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[PATCH v6 15/19] i386: expand Hyper-V features during CPU feature expansion time

Vitaly Kuznetsov posted 19 patches 4 years, 9 months ago
There is a newer version of this series
[PATCH v6 15/19] i386: expand Hyper-V features during CPU feature expansion time
Posted by Vitaly Kuznetsov 4 years, 9 months ago 
To make Hyper-V features appear in e.g. QMP query-cpu-model-expansion we
need to expand and set the corresponding CPUID leaves early. Modify
x86_cpu_get_supported_feature_word() to call newly intoduced Hyper-V
specific kvm_hv_get_supported_cpuid() instead of
kvm_arch_get_supported_cpuid(). We can't use kvm_arch_get_supported_cpuid()
as Hyper-V specific CPUID leaves intersect with KVM's.

Note, early expansion will only happen when KVM supports system wide
KVM_GET_SUPPORTED_HV_CPUID ioctl (KVM_CAP_SYS_HYPERV_CPUID).

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 target/i386/cpu.c          |  4 ++++
 target/i386/kvm/kvm-stub.c |  5 +++++
 target/i386/kvm/kvm.c      | 15 ++++++++++++---
 target/i386/kvm/kvm_i386.h |  1 +
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index d72b8760e7a3..18b57f3d8b9c 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6514,6 +6514,10 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
     if (env->cpuid_xlevel2 == UINT32_MAX) {
         env->cpuid_xlevel2 = env->cpuid_min_xlevel2;
     }
+
+    if (kvm_enabled()) {
+        kvm_hyperv_expand_features(cpu, errp);
+    }
 }
 
 /*
diff --git a/target/i386/kvm/kvm-stub.c b/target/i386/kvm/kvm-stub.c
index 92f49121b8fa..7f175faa3abd 100644
--- a/target/i386/kvm/kvm-stub.c
+++ b/target/i386/kvm/kvm-stub.c
@@ -39,3 +39,8 @@ bool kvm_hv_vpindex_settable(void)
 {
     return false;
 }
+
+void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
+{
+    return;
+}
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index a42263b24fca..d5551c4ab5cf 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1216,13 +1216,22 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
  * of 'hv_passthrough' mode and fills the environment with all supported
  * Hyper-V features.
  */
-static void hyperv_expand_features(CPUState *cs, Error **errp)
+void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
 {
-    X86CPU *cpu = X86_CPU(cs);
+    CPUState *cs = CPU(cpu);
 
     if (!hyperv_enabled(cpu))
         return;
 
+    /*
+     * When kvm_hyperv_expand_features is called at CPU feature expansion
+     * time per-CPU kvm_state is not available yet so we can only proceed
+     * when KVM_CAP_SYS_HYPERV_CPUID is supported.
+     */
+    if (!cs->kvm_state &&
+        !kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID))
+        return;
+
     if (cpu->hyperv_passthrough) {
         cpu->hyperv_vendor_id[0] =
             hv_cpuid_get_host(cs, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, R_EBX);
@@ -1556,7 +1565,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
     env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
 
     /* Paravirtualization CPUIDs */
-    hyperv_expand_features(cs, &local_err);
+    kvm_hyperv_expand_features(cpu, &local_err);
     if (local_err) {
         error_report_err(local_err);
         return -ENOSYS;
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index dc725083891c..f1176491051d 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -47,6 +47,7 @@ bool kvm_has_x2apic_api(void);
 bool kvm_has_waitpkg(void);
 
 bool kvm_hv_vpindex_settable(void);
+void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
 
 uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address);
 
-- 
2.30.2
Re: [PATCH v6 15/19] i386: expand Hyper-V features during CPU feature expansion time
Posted by Eduardo Habkost 4 years, 8 months ago 
On Thu, Apr 22, 2021 at 06:11:26PM +0200, Vitaly Kuznetsov wrote:
> To make Hyper-V features appear in e.g. QMP query-cpu-model-expansion we
> need to expand and set the corresponding CPUID leaves early. Modify
> x86_cpu_get_supported_feature_word() to call newly intoduced Hyper-V
> specific kvm_hv_get_supported_cpuid() instead of
> kvm_arch_get_supported_cpuid(). We can't use kvm_arch_get_supported_cpuid()
> as Hyper-V specific CPUID leaves intersect with KVM's.
> 
> Note, early expansion will only happen when KVM supports system wide
> KVM_GET_SUPPORTED_HV_CPUID ioctl (KVM_CAP_SYS_HYPERV_CPUID).
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  target/i386/cpu.c          |  4 ++++
>  target/i386/kvm/kvm-stub.c |  5 +++++
>  target/i386/kvm/kvm.c      | 15 ++++++++++++---
>  target/i386/kvm/kvm_i386.h |  1 +
>  4 files changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index d72b8760e7a3..18b57f3d8b9c 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -6514,6 +6514,10 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
>      if (env->cpuid_xlevel2 == UINT32_MAX) {
>          env->cpuid_xlevel2 = env->cpuid_min_xlevel2;
>      }
> +
> +    if (kvm_enabled()) {
> +        kvm_hyperv_expand_features(cpu, errp);
> +    }
>  }
>  
>  /*
> diff --git a/target/i386/kvm/kvm-stub.c b/target/i386/kvm/kvm-stub.c
> index 92f49121b8fa..7f175faa3abd 100644
> --- a/target/i386/kvm/kvm-stub.c
> +++ b/target/i386/kvm/kvm-stub.c
> @@ -39,3 +39,8 @@ bool kvm_hv_vpindex_settable(void)
>  {
>      return false;
>  }
> +
> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
> +{
> +    return;

Maybe we should make it abort()?  This function should never be
called if KVM is disabled.

> +}
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index a42263b24fca..d5551c4ab5cf 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -1216,13 +1216,22 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
>   * of 'hv_passthrough' mode and fills the environment with all supported
>   * Hyper-V features.
>   */
> -static void hyperv_expand_features(CPUState *cs, Error **errp)
> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
>  {
> -    X86CPU *cpu = X86_CPU(cs);
> +    CPUState *cs = CPU(cpu);
>  
>      if (!hyperv_enabled(cpu))
>          return;
>  
> +    /*
> +     * When kvm_hyperv_expand_features is called at CPU feature expansion
> +     * time per-CPU kvm_state is not available yet so we can only proceed
> +     * when KVM_CAP_SYS_HYPERV_CPUID is supported.
> +     */
> +    if (!cs->kvm_state &&
> +        !kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID))
> +        return;
> +
>      if (cpu->hyperv_passthrough) {
>          cpu->hyperv_vendor_id[0] =
>              hv_cpuid_get_host(cs, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, R_EBX);
> @@ -1556,7 +1565,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
>      env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
>  
>      /* Paravirtualization CPUIDs */
> -    hyperv_expand_features(cs, &local_err);
> +    kvm_hyperv_expand_features(cpu, &local_err);

Do we still need to call the function again here?

If the first expansion isn't expanding everything, I'm afraid
this second call will hide bugs in query-cpu-model-expansion.


>      if (local_err) {
>          error_report_err(local_err);
>          return -ENOSYS;
> diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
> index dc725083891c..f1176491051d 100644
> --- a/target/i386/kvm/kvm_i386.h
> +++ b/target/i386/kvm/kvm_i386.h
> @@ -47,6 +47,7 @@ bool kvm_has_x2apic_api(void);
>  bool kvm_has_waitpkg(void);
>  
>  bool kvm_hv_vpindex_settable(void);
> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
>  
>  uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address);
>  
> -- 
> 2.30.2
> 

-- 
Eduardo
Re: [PATCH v6 15/19] i386: expand Hyper-V features during CPU feature expansion time
Posted by Vitaly Kuznetsov 4 years, 8 months ago 
Eduardo Habkost <ehabkost@redhat.com> writes:

> On Thu, Apr 22, 2021 at 06:11:26PM +0200, Vitaly Kuznetsov wrote:
>> To make Hyper-V features appear in e.g. QMP query-cpu-model-expansion we
>> need to expand and set the corresponding CPUID leaves early. Modify
>> x86_cpu_get_supported_feature_word() to call newly intoduced Hyper-V
>> specific kvm_hv_get_supported_cpuid() instead of
>> kvm_arch_get_supported_cpuid(). We can't use kvm_arch_get_supported_cpuid()
>> as Hyper-V specific CPUID leaves intersect with KVM's.
>> 
>> Note, early expansion will only happen when KVM supports system wide
>> KVM_GET_SUPPORTED_HV_CPUID ioctl (KVM_CAP_SYS_HYPERV_CPUID).
>> 
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>>  target/i386/cpu.c          |  4 ++++
>>  target/i386/kvm/kvm-stub.c |  5 +++++
>>  target/i386/kvm/kvm.c      | 15 ++++++++++++---
>>  target/i386/kvm/kvm_i386.h |  1 +
>>  4 files changed, 22 insertions(+), 3 deletions(-)
>> 
>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>> index d72b8760e7a3..18b57f3d8b9c 100644
>> --- a/target/i386/cpu.c
>> +++ b/target/i386/cpu.c
>> @@ -6514,6 +6514,10 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
>>      if (env->cpuid_xlevel2 == UINT32_MAX) {
>>          env->cpuid_xlevel2 = env->cpuid_min_xlevel2;
>>      }
>> +
>> +    if (kvm_enabled()) {
>> +        kvm_hyperv_expand_features(cpu, errp);
>> +    }
>>  }
>>  
>>  /*
>> diff --git a/target/i386/kvm/kvm-stub.c b/target/i386/kvm/kvm-stub.c
>> index 92f49121b8fa..7f175faa3abd 100644
>> --- a/target/i386/kvm/kvm-stub.c
>> +++ b/target/i386/kvm/kvm-stub.c
>> @@ -39,3 +39,8 @@ bool kvm_hv_vpindex_settable(void)
>>  {
>>      return false;
>>  }
>> +
>> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
>> +{
>> +    return;
>
> Maybe we should make it abort()?  This function should never be
> called if KVM is disabled.
>

Sure, can do that.

>> +}
>> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
>> index a42263b24fca..d5551c4ab5cf 100644
>> --- a/target/i386/kvm/kvm.c
>> +++ b/target/i386/kvm/kvm.c
>> @@ -1216,13 +1216,22 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
>>   * of 'hv_passthrough' mode and fills the environment with all supported
>>   * Hyper-V features.
>>   */
>> -static void hyperv_expand_features(CPUState *cs, Error **errp)
>> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
>>  {
>> -    X86CPU *cpu = X86_CPU(cs);
>> +    CPUState *cs = CPU(cpu);
>>  
>>      if (!hyperv_enabled(cpu))
>>          return;
>>  
>> +    /*
>> +     * When kvm_hyperv_expand_features is called at CPU feature expansion
>> +     * time per-CPU kvm_state is not available yet so we can only proceed
>> +     * when KVM_CAP_SYS_HYPERV_CPUID is supported.
>> +     */
>> +    if (!cs->kvm_state &&
>> +        !kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID))
>> +        return;
>> +
>>      if (cpu->hyperv_passthrough) {
>>          cpu->hyperv_vendor_id[0] =
>>              hv_cpuid_get_host(cs, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, R_EBX);
>> @@ -1556,7 +1565,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
>>      env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
>>  
>>      /* Paravirtualization CPUIDs */
>> -    hyperv_expand_features(cs, &local_err);
>> +    kvm_hyperv_expand_features(cpu, &local_err);
>
> Do we still need to call the function again here?
>
> If the first expansion isn't expanding everything, I'm afraid
> this second call will hide bugs in query-cpu-model-expansion.
>

The first expansion will do nothing if KVM_CAP_SYS_HYPERV_CPUID is not
supported, calling it here allows us to proceed. The series makes
'query-cpu-model-expansion' output correct only with
KVM_CAP_SYS_HYPERV_CPUID, without it we don't seem to be able to do much
(unless we decide to create a 'scratch' CPU or something like that).

>
>>      if (local_err) {
>>          error_report_err(local_err);
>>          return -ENOSYS;
>> diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
>> index dc725083891c..f1176491051d 100644
>> --- a/target/i386/kvm/kvm_i386.h
>> +++ b/target/i386/kvm/kvm_i386.h
>> @@ -47,6 +47,7 @@ bool kvm_has_x2apic_api(void);
>>  bool kvm_has_waitpkg(void);
>>  
>>  bool kvm_hv_vpindex_settable(void);
>> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
>>  
>>  uint64_t kvm_swizzle_msi_ext_dest_id(uint64_t address);
>>  
>> -- 
>> 2.30.2
>> 

-- 
Vitaly
Re: [PATCH v6 15/19] i386: expand Hyper-V features during CPU feature expansion time
Posted by Eduardo Habkost 4 years, 8 months ago 
On Mon, May 24, 2021 at 02:13:09PM +0200, Vitaly Kuznetsov wrote:
[...]
> >> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> >> index a42263b24fca..d5551c4ab5cf 100644
> >> --- a/target/i386/kvm/kvm.c
> >> +++ b/target/i386/kvm/kvm.c
> >> @@ -1216,13 +1216,22 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
> >>   * of 'hv_passthrough' mode and fills the environment with all supported
> >>   * Hyper-V features.
> >>   */
> >> -static void hyperv_expand_features(CPUState *cs, Error **errp)
> >> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
> >>  {
> >> -    X86CPU *cpu = X86_CPU(cs);
> >> +    CPUState *cs = CPU(cpu);
> >>  
> >>      if (!hyperv_enabled(cpu))
> >>          return;
> >>  
> >> +    /*
> >> +     * When kvm_hyperv_expand_features is called at CPU feature expansion
> >> +     * time per-CPU kvm_state is not available yet so we can only proceed
> >> +     * when KVM_CAP_SYS_HYPERV_CPUID is supported.
> >> +     */
> >> +    if (!cs->kvm_state &&
> >> +        !kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID))
> >> +        return;
> >> +
> >>      if (cpu->hyperv_passthrough) {
> >>          cpu->hyperv_vendor_id[0] =
> >>              hv_cpuid_get_host(cs, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, R_EBX);
> >> @@ -1556,7 +1565,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
> >>      env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
> >>  
> >>      /* Paravirtualization CPUIDs */
> >> -    hyperv_expand_features(cs, &local_err);
> >> +    kvm_hyperv_expand_features(cpu, &local_err);
> >
> > Do we still need to call the function again here?
> >
> > If the first expansion isn't expanding everything, I'm afraid
> > this second call will hide bugs in query-cpu-model-expansion.
> >
> 
> The first expansion will do nothing if KVM_CAP_SYS_HYPERV_CPUID is not
> supported, calling it here allows us to proceed. The series makes
> 'query-cpu-model-expansion' output correct only with
> KVM_CAP_SYS_HYPERV_CPUID, without it we don't seem to be able to do much
> (unless we decide to create a 'scratch' CPU or something like that).

Oh, I see.  I suggest adding a comment explaining that.
Developers might be tempted to delete it and not notice it breaks
under older kernels.

-- 
Eduardo
Re: [PATCH v6 15/19] i386: expand Hyper-V features during CPU feature expansion time
Posted by Vitaly Kuznetsov 4 years, 8 months ago 
Eduardo Habkost <ehabkost@redhat.com> writes:

> On Mon, May 24, 2021 at 02:13:09PM +0200, Vitaly Kuznetsov wrote:
> [...]
>> >> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
>> >> index a42263b24fca..d5551c4ab5cf 100644
>> >> --- a/target/i386/kvm/kvm.c
>> >> +++ b/target/i386/kvm/kvm.c
>> >> @@ -1216,13 +1216,22 @@ static uint32_t hv_build_cpuid_leaf(CPUState *cs, uint32_t func, int reg)
>> >>   * of 'hv_passthrough' mode and fills the environment with all supported
>> >>   * Hyper-V features.
>> >>   */
>> >> -static void hyperv_expand_features(CPUState *cs, Error **errp)
>> >> +void kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
>> >>  {
>> >> -    X86CPU *cpu = X86_CPU(cs);
>> >> +    CPUState *cs = CPU(cpu);
>> >>  
>> >>      if (!hyperv_enabled(cpu))
>> >>          return;
>> >>  
>> >> +    /*
>> >> +     * When kvm_hyperv_expand_features is called at CPU feature expansion
>> >> +     * time per-CPU kvm_state is not available yet so we can only proceed
>> >> +     * when KVM_CAP_SYS_HYPERV_CPUID is supported.
>> >> +     */
>> >> +    if (!cs->kvm_state &&
>> >> +        !kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID))
>> >> +        return;
>> >> +
>> >>      if (cpu->hyperv_passthrough) {
>> >>          cpu->hyperv_vendor_id[0] =
>> >>              hv_cpuid_get_host(cs, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, R_EBX);
>> >> @@ -1556,7 +1565,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
>> >>      env->apic_bus_freq = KVM_APIC_BUS_FREQUENCY;
>> >>  
>> >>      /* Paravirtualization CPUIDs */
>> >> -    hyperv_expand_features(cs, &local_err);
>> >> +    kvm_hyperv_expand_features(cpu, &local_err);
>> >
>> > Do we still need to call the function again here?
>> >
>> > If the first expansion isn't expanding everything, I'm afraid
>> > this second call will hide bugs in query-cpu-model-expansion.
>> >
>> 
>> The first expansion will do nothing if KVM_CAP_SYS_HYPERV_CPUID is not
>> supported, calling it here allows us to proceed. The series makes
>> 'query-cpu-model-expansion' output correct only with
>> KVM_CAP_SYS_HYPERV_CPUID, without it we don't seem to be able to do much
>> (unless we decide to create a 'scratch' CPU or something like that).
>
> Oh, I see.  I suggest adding a comment explaining that.
> Developers might be tempted to delete it and not notice it breaks
> under older kernels.

Will do, thanks!

-- 
Vitaly

Patchew 2.1-devel-b67e4c2

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