From 46336eed191fea4f326075f06e7dbb64f982f1db Mon Sep 17 00:00:00 2001
From: Zeng Guang <guang.zeng@intel.com>
Date: Thu, 25 Aug 2022 10:52:46 +0800
Subject: [PATCH 1103/1119] target/i386: Set maximum APIC ID to KVM prior to
 vCPU creation

commit 19e2a9fb9da067acba95b3be83588bda5a3f6a99 upstream.

Specify maximum possible APIC ID assigned for current VM session to KVM
prior to the creation of vCPUs. By this setting, KVM can set up VM-scoped
data structure indexed by the APIC ID, e.g. Posted-Interrupt Descriptor
pointer table to support Intel IPI virtualization, with the most optimal
memory footprint.

It can be achieved by calling KVM_ENABLE_CAP for KVM_CAP_MAX_VCPU_ID
capability once KVM has enabled it. Ignoring the return error if KVM
doesn't support this capability yet.

Intel-SIG: commit 19e2a9fb9da0 ("target/i386: Set maximum APIC ID to KVM prior to vCPU creation").
Backport setting maximum APIC ID for qemu-6.2.0

Signed-off-by: Zeng Guang <guang.zeng@intel.com>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20220825025246.26618-1-guang.zeng@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[ jason: amend commit log ]
Signed-off-by: Jason Zeng <jason.zeng@intel.com>
---
 hw/i386/x86.c              | 4 ++++
 target/i386/kvm/kvm-stub.c | 5 +++++
 target/i386/kvm/kvm.c      | 5 +++++
 target/i386/kvm/kvm_i386.h | 2 ++
 4 files changed, 16 insertions(+)

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index f64639b8731c..a3258d78facf 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -152,6 +152,10 @@ void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)
         exit(EXIT_FAILURE);
     }
 
+    if (kvm_enabled()) {
+        kvm_set_max_apic_id(x86ms->apic_id_limit);
+    }
+
     possible_cpus = mc->possible_cpu_arch_ids(ms);
     for (i = 0; i < ms->smp.cpus; i++) {
         x86_cpu_new(x86ms, possible_cpus->cpus[i].arch_id, &error_fatal);
diff --git a/target/i386/kvm/kvm-stub.c b/target/i386/kvm/kvm-stub.c
index f6e7e4466e1a..e052f1c7b0ef 100644
--- a/target/i386/kvm/kvm-stub.c
+++ b/target/i386/kvm/kvm-stub.c
@@ -44,3 +44,8 @@ bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
 {
     abort();
 }
+
+void kvm_set_max_apic_id(uint32_t max_apic_id)
+{
+    return;
+}
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index ae50575edc7e..43187699456c 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -5526,3 +5526,8 @@ void kvm_arch_accel_class_init(ObjectClass *oc)
                                           "Clock cycles without an event window "
                                           "after which a notification VM exit occurs");
 }
+
+void kvm_set_max_apic_id(uint32_t max_apic_id)
+{
+    kvm_vm_enable_cap(kvm_state, KVM_CAP_MAX_VCPU_ID, 0, max_apic_id);
+}
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 2ed586c11b7e..23f6cab60017 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -65,4 +65,6 @@ typedef struct kvm_msr_handlers {
 bool kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
                     QEMUWRMSRHandler *wrmsr);
 
+void kvm_set_max_apic_id(uint32_t max_apic_id);
+
 #endif
-- 
2.33.0