Re: [PATCH v6 06/19] i386: introduce hv_cpuid_get_host()

[Eduardo Habkost]

On Thu, Apr 22, 2021 at 06:11:17PM +0200, Vitaly Kuznetsov wrote:
> As a preparation to implementing hv_cpuid_cache intro introduce
> hv_cpuid_get_host(). No functional change intended.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  target/i386/kvm/kvm.c | 102 +++++++++++++++++++++++-------------------
>  1 file changed, 57 insertions(+), 45 deletions(-)
> 
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index ba093dba4d23..7aeb704b016e 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -1107,6 +1107,19 @@ static int hv_cpuid_get_fw(struct kvm_cpuid2 *cpuid, 
> int fw, uint32_t *r)
>      return 0;
>  }
>  
> +static uint32_t hv_cpuid_get_host(struct kvm_cpuid2 *cpuid, uint32_t func,
> +                                  int reg)
> +{
> +    struct kvm_cpuid_entry2 *entry;
> +
> +    entry = cpuid_find_entry(cpuid, func, 0);
> +    if (!entry) {
> +        return 0;

One possible difference here is that leaves not supported by the
host will now be zeroed out.

...which I expected to be the correct behavior of hv-passthrough,
so:

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>


> +    }
> +
> +    return cpuid_entry_get_reg(entry, reg);
> +}
> +
>  static bool hyperv_feature_supported(struct kvm_cpuid2 *cpuid, int feature)
>  {
>      uint32_t r, fw, bits;
> @@ -1203,7 +1216,7 @@ static int hyperv_handle_properties(CPUState *cs,
>  {
>      X86CPU *cpu = X86_CPU(cs);
>      struct kvm_cpuid2 *cpuid;
> -    struct kvm_cpuid_entry2 *c, *c2;
> +    struct kvm_cpuid_entry2 *c;
>      uint32_t cpuid_i = 0;
>      int r;
>  
> @@ -1235,46 +1248,47 @@ static int hyperv_handle_properties(CPUState *cs,
>      }
>  
>      if (cpu->hyperv_passthrough) {
> -        c = cpuid_find_entry(cpuid, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, 0);
> -        if (c) {
> -            cpu->hyperv_vendor_id[0] = c->ebx;
> -            cpu->hyperv_vendor_id[1] = c->ecx;
> -            cpu->hyperv_vendor_id[2] = c->edx;
> -            cpu->hyperv_vendor = g_realloc(cpu->hyperv_vendor,
> -                                           sizeof(cpu->hyperv_vendor_id) + 
> 1);
> -            memcpy(cpu->hyperv_vendor, cpu->hyperv_vendor_id,
> -                   sizeof(cpu->hyperv_vendor_id));
> -            cpu->hyperv_vendor[sizeof(cpu->hyperv_vendor_id)] = 0;
> -        }
> -
> -        c = cpuid_find_entry(cpuid, HV_CPUID_INTERFACE, 0);
> -        if (c) {
> -            cpu->hyperv_interface_id[0] = c->eax;
> -            cpu->hyperv_interface_id[1] = c->ebx;
> -            cpu->hyperv_interface_id[2] = c->ecx;
> -            cpu->hyperv_interface_id[3] = c->edx;
> -        }
> -
> -        c = cpuid_find_entry(cpuid, HV_CPUID_VERSION, 0);
> -        if (c) {
> -            cpu->hyperv_version_id[0] = c->eax;
> -            cpu->hyperv_version_id[1] = c->ebx;
> -            cpu->hyperv_version_id[2] = c->ecx;
> -            cpu->hyperv_version_id[3] = c->edx;
> -        }
> -
> -        c = cpuid_find_entry(cpuid, HV_CPUID_IMPLEMENT_LIMITS, 0);
> -        if (c) {
> -            cpu->hv_max_vps = c->eax;
> -            cpu->hyperv_limits[0] = c->ebx;
> -            cpu->hyperv_limits[1] = c->ecx;
> -            cpu->hyperv_limits[2] = c->edx;
> -        }
> -
> -        c = cpuid_find_entry(cpuid, HV_CPUID_ENLIGHTMENT_INFO, 0);
> -        if (c) {
> -            cpu->hyperv_spinlock_attempts = c->ebx;
> -        }
> +        cpu->hyperv_vendor_id[0] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, 
> R_EBX);
> +        cpu->hyperv_vendor_id[1] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, 
> R_ECX);
> +        cpu->hyperv_vendor_id[2] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, 
> R_EDX);
> +        cpu->hyperv_vendor = g_realloc(cpu->hyperv_vendor,
> +                                       sizeof(cpu->hyperv_vendor_id) + 1);
> +        memcpy(cpu->hyperv_vendor, cpu->hyperv_vendor_id,
> +               sizeof(cpu->hyperv_vendor_id));
> +        cpu->hyperv_vendor[sizeof(cpu->hyperv_vendor_id)] = 0;
> +
> +        cpu->hyperv_interface_id[0] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_INTERFACE, R_EAX);
> +        cpu->hyperv_interface_id[1] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_INTERFACE, R_EBX);
> +        cpu->hyperv_interface_id[2] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_INTERFACE, R_ECX);
> +        cpu->hyperv_interface_id[3] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_INTERFACE, R_EDX);
> +
> +        cpu->hyperv_version_id[0] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_VERSION, R_EAX);
> +        cpu->hyperv_version_id[1] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_VERSION, R_EBX);
> +        cpu->hyperv_version_id[2] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_VERSION, R_ECX);
> +        cpu->hyperv_version_id[3] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_VERSION, R_EDX);
> +
> +        cpu->hv_max_vps = hv_cpuid_get_host(cpuid, HV_CPUID_IMPLEMENT_LIMITS,
> +                                            R_EAX);
> +        cpu->hyperv_limits[0] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_IMPLEMENT_LIMITS, R_EBX);
> +        cpu->hyperv_limits[1] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_IMPLEMENT_LIMITS, R_ECX);
> +        cpu->hyperv_limits[2] =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_IMPLEMENT_LIMITS, R_EDX);
> +
> +        cpu->hyperv_spinlock_attempts =
> +            hv_cpuid_get_host(cpuid, HV_CPUID_ENLIGHTMENT_INFO, R_EBX);
>      }
>  
>      /* Features */
> @@ -1348,10 +1362,8 @@ static int hyperv_handle_properties(CPUState *cs,
>      if (cpu->hyperv_no_nonarch_cs == ON_OFF_AUTO_ON) {
>          c->eax |= HV_NO_NONARCH_CORESHARING;
>      } else if (cpu->hyperv_no_nonarch_cs == ON_OFF_AUTO_AUTO) {
> -        c2 = cpuid_find_entry(cpuid, HV_CPUID_ENLIGHTMENT_INFO, 0);
> -        if (c2) {
> -            c->eax |= c2->eax & HV_NO_NONARCH_CORESHARING;
> -        }
> +        c->eax |= hv_cpuid_get_host(cpuid, HV_CPUID_ENLIGHTMENT_INFO, R_EAX) 
> &
> +            HV_NO_NONARCH_CORESHARING;
>      }
>  
>      c = &cpuid_ent[cpuid_i++];
> -- 
> 2.30.2
> 

-- 
Eduardo