Re: [Xen-devel] [PATCH v3 13/16] hvmloader: Load ACPI tables from hvm_start_info module

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Fri, Mar 04, 2016 at 01:39:38AM -0700, Jan Beulich wrote:
> >>> On 03.03.16 at 18:59, <anthony.perard@xxxxxxxxxx> wrote:
> > On Tue, Mar 01, 2016 at 09:17:25AM -0700, Jan Beulich wrote:
> >> >>> On 25.02.16 at 15:56, <anthony.perard@xxxxxxxxxx> wrote:
> >> > --- a/tools/firmware/hvmloader/hvmloader.c
> >> > +++ b/tools/firmware/hvmloader/hvmloader.c
> >> > @@ -365,8 +365,26 @@ int main(void)
> >> >  
> >> >          if ( bios->acpi_build_tables )
> >> >          {
> >> > +            const struct hvm_modlist_entry *acpi_module;
> >> > +            acpi_module = get_module_entry(hvm_start_info, "acpi");
> >> >              printf("Loading ACPI ...\n");
> >> > -            bios->acpi_build_tables();
> >> > +            if ( acpi_module )
> >> > +            {
> >> > +                uint32_t paddr = acpi_module->paddr;
> >> > +                bios->acpi_build_tables((void*)paddr,
> >> > +                                        acpi_module->size);
> >> > +            }
> >> 
> >> Hmm, so far it was the build process which ensured the right ACPI
> >> tables would be used with the corresponding BIOS. The disconnect
> >> that gets introduced here worries me a little, since things having
> >> got out of sync may be rather hard to diagnose (as they may
> >> surface only much later).
> > 
> > So, my ultimate goal with this series was to be able to create a guest with
> > QEMU's Q35 machine, which would need a different ACPI tables.
> > 
> > Also, I would say that the ACPI tables are already disconnected from the
> > thing they describe, the device model QEMU. I don't think there is much
> > information about the BIOS backed into the DSDT table.
> 
> But then why would the Q35 model need a different one? Or the
> other way around, why wouldn't that other one be usable with
> with the current machine type (or more generally, why couldn't
> we have one that fits all machine types we mean to support)?

I have not though about using the same one for both. I could try to change
the tables we have to make it work with both. But that for another time.

Thanks,

-- 
Anthony PERARD

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