Re: [Xen-devel] [PATCH v5 08/12] x86/hyperv: provide Hyper-V hypercall functions

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Jan 30, 2020 at 12:39:20PM +0000, Wei Liu wrote:
> On Thu, Jan 30, 2020 at 01:32:26PM +0100, Roger Pau Monné wrote:
> > On Thu, Jan 30, 2020 at 12:28:36PM +0000, Wei Liu wrote:
> > > On Thu, Jan 30, 2020 at 01:08:07PM +0100, Roger Pau Monné wrote:
> > > > 
> > > > > +}
> > > > > +
> > > > >  /*
> > > > >   * Local variables:
> > > > >   * mode: C
> > > > > diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> > > > > index 97f9c07891..8e02b4c648 100644
> > > > > --- a/xen/arch/x86/xen.lds.S
> > > > > +++ b/xen/arch/x86/xen.lds.S
> > > > > @@ -329,6 +329,10 @@ SECTIONS
> > > > >    efi = .;
> > > > >  #endif
> > > > >  
> > > > > +#ifdef CONFIG_HYPERV_GUEST
> > > > > +  hv_hcall_page = ABSOLUTE(__fix_x_to_virt(1));
> > > > 
> > > > I assume there's no way to use FIX_X_HYPERV_HCALL because it's an
> > > > enum?
> > > > 
> > > 
> > > Yes.
> > > 
> > > And the trick to generate a symbol didn't work either.
> > 
> > And you must define that symbol in the linker script? It doesn't seem
> > to be used at link time.
> > 
> 
> I don't follow. I wish I could define and use a symbol in the linker
> script but couldn't.

It's likely my fault, as I haven't been following the patch series in
that much detail. I assume this is done in order to generate better
code, rather than doing something like:

void *hv_hcall_page = fix_x_to_virt(FIX_X_HYPERV_HCALL);

In a C file somewhere when the hypercall page is setup?

Thanks, Roger.

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