2018-02-09 14:18:15

by Wanpeng Li

Subject: [PATCH v2] target-i386: add KVM_HINTS_DEDICATED performance hint

From: Wanpeng Li <[email protected]>

Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
to determine if they run on dedicated vCPUs, allowing optimizations such
as usage of qspinlocks.

Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Eduardo Habkost <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
v1 -> v2:
* add a new feature word

target/i386/cpu.c | 14 ++++++++++++++
target/i386/cpu.h | 3 +++
target/i386/kvm.c | 4 ++++
3 files changed, 21 insertions(+)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index d70954b..e2974ad 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
.cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX,
.tcg_features = TCG_KVM_FEATURES,
},
+ [FEAT_KVM_HINTS] = {
+ .feat_names = {
+ "hint-dedicated", NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
+ },
+ .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
+ .tcg_features = TCG_KVM_FEATURES,
+ },
[FEAT_HYPERV_EAX] = {
.feat_names = {
NULL /* hv_msr_vp_runtime_access */, NULL /* hv_msr_time_refcount_access */,
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index f91e37d..9f73692 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -475,6 +475,7 @@ typedef enum FeatureWord {
FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
FEAT_KVM, /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
+ FEAT_KVM_HINTS, /* CPUID[4000_0001].EDX */
FEAT_HYPERV_EAX, /* CPUID[4000_0003].EAX */
FEAT_HYPERV_EBX, /* CPUID[4000_0003].EBX */
FEAT_HYPERV_EDX, /* CPUID[4000_0003].EDX */
@@ -670,6 +671,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
#define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */
#define CPUID_7_0_EDX_SPEC_CTRL (1U << 26) /* Speculation Control */

+#define KVM_HINTS_DEDICATED (1U << 0)
+
#define CPUID_8000_0008_EBX_IBPB (1U << 12) /* Indirect Branch Prediction Barrier */

#define CPUID_XSAVE_XSAVEOPT (1U << 0)
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index ad4b159..44ee524 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -383,6 +383,9 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
if (!kvm_irqchip_in_kernel()) {
ret &= ~(1U << KVM_FEATURE_PV_UNHALT);
}
+ } else if (function == KVM_CPUID_FEATURES && reg == R_EDX) {
+ ret |= KVM_HINTS_DEDICATED;
+ found = 1;
}

/* fallback for older kernels */
@@ -801,6 +804,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
c = &cpuid_data.entries[cpuid_i++];
c->function = KVM_CPUID_FEATURES | kvm_base;
c->eax = env->features[FEAT_KVM];
+ c->edx = env->features[FEAT_KVM_HINTS];
}

cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
--
2.7.4

2018-02-09 14:34:05

by Eduardo Habkost

Subject: Re: [PATCH v2] target-i386: add KVM_HINTS_DEDICATED performance hint

On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
> to determine if they run on dedicated vCPUs, allowing optimizations such
> as usage of qspinlocks.
>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Radim Krčmář <[email protected]>
> Cc: Eduardo Habkost <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
[...]
> + [FEAT_KVM_HINTS] = {
> + .feat_names = {
> + "hint-dedicated", NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + },
> + .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
> + .tcg_features = TCG_KVM_FEATURES,
> + },

Do you have a pointer to the KVM patch that adds this bit to
Documentation/virtual/kvm/cpuid.txt? I would like to wait until
the KVM CPUID docs are updated before applying the patch to QEMU.

--
Eduardo

2018-03-09 14:18:08

by Eduardo Habkost

Subject: Re: [PATCH v2] target-i386: add KVM_HINTS_DEDICATED performance hint

On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
> to determine if they run on dedicated vCPUs, allowing optimizations such
> as usage of qspinlocks.
>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Radim Krčmář <[email protected]>
> Cc: Eduardo Habkost <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> v1 -> v2:
> * add a new feature word
>
> target/i386/cpu.c | 14 ++++++++++++++
> target/i386/cpu.h | 3 +++
> target/i386/kvm.c | 4 ++++
> 3 files changed, 21 insertions(+)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index d70954b..e2974ad 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX,
> .tcg_features = TCG_KVM_FEATURES,
> },
> + [FEAT_KVM_HINTS] = {
> + .feat_names = {
> + "hint-dedicated", NULL, NULL, NULL,

I suggest naming it "kvm-hint-dedicated", to indicate it's
KVM-specific.

If there are no objections, I can rename it while applying.

With the rename:

Reviewed-by: Eduardo Habkost <[email protected]>


> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + NULL, NULL, NULL, NULL,
> + },
> + .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
> + .tcg_features = TCG_KVM_FEATURES,
> + },
> [FEAT_HYPERV_EAX] = {
> .feat_names = {
> NULL /* hv_msr_vp_runtime_access */, NULL /* hv_msr_time_refcount_access */,
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index f91e37d..9f73692 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -475,6 +475,7 @@ typedef enum FeatureWord {
> FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
> FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
> FEAT_KVM, /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
> + FEAT_KVM_HINTS, /* CPUID[4000_0001].EDX */
> FEAT_HYPERV_EAX, /* CPUID[4000_0003].EAX */
> FEAT_HYPERV_EBX, /* CPUID[4000_0003].EBX */
> FEAT_HYPERV_EDX, /* CPUID[4000_0003].EDX */
> @@ -670,6 +671,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
> #define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */
> #define CPUID_7_0_EDX_SPEC_CTRL (1U << 26) /* Speculation Control */
>
> +#define KVM_HINTS_DEDICATED (1U << 0)
> +
> #define CPUID_8000_0008_EBX_IBPB (1U << 12) /* Indirect Branch Prediction Barrier */
>
> #define CPUID_XSAVE_XSAVEOPT (1U << 0)
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index ad4b159..44ee524 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -383,6 +383,9 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
> if (!kvm_irqchip_in_kernel()) {
> ret &= ~(1U << KVM_FEATURE_PV_UNHALT);
> }
> + } else if (function == KVM_CPUID_FEATURES && reg == R_EDX) {
> + ret |= KVM_HINTS_DEDICATED;
> + found = 1;
> }
>
> /* fallback for older kernels */
> @@ -801,6 +804,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
> c = &cpuid_data.entries[cpuid_i++];
> c->function = KVM_CPUID_FEATURES | kvm_base;
> c->eax = env->features[FEAT_KVM];
> + c->edx = env->features[FEAT_KVM_HINTS];
> }
>
> cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
> --
> 2.7.4
>

--
Eduardo

2018-04-10 09:17:12

by Wanpeng Li

Subject: Re: [PATCH v2] target-i386: add KVM_HINTS_DEDICATED performance hint

Hi Eduardo,
2018-03-09 22:16 GMT+08:00 Eduardo Habkost <[email protected]>:
> On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote:
>> From: Wanpeng Li <[email protected]>
>>
>> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
>> to determine if they run on dedicated vCPUs, allowing optimizations such
>> as usage of qspinlocks.
>>
>> Cc: Paolo Bonzini <[email protected]>
>> Cc: Radim Krčmář <[email protected]>
>> Cc: Eduardo Habkost <[email protected]>
>> Signed-off-by: Wanpeng Li <[email protected]>
>> ---
>> v1 -> v2:
>> * add a new feature word
>>
>> target/i386/cpu.c | 14 ++++++++++++++
>> target/i386/cpu.h | 3 +++
>> target/i386/kvm.c | 4 ++++
>> 3 files changed, 21 insertions(+)
>>
>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>> index d70954b..e2974ad 100644
>> --- a/target/i386/cpu.c
>> +++ b/target/i386/cpu.c
>> @@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX,
>> .tcg_features = TCG_KVM_FEATURES,
>> },
>> + [FEAT_KVM_HINTS] = {
>> + .feat_names = {
>> + "hint-dedicated", NULL, NULL, NULL,
>
> I suggest naming it "kvm-hint-dedicated", to indicate it's
> KVM-specific.

I found this feature is enabled by default w/o kvm-hint-dedicated
parameter, any idea how to make it disabled by default?

Regards,
Wanpeng Li

>
> If there are no objections, I can rename it while applying.
>
> With the rename:
>
> Reviewed-by: Eduardo Habkost <[email protected]>
>
>
>> + NULL, NULL, NULL, NULL,
>> + NULL, NULL, NULL, NULL,
>> + NULL, NULL, NULL, NULL,
>> + NULL, NULL, NULL, NULL,
>> + NULL, NULL, NULL, NULL,
>> + NULL, NULL, NULL, NULL,
>> + NULL, NULL, NULL, NULL,
>> + },
>> + .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
>> + .tcg_features = TCG_KVM_FEATURES,
>> + },
>> [FEAT_HYPERV_EAX] = {
>> .feat_names = {
>> NULL /* hv_msr_vp_runtime_access */, NULL /* hv_msr_time_refcount_access */,
>> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
>> index f91e37d..9f73692 100644
>> --- a/target/i386/cpu.h
>> +++ b/target/i386/cpu.h
>> @@ -475,6 +475,7 @@ typedef enum FeatureWord {
>> FEAT_8000_0008_EBX, /* CPUID[8000_0008].EBX */
>> FEAT_C000_0001_EDX, /* CPUID[C000_0001].EDX */
>> FEAT_KVM, /* CPUID[4000_0001].EAX (KVM_CPUID_FEATURES) */
>> + FEAT_KVM_HINTS, /* CPUID[4000_0001].EDX */
>> FEAT_HYPERV_EAX, /* CPUID[4000_0003].EAX */
>> FEAT_HYPERV_EBX, /* CPUID[4000_0003].EBX */
>> FEAT_HYPERV_EDX, /* CPUID[4000_0003].EDX */
>> @@ -670,6 +671,8 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>> #define CPUID_7_0_EDX_AVX512_4FMAPS (1U << 3) /* AVX512 Multiply Accumulation Single Precision */
>> #define CPUID_7_0_EDX_SPEC_CTRL (1U << 26) /* Speculation Control */
>>
>> +#define KVM_HINTS_DEDICATED (1U << 0)
>> +
>> #define CPUID_8000_0008_EBX_IBPB (1U << 12) /* Indirect Branch Prediction Barrier */
>>
>> #define CPUID_XSAVE_XSAVEOPT (1U << 0)
>> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
>> index ad4b159..44ee524 100644
>> --- a/target/i386/kvm.c
>> +++ b/target/i386/kvm.c
>> @@ -383,6 +383,9 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
>> if (!kvm_irqchip_in_kernel()) {
>> ret &= ~(1U << KVM_FEATURE_PV_UNHALT);
>> }
>> + } else if (function == KVM_CPUID_FEATURES && reg == R_EDX) {
>> + ret |= KVM_HINTS_DEDICATED;
>> + found = 1;
>> }
>>
>> /* fallback for older kernels */
>> @@ -801,6 +804,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
>> c = &cpuid_data.entries[cpuid_i++];
>> c->function = KVM_CPUID_FEATURES | kvm_base;
>> c->eax = env->features[FEAT_KVM];
>> + c->edx = env->features[FEAT_KVM_HINTS];
>> }
>>
>> cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
>> --
>> 2.7.4
>>
>
> --
> Eduardo

2018-04-10 12:01:05

by Eduardo Habkost

Subject: Re: [PATCH v2] target-i386: add KVM_HINTS_DEDICATED performance hint

On Tue, Apr 10, 2018 at 05:13:21PM +0800, Wanpeng Li wrote:
> Hi Eduardo,
> 2018-03-09 22:16 GMT+08:00 Eduardo Habkost <[email protected]>:
> > On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote:
> >> From: Wanpeng Li <[email protected]>
> >>
> >> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
> >> to determine if they run on dedicated vCPUs, allowing optimizations such
> >> as usage of qspinlocks.
> >>
> >> Cc: Paolo Bonzini <[email protected]>
> >> Cc: Radim Krčmář <[email protected]>
> >> Cc: Eduardo Habkost <[email protected]>
> >> Signed-off-by: Wanpeng Li <[email protected]>
> >> ---
> >> v1 -> v2:
> >> * add a new feature word
> >>
> >> target/i386/cpu.c | 14 ++++++++++++++
> >> target/i386/cpu.h | 3 +++
> >> target/i386/kvm.c | 4 ++++
> >> 3 files changed, 21 insertions(+)
> >>
> >> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> >> index d70954b..e2974ad 100644
> >> --- a/target/i386/cpu.c
> >> +++ b/target/i386/cpu.c
> >> @@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> >> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX,
> >> .tcg_features = TCG_KVM_FEATURES,
> >> },
> >> + [FEAT_KVM_HINTS] = {
> >> + .feat_names = {
> >> + "hint-dedicated", NULL, NULL, NULL,
> >
> > I suggest naming it "kvm-hint-dedicated", to indicate it's
> > KVM-specific.
>
> I found this feature is enabled by default w/o kvm-hint-dedicated
> parameter, any idea how to make it disabled by default?

You mean on "-cpu host", right?

The assumption in most of the code is that anything enabled on
GET_SUPPORTED_CPUID should be enabled on "-cpu host". This
shouldn't be the case for FEAT_KVM_HINTS.

Untested fix below.

Signed-off-by: Eduardo Habkost <[email protected]>
---
target/i386/cpu.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 1a6b082b6f..a20fe26573 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -295,6 +295,8 @@ typedef struct FeatureWordInfo {
uint32_t tcg_features; /* Feature flags supported by TCG */
uint32_t unmigratable_flags; /* Feature flags known to be unmigratable */
uint32_t migratable_flags; /* Feature flags known to be migratable */
+ /* Features that shouldn't be auto-enabled by "-cpu host" */
+ uint32_t no_autoenable_flags;
} FeatureWordInfo;

static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
@@ -400,6 +402,11 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
},
.cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
.tcg_features = TCG_KVM_FEATURES,
+ /*
+ * KVM hints aren't auto-enabled by -cpu host, they need to be
+ * explicitly enabled in the command-line.
+ */
+ .no_autoenable_flags = ~0U,
},
[FEAT_HYPERV_EAX] = {
.feat_names = {
@@ -4062,7 +4069,8 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
*/
env->features[w] |=
x86_cpu_get_supported_feature_word(w, cpu->migratable) &
- ~env->user_features[w];
+ ~env->user_features[w] & \
+ ~feature_word_info[w].no_autoenable_flags;
}
}

--
2.14.3

--
Eduardo

2018-04-10 12:07:59

by Paolo Bonzini

Subject: Re: [PATCH v2] target-i386: add KVM_HINTS_DEDICATED performance hint

On 10/04/2018 13:57, Eduardo Habkost wrote:
> On Tue, Apr 10, 2018 at 05:13:21PM +0800, Wanpeng Li wrote:
>> Hi Eduardo,
>> 2018-03-09 22:16 GMT+08:00 Eduardo Habkost <[email protected]>:
>>> On Fri, Feb 09, 2018 at 06:15:25AM -0800, Wanpeng Li wrote:
>>>> From: Wanpeng Li <[email protected]>
>>>>
>>>> Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
>>>> to determine if they run on dedicated vCPUs, allowing optimizations such
>>>> as usage of qspinlocks.
>>>>
>>>> Cc: Paolo Bonzini <[email protected]>
>>>> Cc: Radim Krčmář <[email protected]>
>>>> Cc: Eduardo Habkost <[email protected]>
>>>> Signed-off-by: Wanpeng Li <[email protected]>
>>>> ---
>>>> v1 -> v2:
>>>> * add a new feature word
>>>>
>>>> target/i386/cpu.c | 14 ++++++++++++++
>>>> target/i386/cpu.h | 3 +++
>>>> target/i386/kvm.c | 4 ++++
>>>> 3 files changed, 21 insertions(+)
>>>>
>>>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>>>> index d70954b..e2974ad 100644
>>>> --- a/target/i386/cpu.c
>>>> +++ b/target/i386/cpu.c
>>>> @@ -358,6 +358,20 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>>>> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EAX,
>>>> .tcg_features = TCG_KVM_FEATURES,
>>>> },
>>>> + [FEAT_KVM_HINTS] = {
>>>> + .feat_names = {
>>>> + "hint-dedicated", NULL, NULL, NULL,
>>>
>>> I suggest naming it "kvm-hint-dedicated", to indicate it's
>>> KVM-specific.
>>
>> I found this feature is enabled by default w/o kvm-hint-dedicated
>> parameter, any idea how to make it disabled by default?
>
> You mean on "-cpu host", right?
>
> The assumption in most of the code is that anything enabled on
> GET_SUPPORTED_CPUID should be enabled on "-cpu host". This
> shouldn't be the case for FEAT_KVM_HINTS.
>
> Untested fix below.
>
> Signed-off-by: Eduardo Habkost <[email protected]>
> ---
> target/i386/cpu.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 1a6b082b6f..a20fe26573 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -295,6 +295,8 @@ typedef struct FeatureWordInfo {
> uint32_t tcg_features; /* Feature flags supported by TCG */
> uint32_t unmigratable_flags; /* Feature flags known to be unmigratable */
> uint32_t migratable_flags; /* Feature flags known to be migratable */
> + /* Features that shouldn't be auto-enabled by "-cpu host" */
> + uint32_t no_autoenable_flags;
> } FeatureWordInfo;
>
> static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> @@ -400,6 +402,11 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> },
> .cpuid_eax = KVM_CPUID_FEATURES, .cpuid_reg = R_EDX,
> .tcg_features = TCG_KVM_FEATURES,
> + /*
> + * KVM hints aren't auto-enabled by -cpu host, they need to be
> + * explicitly enabled in the command-line.
> + */
> + .no_autoenable_flags = ~0U,
> },
> [FEAT_HYPERV_EAX] = {
> .feat_names = {
> @@ -4062,7 +4069,8 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
> */
> env->features[w] |=
> x86_cpu_get_supported_feature_word(w, cpu->migratable) &
> - ~env->user_features[w];
> + ~env->user_features[w] & \
> + ~feature_word_info[w].no_autoenable_flags;
> }
> }
>
>

Reviewed-by: Paolo Bonzini <[email protected]>