Re: [Xen-devel] [PATCH 3/5] xen/domain: Audit config->max_vcpus during {, arch_}check_domain_config()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 09/10/18 12:23, Julien Grall wrote:
> On 05/10/2018 15:54, Andrew Cooper wrote:
>> ---
>>   xen/arch/arm/domain.c | 18 ++++++++++++++++++
>>   xen/arch/x86/domain.c |  6 ++++++
>>   xen/common/domain.c   |  3 +++
>>   3 files changed, 27 insertions(+)
>>
>> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
>> index 43593a4..9676893 100644
>> --- a/xen/arch/arm/domain.c
>> +++ b/xen/arch/arm/domain.c
>> @@ -601,6 +601,8 @@ void vcpu_switch_to_aarch64_mode(struct vcpu *v)
>>     int arch_check_domain_config(struct xen_domctl_createdomain *config)
>>   {
>> +    unsigned int max_vcpus = 0;
>> +
>>       /* Fill in the native GIC version, passed back to the
>> toolstack. */
>>       if ( config->arch.gic_version == XEN_DOMCTL_CONFIG_GIC_NATIVE )
>>       {
>> @@ -619,6 +621,22 @@ int arch_check_domain_config(struct
>> xen_domctl_createdomain *config)
>>           }
>>       }
>>   +    /* Calculate the maximum number of vcpus from the selected GIC
>> version... */
>> +    switch ( config->arch.gic_version )
>> +    {
>> +    case GIC_V2: max_vcpus = 8;   break;
>> +    case GIC_V3: max_vcpus = 255; break;
>> +
>> +    default:
>> +        return -EOPNOTSUPP;
>> +    }
>
> I would prefer to keep those values in a separate helper implemented
> by each vGIC.

How do you intend that working?  The values can't be hooked off a GIC
object, because we don't have one yet.

>
>> +
>> +    /* ... clipped at the maximum value Xen has been configured for. */
>> +    max_vcpus = min(max_vcpus, MAX_VIRT_CPUS + 0u);
>
> + 0U feels a bit odd to read. It would be better to append u in
> MAX_VIRT_CPUS.

Will do.

~Andrew

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