[Qemu-devel] [PATCH 2/2] i386/kvm: add support for Hyper-V IPI send

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Hyper-V PV IPI support is merged to KVM, enable the feature in Qemu. When
enabled, this allows Windows guests to send IPIs to other vCPUs with a
single hypercall even when there are >64 vCPUs in the request.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 target/i386/cpu.c          |  1 +
 target/i386/cpu.h          |  1 +
 target/i386/hyperv-proto.h |  1 +
 target/i386/kvm.c          | 14 +++++++++++++-
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index c88876dfe3..32ea041c06 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5564,6 +5564,7 @@ static Property x86_cpu_properties[] = {
     DEFINE_PROP_BOOL("hv-frequencies", X86CPU, hyperv_frequencies, false),
     DEFINE_PROP_BOOL("hv-reenlightenment", X86CPU, hyperv_reenlightenment, false),
     DEFINE_PROP_BOOL("hv-tlbflush", X86CPU, hyperv_tlbflush, false),
+    DEFINE_PROP_BOOL("hv-ipi", X86CPU, hyperv_ipi, false),
     DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true),
     DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
     DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 730c06f80a..caa1544b2e 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1382,6 +1382,7 @@ struct X86CPU {
     bool hyperv_frequencies;
     bool hyperv_reenlightenment;
     bool hyperv_tlbflush;
+    bool hyperv_ipi;
     bool check_cpuid;
     bool enforce_cpuid;
     bool expose_kvm;
diff --git a/target/i386/hyperv-proto.h b/target/i386/hyperv-proto.h
index d6d5a79293..87f36d14e8 100644
--- a/target/i386/hyperv-proto.h
+++ b/target/i386/hyperv-proto.h
@@ -58,6 +58,7 @@
 #define HV_APIC_ACCESS_RECOMMENDED          (1u << 3)
 #define HV_SYSTEM_RESET_RECOMMENDED         (1u << 4)
 #define HV_RELAXED_TIMING_RECOMMENDED       (1u << 5)
+#define HV_CLUSTER_IPI_RECOMMENDED          (1u << 10)
 #define HV_EX_PROCESSOR_MASKS_RECOMMENDED   (1u << 11)
 
 /*
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index dc4047b02f..795aa52938 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -608,7 +608,8 @@ static bool hyperv_enabled(X86CPU *cpu)
             cpu->hyperv_synic ||
             cpu->hyperv_stimer ||
             cpu->hyperv_reenlightenment ||
-            cpu->hyperv_tlbflush);
+            cpu->hyperv_tlbflush ||
+            cpu->hyperv_ipi);
 }
 
 static int kvm_arch_set_tsc_khz(CPUState *cs)
@@ -888,6 +889,17 @@ int kvm_arch_init_vcpu(CPUState *cs)
             c->eax |= HV_REMOTE_TLB_FLUSH_RECOMMENDED;
             c->eax |= HV_EX_PROCESSOR_MASKS_RECOMMENDED;
         }
+        if (cpu->hyperv_ipi) {
+            if (kvm_check_extension(cs->kvm_state,
+                                    KVM_CAP_HYPERV_SEND_IPI) <= 0) {
+                fprintf(stderr, "Hyper-V IPI send support "
+                        "(requested by 'hv-ipi' cpu flag) "
+                        " is not supported by kernel\n");
+                return -ENOSYS;
+            }
+            c->eax |= HV_CLUSTER_IPI_RECOMMENDED;
+            c->eax |= HV_EX_PROCESSOR_MASKS_RECOMMENDED;
+        }
 
         c->ebx = cpu->hyperv_spinlock_attempts;
 
-- 
2.17.1