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Re: [PATCH 5/5] i386: provide simple 'hyperv=on' option to x86 machine t
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From: |
Vitaly Kuznetsov |
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Subject: |
Re: [PATCH 5/5] i386: provide simple 'hyperv=on' option to x86 machine types |
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Date: |
Thu, 17 Dec 2020 10:34:17 +0100 |
Eduardo Habkost <ehabkost@redhat.com> writes:
> On Thu, Nov 19, 2020 at 11:32:21AM +0100, Vitaly Kuznetsov wrote:
>> Enabling Hyper-V emulation for a Windows VM is a tiring experience as it
>> requires listing all currently supported enlightenments ("hv_*" CPU
>> features) explicitly. We do have a 'hv_passthrough' mode enabling
>> everything but it can't be used in production as it prevents migration.
>>
>> Introduce a simple 'hyperv=on' option for all x86 machine types enabling
>> all currently supported Hyper-V enlightenments. Later, when new
>> enlightenments get implemented, we will be adding them to newer machine
>> types only (by disabling them for legacy machine types) thus preserving
>> migration.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
> [...]
>> ---
>> docs/hyperv.txt | 8 ++++++++
>> hw/i386/x86.c | 30 ++++++++++++++++++++++++++++++
>> include/hw/i386/x86.h | 7 +++++++
>> target/i386/cpu.c | 14 ++++++++++++++
>> 4 files changed, 59 insertions(+)
>>
>> diff --git a/docs/hyperv.txt b/docs/hyperv.txt
>> index 5df00da54fc4..1a76a07f8417 100644
>> --- a/docs/hyperv.txt
>> +++ b/docs/hyperv.txt
>> @@ -29,6 +29,14 @@ When any set of the Hyper-V enlightenments is enabled,
>> QEMU changes hypervisor
>> identification (CPUID 0x40000000..0x4000000A) to Hyper-V. KVM identification
>> and features are kept in leaves 0x40000100..0x40000101.
>>
>> +Hyper-V enlightenments can be enabled in bulk by specifying 'hyperv=on' to
>> an
>> +x86 machine type:
>> +
>> + qemu-system-x86_64 -machine q35,accel=kvm,kernel-irqchip=split,hyperv=on
>> ...
>> +
>> +Note, new enlightenments are only added to the latest (in-develompent)
>> machine
>> +type, older machine types keep the list of the supported features intact to
>> +safeguard migration.
>>
>> 3. Existing enlightenments
>> ===========================
>> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
>> index 5944fc44edca..57f27d56ecc6 100644
>> --- a/hw/i386/x86.c
>> +++ b/hw/i386/x86.c
>> @@ -1171,6 +1171,20 @@ static void x86_machine_set_acpi(Object *obj, Visitor
>> *v, const char *name,
>> visit_type_OnOffAuto(v, name, &x86ms->acpi, errp);
>> }
>>
>> +static bool x86_machine_get_hyperv(Object *obj, Error **errp)
>> +{
>> + X86MachineState *x86ms = X86_MACHINE(obj);
>> +
>> + return x86ms->hyperv_enabled;
>> +}
>> +
>> +static void x86_machine_set_hyperv(Object *obj, bool value, Error **errp)
>> +{
>> + X86MachineState *x86ms = X86_MACHINE(obj);
>> +
>> + x86ms->hyperv_enabled = value;
>> +}
>> +
>> static void x86_machine_initfn(Object *obj)
>> {
>> X86MachineState *x86ms = X86_MACHINE(obj);
>> @@ -1194,6 +1208,16 @@ static void x86_machine_class_init(ObjectClass *oc,
>> void *data)
>> x86mc->save_tsc_khz = true;
>> nc->nmi_monitor_handler = x86_nmi;
>>
>> + /* Hyper-V features enabled with 'hyperv=on' */
>> + x86mc->default_hyperv_features = BIT(HYPERV_FEAT_RELAXED) |
>> + BIT(HYPERV_FEAT_VAPIC) | BIT(HYPERV_FEAT_TIME) |
>> + BIT(HYPERV_FEAT_CRASH) | BIT(HYPERV_FEAT_RESET) |
>> + BIT(HYPERV_FEAT_VPINDEX) | BIT(HYPERV_FEAT_RUNTIME) |
>> + BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_STIMER) |
>> + BIT(HYPERV_FEAT_FREQUENCIES) | BIT(HYPERV_FEAT_REENLIGHTENMENT) |
>> + BIT(HYPERV_FEAT_TLBFLUSH) | BIT(HYPERV_FEAT_EVMCS) |
>> + BIT(HYPERV_FEAT_IPI) | BIT(HYPERV_FEAT_STIMER_DIRECT);
>> +
>> object_class_property_add(oc, X86_MACHINE_SMM, "OnOffAuto",
>> x86_machine_get_smm, x86_machine_set_smm,
>> NULL, NULL);
>> @@ -1205,6 +1229,12 @@ static void x86_machine_class_init(ObjectClass *oc,
>> void *data)
>> NULL, NULL);
>> object_class_property_set_description(oc, X86_MACHINE_ACPI,
>> "Enable ACPI");
>> +
>> + object_class_property_add_bool(oc, X86_MACHINE_HYPERV,
>> + x86_machine_get_hyperv, x86_machine_set_hyperv);
>> +
>> + object_class_property_set_description(oc, X86_MACHINE_HYPERV,
>> + "Enable Hyper-V enlightenments");
>> }
>>
>> static const TypeInfo x86_machine_info = {
>> diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h
>> index 739fac50871b..598abd1be806 100644
>> --- a/include/hw/i386/x86.h
>> +++ b/include/hw/i386/x86.h
>> @@ -38,6 +38,9 @@ struct X86MachineClass {
>> bool save_tsc_khz;
>> /* Enables contiguous-apic-ID mode */
>> bool compat_apic_id_mode;
>> +
>> + /* Hyper-V features enabled with 'hyperv=on' */
>> + uint64_t default_hyperv_features;
>> };
>>
>> struct X86MachineState {
>> @@ -71,10 +74,14 @@ struct X86MachineState {
>> * will be translated to MSI messages in the address space.
>> */
>> AddressSpace *ioapic_as;
>> +
>> + /* Hyper-V emulation */
>> + bool hyperv_enabled;
>> };
>>
>> #define X86_MACHINE_SMM "smm"
>> #define X86_MACHINE_ACPI "acpi"
>> +#define X86_MACHINE_HYPERV "hyperv"
>>
>> #define TYPE_X86_MACHINE MACHINE_TYPE_NAME("x86")
>> OBJECT_DECLARE_TYPE(X86MachineState, X86MachineClass, X86_MACHINE)
>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>> index 83aca942d87c..63a931679d73 100644
>> --- a/target/i386/cpu.c
>> +++ b/target/i386/cpu.c
>> @@ -53,6 +53,7 @@
>> #include "sysemu/tcg.h"
>> #include "hw/qdev-properties.h"
>> #include "hw/i386/topology.h"
>> +#include "hw/i386/x86.h"
>> #ifndef CONFIG_USER_ONLY
>> #include "exec/address-spaces.h"
>> #include "hw/i386/apic_internal.h"
>> @@ -6511,8 +6512,21 @@ static void x86_cpu_filter_features(X86CPU *cpu, bool
>> verbose)
>>
>> static void x86_cpu_hyperv_realize(X86CPU *cpu)
>> {
>> + X86MachineState *x86ms = X86_MACHINE(qdev_get_machine());
>> + X86MachineClass *x86mc = X86_MACHINE_GET_CLASS(x86ms);
>> + uint64_t feat;
>> size_t len;
>>
>> + if (x86ms->hyperv_enabled) {
>> + feat = x86mc->default_hyperv_features;
>> + /* Enlightened VMCS is only available on Intel/VMX */
>> + if (!cpu_has_vmx(&cpu->env)) {
>> + feat &= ~BIT(HYPERV_FEAT_EVMCS);
>> + }
>> +
>> + cpu->hyperv_features |= feat;
>> + }
>
> I had to dequeue this because it doesn't compile with
> CONFIG_USER_ONLY:
>
> https://gitlab.com/ehabkost/qemu/-/jobs/916651017
>
> The easiest solution would be to wrap the new code in #ifndef
> CONFIG_USER_ONLY, but maybe we should try to move all
> X86Machine-specific code from cpu.c to
> hw/i386/x86.c:x86_cpu_pre_plug().
Bummer,
let me try the suggestion.
--
Vitaly