Re: [PATCH v5 11/12] xen/arm: add sve property for dom0less domUs

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi,

> On 18 Apr 2023, at 14:55, Bertrand Marquis <Bertrand.Marquis@xxxxxxx> wrote:
> 
> Hi Luca,
> 
>> On 12 Apr 2023, at 11:49, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
>> 
>> Add a device tree property in the dom0less domU configuration
>> to enable the guest to use SVE.
>> 
>> Update documentation.
>> 
>> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
> Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

In fact the doc needs fixing as the domain creation does not fail.
@Luca thanks for mentioning that to me

So please fix that and you can keep my R-b (unless some changes are
needed after the discussion on parameter handling).

Cheers
Bertrand

> 
> Cheers
> Bertrand
> 
>> ---
>> Changes from v4:
>> - Now it is possible to specify the property "sve" for dom0less
>>  device tree node without any value, that means the platform
>>  supported VL will be used.
>> Changes from v3:
>> - Now domainconfig_encode_vl is named sve_encode_vl
>> Changes from v2:
>> - xen_domctl_createdomain field name has changed into sve_vl
>>  and its value is the VL/128, use domainconfig_encode_vl
>>  to encode a plain VL in bits.
>> Changes from v1:
>> - No changes
>> Changes from RFC:
>> - Changed documentation
>> ---
>> docs/misc/arm/device-tree/booting.txt | 11 +++++++++++
>> xen/arch/arm/domain_build.c           | 24 ++++++++++++++++++++++++
>> 2 files changed, 35 insertions(+)
>> 
>> diff --git a/docs/misc/arm/device-tree/booting.txt 
>> b/docs/misc/arm/device-tree/booting.txt
>> index 3879340b5e0a..f9d2ecdda48a 100644
>> --- a/docs/misc/arm/device-tree/booting.txt
>> +++ b/docs/misc/arm/device-tree/booting.txt
>> @@ -193,6 +193,17 @@ with the following properties:
>>    Optional. Handle to a xen,cpupool device tree node that identifies the
>>    cpupool where the guest will be started at boot.
>> 
>> +- sve
>> +
>> +    Optional. A number that, when above 0, enables SVE for this guest and 
>> sets
>> +    its maximum SVE vector length. The default value is 0, that means this
>> +    guest is not allowed to use SVE, the maximum value allowed is 2048, any
>> +    other value must be multiple of 128.
>> +    Please note that if the platform supports a lower value of bits, then 
>> the
>> +    domain creation will fail.
>> +    Specifying this property with no value, means that the SVE vector length
>> +    will be set equal to the maximum vector length supported by the 
>> platform.
>> +
>> - xen,enhanced
>> 
>>    A string property. Possible property values are:
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index 3f30ef5c37b6..c1f0d1d78431 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -4004,6 +4004,30 @@ void __init create_domUs(void)
>>            d_cfg.max_maptrack_frames = val;
>>        }
>> 
>> +        if ( dt_get_property(node, "sve", &val) )
>> +        {
>> +            unsigned int sve_vl_bits;
>> +
>> +            if ( !val )
>> +            {
>> +                /* Property found with no value, means max HW VL supported 
>> */
>> +                rc = sve_sanitize_vl_param(-1, &sve_vl_bits);
>> +            }
>> +            else
>> +            {
>> +                if ( dt_property_read_u32(node, "sve", &val) )
>> +                    rc = sve_sanitize_vl_param(val, &sve_vl_bits);
>> +                else
>> +                    panic("Error reading 'sve' property");
>> +            }
>> +
>> +            if ( !rc )
>> +                d_cfg.arch.sve_vl = sve_encode_vl(sve_vl_bits);
>> +            else
>> +                printk(XENLOG_WARNING
>> +                       "SVE vector length error, disable feature for 
>> Dom0less DomU\n");
>> +        }
>> +
>>        /*
>>         * The variable max_init_domid is initialized with zero, so here it's
>>         * very important to use the pre-increment operator to call
>> -- 
>> 2.34.1
>> 
> 
>