/x86/kvm/vmx/vmx.c

@@ -4821,7 +4821,7 @@ static void init_vmcs(struct vcpu_vmx *vmx)
 
 	if (enable_pml) {
 		vmcs_write64(PML_ADDRESS, page_to_phys(vmx->pml_pg));
-		vmcs_write16(GUEST_PML_INDEX, PML_ENTITY_NUM - 1);
+		vmcs_write16(GUEST_PML_INDEX, PML_HEAD_INDEX);
 	}
 
 	vmx_write_encls_bitmap(&vmx->vcpu, NULL);
@@ -6209,17 +6209,17 @@ static void vmx_flush_pml_buffer(struct kvm_vcpu *vcpu)
 	pml_idx = vmcs_read16(GUEST_PML_INDEX);
 
 	/* Do nothing if PML buffer is empty */
-	if (pml_idx == (PML_ENTITY_NUM - 1))
+	if (pml_idx == PML_HEAD_INDEX)
 		return;
 
 	/* PML index always points to next available PML buffer entity */
-	if (pml_idx >= PML_ENTITY_NUM)
+	if (pml_idx >= PML_LOG_NR_ENTRIES)
 		pml_idx = 0;
 	else
 		pml_idx++;
 
 	pml_buf = page_address(vmx->pml_pg);
-	for (; pml_idx < PML_ENTITY_NUM; pml_idx++) {
+	for (; pml_idx < PML_LOG_NR_ENTRIES; pml_idx++) {
 		u64 gpa;
 
 		gpa = pml_buf[pml_idx];
@@ -6228,7 +6228,7 @@ static void vmx_flush_pml_buffer(struct kvm_vcpu *vcpu)
 	}
 
 	/* reset PML index */
-	vmcs_write16(GUEST_PML_INDEX, PML_ENTITY_NUM - 1);
+	vmcs_write16(GUEST_PML_INDEX, PML_HEAD_INDEX);
 }
 
 static void vmx_dump_sel(char *name, uint32_t sel)

arch/x86/kvm/vmx/vmx.h

@@ -331,7 +331,10 @@ struct vcpu_vmx {
 	bool ple_window_dirty;
 
 	/* Support for PML */
-#define PML_ENTITY_NUM		512
+#define PML_LOG_NR_ENTRIES	512
+	/* PML is written backwards: this is the first entry written by the CPU */
+#define PML_HEAD_INDEX		(PML_LOG_NR_ENTRIES-1)
+
 	struct page *pml_pg;
 
 	/* apic deadline value in host tsc */