Re: [Xen-devel] [PATCH v5 01/28] HYPERCALL_version_op. New hypercall mirroring XENVER_ but sane.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On March 24, 2016 4:22:29 PM EDT, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 
wrote:
>On 24/03/16 20:00, Konrad Rzeszutek Wilk wrote:
>> This hypercall mirrors the XENVER_ in that it has similar
>functionality.
>> However it is designed differently:
>>  - No compat layer. The data structures are the same size on 32
>>    as on 64-bit.
>>  - The hypercall accepts three arguments - the command, pointer to
>>    an buffer, and the length of the buffer.
>
>"a buffer"
>
>> +/* Computed by kernel_cache_init. */
>> +static xen_capabilities_info_t __read_mostly cached_cap;
>> +static unsigned int __read_mostly cached_cap_len;
>> +
>> +/*
>> + * Similar to HYPERVISOR_xen_version but with a sane interface
>> + * (has a length, one can probe for the length) and with one less
>sub-ops:
>> + * missing XENVER_compile_info.
>> + */
>> +DO(version_op)(unsigned int cmd, XEN_GUEST_HANDLE_PARAM(void) arg,
>> +               unsigned int len)
>> +{
>> +    union {
>> +        xen_version_op_val_t val;
>> +        xen_feature_info_t fi;
>> +    } u = {};
>> +    unsigned int sz = 0;
>> +    const void *ptr = NULL;
>> +    int rc = xsm_version_op(XSM_OTHER, cmd);
>> +
>> +    /* We can safely return -EPERM! */
>> +    if ( rc )
>> +        return rc;
>> +
>> +    /*
>> +     * The HYPERVISOR_xen_version differs in that some return the
>value,
>> +     * and some copy it on back on argument. We follow the same rule
>for all
>> +     * sub-ops: return 0 on success, positive value of bytes
>returned, and
>
>You can't return both 0 and a positive number for success.  I would
>recommend "return the number of bytes written, or negative errno on
>failure".

Thanks!

And Argh!

I neglected to change the name of kernel_cache_init as Jan requested.

>
>Other than these, LGTM.
>
>Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>


Yeey!


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