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Re: [PATCH] x86/hypercall: fix gnttab hypercall args conditional build on pvshim
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Fri, 8 Jan 2021 16:27:47 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
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On Fri, Jan 08, 2021 at 04:24:01PM +0100, Jan Beulich wrote:
> 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>
Thanks.
In fact I'm not sure it's helpful to have any build time conditionals
in hypercall_args_table, but let's leave that for another fix.
Roger.
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