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i386: Hyper-V Direct TLB flush hypercall

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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>
This commit is contained in:
Vitaly Kuznetsov 2022-05-25 13:59:48 +02:00 committed by Paolo Bonzini
parent aa6bb5fad5
commit 3aae0854b2
5 changed files with 23 additions and 0 deletions
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11
docs/hyperv.txt
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@ -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
=========================

2
target/i386/cpu.c
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@ -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,

1
target/i386/cpu.h
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@ -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

1
target/i386/kvm/hyperv-proto.h
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@ -90,6 +90,7 @@
/*
* HV_CPUID_NESTED_FEATURES.EAX bits
*/
#define HV_NESTED_DIRECT_FLUSH (1u << 17)
#define HV_NESTED_MSR_BITMAP (1u << 19)
/*

8
target/i386/kvm/kvm.c
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@ -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,