[PATCH v1 0/1] hyperv: Enable SCONTROL if SYNIC is enabled

[PATCH v1 0/1] hyperv: Enable SCONTROL if SYNIC is enabled

[Jon Doron]

Based on an analysis of the HyperV firmwares (Gen1 and Gen2) it seems
like the SCONTROL is not being set to the ENABLED state as like we have
thought.

Also from a test done by Vitaly Kuznetsov, running a nested HyperV it
was concluded that the first access to the SCONTROL MSR with a read
resulted with the value of 0x1, aka HV_SYNIC_CONTROL_ENABLE.

It's important to note that this diverges from the value states in the
HyperV TLFS of 0.

Jon Doron (1):
  hyperv: Enable SCONTROL if SYNIC is enabled

 target/i386/kvm.c | 2 ++
 1 file changed, 2 insertions(+)

-- 
2.24.1

[PATCH v1 1/1] hyperv: Enable SCONTROL if SYNIC is enabled

[Jon Doron]

Based on an analysis of the HyperV firmwares (Gen1 and Gen2) it seems
like the SCONTROL is not being set to the ENABLED state as like we have
thought.

Also from a test done by Vitaly Kuznetsov, running a nested HyperV it
was concluded that the first access to the SCONTROL MSR with a read
resulted with the value of 0x1, aka HV_SYNIC_CONTROL_ENABLE.

It's important to note that this diverges from the value states in the
HyperV TLFS of 0.

Signed-off-by: Jon Doron <arilou@gmail.com>
---
 target/i386/kvm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index b8455c89ed..6a62e8ae94 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -1904,6 +1904,8 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
 
     if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNIC)) {
         int i;
+
+        env->msr_hv_synic_control = HV_SYNIC_ENABLE;
         for (i = 0; i < ARRAY_SIZE(env->msr_hv_synic_sint); i++) {
             env->msr_hv_synic_sint[i] = HV_SINT_MASKED;
         }
-- 
2.24.1

Re: [PATCH v1 1/1] hyperv: Enable SCONTROL if SYNIC is enabled

[Paolo Bonzini]

On 17/07/20 14:56, Jon Doron wrote:
> Based on an analysis of the HyperV firmwares (Gen1 and Gen2) it seems
> like the SCONTROL is not being set to the ENABLED state as like we have
> thought.
> 
> Also from a test done by Vitaly Kuznetsov, running a nested HyperV it
> was concluded that the first access to the SCONTROL MSR with a read
> resulted with the value of 0x1, aka HV_SYNIC_CONTROL_ENABLE.
> 
> It's important to note that this diverges from the value states in the
> HyperV TLFS of 0.
> 
> Signed-off-by: Jon Doron <arilou@gmail.com>
> ---
>  target/i386/kvm.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index b8455c89ed..6a62e8ae94 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1904,6 +1904,8 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
>  
>      if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNIC)) {
>          int i;
> +
> +        env->msr_hv_synic_control = HV_SYNIC_ENABLE;
>          for (i = 0; i < ARRAY_SIZE(env->msr_hv_synic_sint); i++) {
>              env->msr_hv_synic_sint[i] = HV_SINT_MASKED;
>          }
> 

Are both patches needed or only the Hyper-V one?

Paolo

Re: [PATCH v1 1/1] hyperv: Enable SCONTROL if SYNIC is enabled

[Jon Doron]

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I think both patches are

On Mon, Aug 10, 2020, 20:27 Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 17/07/20 14:56, Jon Doron wrote:
> > Based on an analysis of the HyperV firmwares (Gen1 and Gen2) it seems
> > like the SCONTROL is not being set to the ENABLED state as like we have
> > thought.
> >
> > Also from a test done by Vitaly Kuznetsov, running a nested HyperV it
> > was concluded that the first access to the SCONTROL MSR with a read
> > resulted with the value of 0x1, aka HV_SYNIC_CONTROL_ENABLE.
> >
> > It's important to note that this diverges from the value states in the
> > HyperV TLFS of 0.
> >
> > Signed-off-by: Jon Doron <arilou@gmail.com>
> > ---
> >  target/i386/kvm.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> > index b8455c89ed..6a62e8ae94 100644
> > --- a/target/i386/kvm.c
> > +++ b/target/i386/kvm.c
> > @@ -1904,6 +1904,8 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
> >
> >      if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNIC)) {
> >          int i;
> > +
> > +        env->msr_hv_synic_control = HV_SYNIC_ENABLE;
> >          for (i = 0; i < ARRAY_SIZE(env->msr_hv_synic_sint); i++) {
> >              env->msr_hv_synic_sint[i] = HV_SINT_MASKED;
> >          }
> >
>
> Are both patches needed or only the Hyper-V one?
>
> Paolo
>
>

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