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

[Wei Liu <wl@xxxxxxx>]

On Fri, Jan 31, 2020 at 03:12:50PM +0100, Jan Beulich wrote:
> On 30.01.2020 13:28, 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.
> 
> I guess I need an explanation here. Aiui you don't really need
> the definition to be in the linker script, and it could as well
> be in e.g. assembly code. How does the same .equ approach not
> work in this case?
> 

In commit message:

mm.c:5736:5: error: invalid 'asm': operand is not a condition code,
invalid operand code 'c'
               asm ( ".equ HV_HCALL_PAGE, %c0; .global HV_HCALL_PAGE"

ISTR you once mentioned in IRC that there is a way around this (with a
new modifier / qualifier), but I don't have the log anymore.

> Also I think the above will trigger the warnings Andrew had
> mentioned (on irc?) from the code generating xen.efi's runtime
> relocation table. Just like in
> 

It was a reply to v4.  <cb0e82dc-a154-f918-e725-f77913f835f9@xxxxxxxxxx>

I don't see the warning with this patch.

Wei.

> ASSERT(__2M_rwdata_end <= XEN_VIRT_END - XEN_VIRT_START + __XEN_VIRT_START -
>                           NR_CPUS * PAGE_SIZE,
>        "Xen image overlaps stubs area")
> 
> I think you need to adjust by __XEN_VIRT_START - XEN_VIRT_START.
> 
> Jan

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