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i386/kvm: implement 'hv-passthrough' mode 

In many case we just want to give Windows guests all currently supported
Hyper-V enlightenments and that's where this new mode may come handy. We
pass through what was returned by KVM_GET_SUPPORTED_HV_CPUID.

hv_cpuid_check_and_set() is modified to also set cpu->hyperv_* flags as
we may want to check them later (and we actually do for hv_runtime,
hv_synic,...).

'hv-passthrough' is a development only feature, a migration blocker is
added to prevent issues while migrating between hosts with different
feature sets.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20190517141924.19024-6-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2019-05-17 16:19:20 +02:00 committed by Paolo Bonzini
parent fb19f72b77
commit e48ddcc6ce
4 changed files with 87 additions and 14 deletions
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10
docs/hyperv.txt
View File

@ -175,6 +175,16 @@ without the feature to find out if enabling it is beneficial.
Requires: hv-vapic
4. Development features
========================
In some cases (e.g. during development) it may make sense to use QEMU in
'pass-through' mode and give Windows guests all enlightenments currently
supported by KVM. This pass-through mode is enabled by "hv-passthrough" CPU
flag.
Note: enabling this flag effectively prevents migration as supported features
may differ between target and destination.
4. Useful links
================
Hyper-V Top Level Functional specification and other information:

1
target/i386/cpu.c
View File

@ -5883,6 +5883,7 @@ static Property x86_cpu_properties[] = {
HYPERV_FEAT_EVMCS, 0),
DEFINE_PROP_BIT64("hv-ipi", X86CPU, hyperv_features,
HYPERV_FEAT_IPI, 0),
DEFINE_PROP_BOOL("hv-passthrough", X86CPU, hyperv_passthrough, false),
DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true),
DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),

1
target/i386/cpu.h
View File

@ -1390,6 +1390,7 @@ struct X86CPU {
char *hyperv_vendor_id;
bool hyperv_synic_kvm_only;
uint64_t hyperv_features;
bool hyperv_passthrough;
bool check_cpuid;
bool enforce_cpuid;

89
target/i386/kvm.c
View File

@ -639,7 +639,7 @@ static bool hyperv_enabled(X86CPU *cpu)
CPUState *cs = CPU(cpu);
return kvm_check_extension(cs->kvm_state, KVM_CAP_HYPERV) > 0 &&
((cpu->hyperv_spinlock_attempts != HYPERV_SPINLOCK_NEVER_RETRY) ||
cpu->hyperv_features);
cpu->hyperv_features || cpu->hyperv_passthrough);
}
static int kvm_arch_set_tsc_khz(CPUState *cs)
@ -985,10 +985,10 @@ static int hv_cpuid_check_and_set(CPUState *cs, struct kvm_cpuid2 *cpuid,
{
X86CPU *cpu = X86_CPU(cs);
CPUX86State *env = &cpu->env;
uint32_t r, fw, bits;;
uint32_t r, fw, bits;
int i;
if (!hyperv_feat_enabled(cpu, feature)) {
if (!hyperv_feat_enabled(cpu, feature) && !cpu->hyperv_passthrough) {
return 0;
}
@ -1001,15 +1001,23 @@ static int hv_cpuid_check_and_set(CPUState *cs, struct kvm_cpuid2 *cpuid,
}
if (hv_cpuid_get_fw(cpuid, fw, &r) || (r & bits) != bits) {
fprintf(stderr,
"Hyper-V %s is not supported by kernel\n",
kvm_hyperv_properties[feature].desc);
return 1;
if (hyperv_feat_enabled(cpu, feature)) {
fprintf(stderr,
"Hyper-V %s is not supported by kernel\n",
kvm_hyperv_properties[feature].desc);
return 1;
} else {
return 0;
}
}
env->features[fw] |= bits;
}
if (cpu->hyperv_passthrough) {
cpu->hyperv_features |= BIT(feature);
}
return 0;
}
@ -1027,22 +1035,29 @@ static int hyperv_handle_properties(CPUState *cs,
struct kvm_cpuid_entry2 *c;
uint32_t signature[3];
uint32_t cpuid_i = 0;
int r = 0;
int r;
if (!hyperv_enabled(cpu))
return 0;
if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS)) {
if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) ||
cpu->hyperv_passthrough) {
uint16_t evmcs_version;
if (kvm_vcpu_enable_cap(cs, KVM_CAP_HYPERV_ENLIGHTENED_VMCS, 0,
(uintptr_t)&evmcs_version)) {
r = kvm_vcpu_enable_cap(cs, KVM_CAP_HYPERV_ENLIGHTENED_VMCS, 0,
(uintptr_t)&evmcs_version);
if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) && r) {
fprintf(stderr, "Hyper-V %s is not supported by kernel\n",
kvm_hyperv_properties[HYPERV_FEAT_EVMCS].desc);
return -ENOSYS;
}
env->features[FEAT_HV_RECOMM_EAX] |= HV_ENLIGHTENED_VMCS_RECOMMENDED;
env->features[FEAT_HV_NESTED_EAX] = evmcs_version;
if (!r) {
env->features[FEAT_HV_RECOMM_EAX] |=
HV_ENLIGHTENED_VMCS_RECOMMENDED;
env->features[FEAT_HV_NESTED_EAX] = evmcs_version;
}
}
if (kvm_check_extension(cs->kvm_state, KVM_CAP_HYPERV_CPUID) > 0) {
@ -1051,8 +1066,33 @@ static int hyperv_handle_properties(CPUState *cs,
cpuid = get_supported_hv_cpuid_legacy(cs);
}
if (cpu->hyperv_passthrough) {
memcpy(cpuid_ent, &cpuid->entries[0],
cpuid->nent * sizeof(cpuid->entries[0]));
c = cpuid_find_entry(cpuid, HV_CPUID_FEATURES, 0);
if (c) {
env->features[FEAT_HYPERV_EAX] = c->eax;
env->features[FEAT_HYPERV_EBX] = c->ebx;
env->features[FEAT_HYPERV_EDX] = c->eax;
}
c = cpuid_find_entry(cpuid, HV_CPUID_ENLIGHTMENT_INFO, 0);
if (c) {
env->features[FEAT_HV_RECOMM_EAX] = c->eax;
/* hv-spinlocks may have been overriden */
if (cpu->hyperv_spinlock_attempts != HYPERV_SPINLOCK_NEVER_RETRY) {
c->ebx = cpu->hyperv_spinlock_attempts;
}
}
c = cpuid_find_entry(cpuid, HV_CPUID_NESTED_FEATURES, 0);
if (c) {
env->features[FEAT_HV_NESTED_EAX] = c->eax;
}
}
/* Features */
r |= hv_cpuid_check_and_set(cs, cpuid, HYPERV_FEAT_RELAXED);
r = hv_cpuid_check_and_set(cs, cpuid, HYPERV_FEAT_RELAXED);
r |= hv_cpuid_check_and_set(cs, cpuid, HYPERV_FEAT_VAPIC);
r |= hv_cpuid_check_and_set(cs, cpuid, HYPERV_FEAT_TIME);
r |= hv_cpuid_check_and_set(cs, cpuid, HYPERV_FEAT_CRASH);
@ -1085,6 +1125,12 @@ static int hyperv_handle_properties(CPUState *cs,
goto free;
}
if (cpu->hyperv_passthrough) {
/* We already copied all feature words from KVM as is */
r = cpuid->nent;
goto free;
}
c = &cpuid_ent[cpuid_i++];
c->function = HV_CPUID_VENDOR_AND_MAX_FUNCTIONS;
if (!cpu->hyperv_vendor_id) {
@ -1156,11 +1202,26 @@ free:
return r;
}
static Error *hv_passthrough_mig_blocker;
static int hyperv_init_vcpu(X86CPU *cpu)
{
CPUState *cs = CPU(cpu);
Error *local_err = NULL;
int ret;
if (cpu->hyperv_passthrough && hv_passthrough_mig_blocker == NULL) {
error_setg(&hv_passthrough_mig_blocker,
"'hv-passthrough' CPU flag prevents migration, use explicit"
" set of hv-* flags instead");
ret = migrate_add_blocker(hv_passthrough_mig_blocker, &local_err);
if (local_err) {
error_report_err(local_err);
error_free(hv_passthrough_mig_blocker);
return ret;
}
}
if (hyperv_feat_enabled(cpu, HYPERV_FEAT_VPINDEX) && !hv_vpindex_settable) {
/*
* the kernel doesn't support setting vp_index; assert that its value