Re: [PATCH] x86/hypercall: fix gnttab hypercall args conditional build on pvshim

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.01.2021 16:11, Roger Pau Monné wrote:
> On Fri, Jan 08, 2021 at 04:01:52PM +0100, Jan Beulich wrote:
>> On 08.01.2021 15:41, Roger Pau Monne wrote:
>>> --- a/xen/arch/x86/hypercall.c
>>> +++ b/xen/arch/x86/hypercall.c
>>> @@ -47,7 +47,7 @@ const hypercall_args_t 
>>> hypercall_args_table[NR_hypercalls] =
>>>      ARGS(xen_version, 2),
>>>      ARGS(console_io, 3),
>>>      ARGS(physdev_op_compat, 1),
>>> -#ifdef CONFIG_GRANT_TABLE
>>> +#if defined(CONFIG_GRANT_TABLE) || defined(CONFIG_PV_SHIM)
>>>      ARGS(grant_table_op, 3),
>>>  #endif
>>>      ARGS(vm_assist, 2),
>>
>> This is correct when a shim-enabled build runs as shim, but
>> not when it runs as normal hypervisor. Just like the hypercall
>> handler gets patched into the hypercall table (in
>> pv_shim_setup_dom()), the argument count will also want
>> updating there, I think.
> 
> Having the argument count set when the hypercall handler is NULL is
> fine, as Xen won't get into processing hypercall_args_table if the
> handler is NULL.

Oh, good point.

> While it's true that can be fixed at run time in the
> same way that we patch the handler it seems more cumbersome, that's
> why I went for this IMO simpler fix.

Agreed:
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan