i386: Hyper-V Direct TLB flush hypercall

Hyper-V TLFS allows for L0 and L1 hypervisors to collaborate on L2's
TLB flush hypercalls handling. With the correct setup, L2's TLB flush
hypercalls can be handled by L0 directly, without the need to exit to
L1.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220525115949.1294004-6-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/docs/hyperv.txt b/docs/hyperv.txt
index 4b132b1c941a39cf5af00352c263c0eb942e0443..14a7f449ead9048cae062ae31a01decb2cd44fdb 100644 (file)
--- a/docs/hyperv.txt
+++ b/docs/hyperv.txt
@@ -262,6 +262,17 @@ Allow for extended GVA ranges to be passed to Hyper-V TLB flush hypercalls
 
 Requires: hv-tlbflush
 
+3.25. hv-tlbflush-direct
+=========================
+The enlightenment is nested specific, it targets Hyper-V on KVM guests. When
+enabled, it allows L0 (KVM) to directly handle TLB flush hypercalls from L2
+guest without the need to exit to L1 (Hyper-V) hypervisor. While the feature is
+supported for both VMX (Intel) and SVM (AMD), the VMX implementation requires
+Enlightened VMCS ('hv-evmcs') feature to also be enabled.
+
+Requires: hv-vapic
+Recommended: hv-evmcs (Intel)
+
 4. Supplementary features
 =========================
 

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 3429a4e455ab5e684f380dd8d674a381cf4a247d..bb6a5dd49899338a4c3b2317982225e38e8df1c3 100644 (file)
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6974,6 +6974,8 @@ static Property x86_cpu_properties[] = {
                       HYPERV_FEAT_XMM_INPUT, 0),
     DEFINE_PROP_BIT64("hv-tlbflush-ext", X86CPU, hyperv_features,
                       HYPERV_FEAT_TLBFLUSH_EXT, 0),
+    DEFINE_PROP_BIT64("hv-tlbflush-direct", X86CPU, hyperv_features,
+                      HYPERV_FEAT_TLBFLUSH_DIRECT, 0),
     DEFINE_PROP_ON_OFF_AUTO("hv-no-nonarch-coresharing", X86CPU,
                             hyperv_no_nonarch_cs, ON_OFF_AUTO_OFF),
     DEFINE_PROP_BIT64("hv-syndbg", X86CPU, hyperv_features,

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 5ff48257e513f2502fdd62c3909bb00e6652a0a2..82004b65b944132781821248914fc34448fc78de 100644 (file)
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1109,6 +1109,7 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
 #define HYPERV_FEAT_MSR_BITMAP          17
 #define HYPERV_FEAT_XMM_INPUT           18
 #define HYPERV_FEAT_TLBFLUSH_EXT        19
+#define HYPERV_FEAT_TLBFLUSH_DIRECT     20
 
 #ifndef HYPERV_SPINLOCK_NEVER_NOTIFY
 #define HYPERV_SPINLOCK_NEVER_NOTIFY             0xFFFFFFFF

diff --git a/target/i386/kvm/hyperv-proto.h b/target/i386/kvm/hyperv-proto.h
index c7854ed6d306b8a58d303a3dc59d6db169a93809..464fbf09e35ab06bf6a71631444d7083d35b5138 100644 (file)
--- a/target/i386/kvm/hyperv-proto.h
+++ b/target/i386/kvm/hyperv-proto.h
@@ -90,6 +90,7 @@
 /*
  * HV_CPUID_NESTED_FEATURES.EAX bits
  */
+#define HV_NESTED_DIRECT_FLUSH              (1u << 17)
 #define HV_NESTED_MSR_BITMAP                (1u << 19)
 
 /*

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index a11c8e88f6b273bfd1640ab15321b00128c4f91e..f148a6d52fa46a3fb6716b124f40fd18c1fea429 100644 (file)
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -995,6 +995,14 @@ static struct {
         },
         .dependencies = BIT(HYPERV_FEAT_TLBFLUSH)
     },
+    [HYPERV_FEAT_TLBFLUSH_DIRECT] = {
+        .desc = "direct TLB flush (hv-tlbflush-direct)",
+        .flags = {
+            {.func = HV_CPUID_NESTED_FEATURES, .reg = R_EAX,
+             .bits = HV_NESTED_DIRECT_FLUSH}
+        },
+        .dependencies = BIT(HYPERV_FEAT_VAPIC)
+    },
 };
 
 static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max,