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i386: Hyper-V Enlightened MSR bitmap feature

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The newly introduced enlightenment allow L0 (KVM) and L1 (Hyper-V)
hypervisors to collaborate to avoid unnecessary updates to L2
MSR-Bitmap upon vmexits.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20220525115949.1294004-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2022-05-25 13:59:45 +02:00 committed by Paolo Bonzini
parent 7110fe56c1
commit 869840d26c
5 changed files with 24 additions and 0 deletions
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9
docs/hyperv.txt
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@ -239,6 +239,15 @@ This enlightenment requires a VMBus device (-device vmbus-bridge,irq=15)
and the follow enlightenments to work:
hv-relaxed,hv_time,hv-vapic,hv-vpindex,hv-synic,hv-runtime,hv-stimer
3.22. hv-emsr-bitmap
=====================
The enlightenment is nested specific, it targets Hyper-V on KVM guests. When
enabled, it allows L0 (KVM) and L1 (Hyper-V) hypervisors to collaborate to
avoid unnecessary updates to L2 MSR-Bitmap upon vmexits. While the protocol is
supported for both VMX (Intel) and SVM (AMD), the VMX implementation requires
Enlightened VMCS ('hv-evmcs') feature to also be enabled.
Recommended: hv-evmcs (Intel)
4. Supplementary features
=========================

2
target/i386/cpu.c
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@ -6968,6 +6968,8 @@ static Property x86_cpu_properties[] = {
HYPERV_FEAT_STIMER_DIRECT, 0),
DEFINE_PROP_BIT64("hv-avic", X86CPU, hyperv_features,
HYPERV_FEAT_AVIC, 0),
DEFINE_PROP_BIT64("hv-emsr-bitmap", X86CPU, hyperv_features,
HYPERV_FEAT_MSR_BITMAP, 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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@ -1106,6 +1106,7 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
#define HYPERV_FEAT_STIMER_DIRECT 14
#define HYPERV_FEAT_AVIC 15
#define HYPERV_FEAT_SYNDBG 16
#define HYPERV_FEAT_MSR_BITMAP 17
#ifndef HYPERV_SPINLOCK_NEVER_NOTIFY
#define HYPERV_SPINLOCK_NEVER_NOTIFY 0xFFFFFFFF

5
target/i386/kvm/hyperv-proto.h
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@ -86,6 +86,11 @@
*/
#define HV_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING (1u << 1)
/*
* HV_CPUID_NESTED_FEATURES.EAX bits
*/
#define HV_NESTED_MSR_BITMAP (1u << 19)
/*
* Basic virtualized MSRs
*/

7
target/i386/kvm/kvm.c
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@ -973,6 +973,13 @@ static struct {
.dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED)
},
#endif
[HYPERV_FEAT_MSR_BITMAP] = {
.desc = "enlightened MSR-Bitmap (hv-emsr-bitmap)",
.flags = {
{.func = HV_CPUID_NESTED_FEATURES, .reg = R_EAX,
.bits = HV_NESTED_MSR_BITMAP}
}
},
};
static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max,