[Qemu-devel] [PATCH] i386/kvm: add support for Hyper-V TLB flush

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Add support for Hyper-V TLB flush which recently got added to KVM.

Just like regular Hyper-V we announce HV_EX_PROCESSOR_MASKS_RECOMMENDED
regardless of how many vCPUs we have. Windows is 'smart' and uses less
expensive non-EX Hypercall whenever possible (when it wants to flush TLB
for all vCPUs or the maximum vCPU index in the vCPU set requires flushing
is less than 64).

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 linux-headers/linux/kvm.h  |  1 +
 target/i386/cpu.c          |  1 +
 target/i386/cpu.h          |  1 +
 target/i386/hyperv-proto.h |  1 +
 target/i386/kvm.c          | 15 ++++++++++++++-
 5 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index cdb148e959..a52a685690 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -948,6 +948,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_S390_BPB 152
 #define KVM_CAP_GET_MSR_FEATURES 153
 #define KVM_CAP_HYPERV_EVENTFD 154
+#define KVM_CAP_HYPERV_TLBFLUSH 155
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 94260412e2..756cc78808 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5151,6 +5151,7 @@ static Property x86_cpu_properties[] = {
     DEFINE_PROP_BOOL("hv-stimer", X86CPU, hyperv_stimer, false),
     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("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 664504610e..738d695331 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1363,6 +1363,7 @@ struct X86CPU {
     bool hyperv_stimer;
     bool hyperv_frequencies;
     bool hyperv_reenlightenment;
+    bool hyperv_tlbflush;
     bool check_cpuid;
     bool enforce_cpuid;
     bool expose_kvm;
diff --git a/target/i386/hyperv-proto.h b/target/i386/hyperv-proto.h
index 93352ebd2a..d6d5a79293 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_EX_PROCESSOR_MASKS_RECOMMENDED   (1u << 11)
 
 /*
  * Basic virtualized MSRs
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 44f70733e7..91c8e952c8 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -585,7 +585,8 @@ static bool hyperv_enabled(X86CPU *cpu)
             cpu->hyperv_runtime ||
             cpu->hyperv_synic ||
             cpu->hyperv_stimer ||
-            cpu->hyperv_reenlightenment);
+            cpu->hyperv_reenlightenment ||
+            cpu->hyperv_tlbflush);
 }
 
 static int kvm_arch_set_tsc_khz(CPUState *cs)
@@ -823,6 +824,18 @@ int kvm_arch_init_vcpu(CPUState *cs)
         if (cpu->hyperv_vapic) {
             c->eax |= HV_APIC_ACCESS_RECOMMENDED;
         }
+        if (cpu->hyperv_tlbflush) {
+            if (kvm_check_extension(cs->kvm_state,
+                                    KVM_CAP_HYPERV_TLBFLUSH) <= 0) {
+                fprintf(stderr, "Hyper-V TLB flush support "
+                        "(requested by 'hv-tlbflush' cpu flag) "
+                        " is not supported by kernel\n");
+                return -ENOSYS;
+            }
+            c->eax |= HV_REMOTE_TLB_FLUSH_RECOMMENDED;
+            c->eax |= HV_EX_PROCESSOR_MASKS_RECOMMENDED;
+        }
+
         c->ebx = cpu->hyperv_spinlock_attempts;
 
         c = &cpuid_data.entries[cpuid_i++];
-- 
2.14.4