[RFC PATCH 3/5] kvm/svm: Introduce per-CPU lock and wakeup queue

[Sairaj Kodilkar <sarunkod@amd.com>]

Add a per-CPU list and raw spinlock that SVM will use to track vCPUs
blocked and waiting for a wakeup.  The GAPPI interrupt handler will
scan the corresponding CPU’s list to decide which vCPU to run.
Initialize both in avic_hardware_setup() when AVIC is enabled.

Signed-off-by: Sairaj Kodilkar <sarunkod@amd.com>
---
 arch/x86/kvm/svm/avic.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index b666efb5d91c..e7a4c0e90e7a 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -63,6 +63,9 @@
 	ga_tag;								\
 })
 
+static DEFINE_PER_CPU(struct list_head, gappi_vcpu_wakeup_list);
+static DEFINE_PER_CPU(raw_spinlock_t, gappi_vcpu_wakeup_list_lock);
+
 static_assert(__AVIC_GATAG(AVIC_VM_ID_MASK, AVIC_VCPU_IDX_MASK) == -1u);
 
 #define AVIC_AUTO_MODE -1
@@ -1315,12 +1318,18 @@ static bool __init avic_want_avic_enabled(void)
  */
 bool __init avic_hardware_setup(void)
 {
+	int cpu;
 	avic = avic_want_avic_enabled();
 	if (!avic)
 		return false;
 
 	pr_info("AVIC enabled\n");
 
+	for_each_possible_cpu(cpu) {
+		INIT_LIST_HEAD(&per_cpu(gappi_vcpu_wakeup_list, cpu));
+		raw_spin_lock_init(&per_cpu(gappi_vcpu_wakeup_list_lock, cpu));
+	}
+
 	/* AVIC is a prerequisite for x2AVIC. */
 	x2avic_enabled = boot_cpu_has(X86_FEATURE_X2AVIC);
 	if (x2avic_enabled) {
-- 
2.34.1