From: Tianyu Lan <tianyu....@microsoft.com>
Hyper-V direct tlb flush targets KVM on Hyper-V guest.
Enable direct TLB flush for its guests meaning that TLB
flush hypercalls are handled by Level 0 hypervisor (Hyper-V)
bypassing KVM in Level 1. Due to the different ABI for hypercall
parameters between Hyper-V and KVM, KVM capabilities should be
hidden when enable Hyper-V direct tlb flush otherwise KVM
hypercalls may be intercepted by Hyper-V. Add new parameter
"hv-direct-tlbflush". Check expose_kvm and Hyper-V tlb flush
capability status before enabling the feature.
Signed-off-by: Tianyu Lan <tianyu....@microsoft.com>
---
docs/hyperv.txt | 12 ++++++++++++
linux-headers/linux/kvm.h | 1 +
target/i386/cpu.c | 2 ++
target/i386/cpu.h | 1 +
target/i386/kvm.c | 21 +++++++++++++++++++++
5 files changed, 37 insertions(+)
diff --git a/docs/hyperv.txt b/docs/hyperv.txt
index 8fdf25c829..ceab8c21fe 100644
--- a/docs/hyperv.txt
+++ b/docs/hyperv.txt
@@ -184,6 +184,18 @@ enabled.
Requires: hv-vpindex, hv-synic, hv-time, hv-stimer
+3.18. hv-direct-tlbflush
+=======================
+The enlightenment targets KVM on Hyper-V guest. Enable direct TLB flush for
+its guests meaning that TLB flush hypercalls are handled by Level 0 hypervisor
+(Hyper-V) bypassing KVM in Level 1. Due to the different ABI for hypercall
+parameters between Hyper-V and KVM, enabling this capability effectively
+disables all hypercall handling by KVM (as some KVM hypercall may be mistakenly
+treated as TLB flush hypercalls by Hyper-V). So kvm capability should not show
+to guest when enable this capability. If not, user will fail to enable this
+capability.
+
+Requires: hv-tlbflush, -kvm
4. Development features
========================
diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index 18892d6541..923fb33a01 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -995,6 +995,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_ARM_SVE 170
#define KVM_CAP_ARM_PTRAUTH_ADDRESS 171
#define KVM_CAP_ARM_PTRAUTH_GENERIC 172
+#define KVM_CAP_HYPERV_DIRECT_TLBFLUSH 174
#ifdef KVM_CAP_IRQ_ROUTING
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 44f1bbdcac..7bc7fee512 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6156,6 +6156,8 @@ static Property x86_cpu_properties[] = {
HYPERV_FEAT_IPI, 0),
DEFINE_PROP_BIT64("hv-stimer-direct", X86CPU, hyperv_features,
HYPERV_FEAT_STIMER_DIRECT, 0),
+ DEFINE_PROP_BIT64("hv-direct-tlbflush", X86CPU, hyperv_features,
+ HYPERV_FEAT_DIRECT_TLBFLUSH, 0),
DEFINE_PROP_BOOL("hv-passthrough", X86CPU, hyperv_passthrough, false),
DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true),
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index eaa5395aa5..3cb105f7d6 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -907,6 +907,7 @@ typedef uint64_t FeatureWordArray[FEATURE_WORDS];
#define HYPERV_FEAT_EVMCS 12
#define HYPERV_FEAT_IPI 13
#define HYPERV_FEAT_STIMER_DIRECT 14
+#define HYPERV_FEAT_DIRECT_TLBFLUSH 15
#ifndef HYPERV_SPINLOCK_NEVER_RETRY
#define HYPERV_SPINLOCK_NEVER_RETRY 0xFFFFFFFF
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 11b9c854b5..8e999dbcf1 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -1235,6 +1235,27 @@ static int hyperv_handle_properties(CPUState *cs,
r |= 1;
}
+ if (hyperv_feat_enabled(cpu, HYPERV_FEAT_DIRECT_TLBFLUSH)) {
+ if (!kvm_check_extension(cs->kvm_state,
+ KVM_CAP_HYPERV_DIRECT_TLBFLUSH)) {
+ fprintf(stderr,
+ "Kernel doesn't support Hyper-V direct tlbflush.\n");
+ r = -ENOSYS;
+ goto free;
+ }
+
+ if (cpu->expose_kvm ||
+ !hyperv_feat_enabled(cpu, HYPERV_FEAT_TLBFLUSH)) {
+ fprintf(stderr, "Hyper-V direct tlbflush requires Hyper-V %s"
+ " and not expose KVM.\n",
+ kvm_hyperv_properties[HYPERV_FEAT_TLBFLUSH].desc);
+ r = -ENOSYS;
+ goto free;
+ }
+
+ kvm_vcpu_enable_cap(cs, KVM_CAP_HYPERV_DIRECT_TLBFLUSH, 0, 0);
+ }
+
/* Not exposed by KVM but needed to make CPU hotplug in Windows work */
env->features[FEAT_HYPERV_EDX] |= HV_CPU_DYNAMIC_PARTITIONING_AVAILABLE;
--
2.14.5
