Re: [Xen-devel] [PATCH RESEND 03/14] libxc: Add placeholders for ACPI tables blob and size

[Julien Grall <julien.grall@xxxxxxx>]

On 07/06/16 12:13, Shannon Zhao wrote:
> On 2016/6/7 19:05, Julien Grall wrote:
> > Hello Shannon,
> >
> > On 31/05/16 06:02, Shannon Zhao wrote:
> > > From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> > >
> > > Currently it only needs ACPI table RSDP, XSDT, GTDT, MADT, FADT, DSDT
> > > for ARM VM. So only add placeholders for them here.
> > >
> > > Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> > > ---
> > >    tools/libxc/include/xc_dom.h | 17 +++++++++++++++++
> > >    1 file changed, 17 insertions(+)
> > >
> > > diff --git a/tools/libxc/include/xc_dom.h b/tools/libxc/include/xc_dom.h
> > > index 6cb10c4..0fe54dd 100644
> > > --- a/tools/libxc/include/xc_dom.h
> > > +++ b/tools/libxc/include/xc_dom.h
> > > @@ -56,6 +56,20 @@ struct xc_dom_phys {
> > >        xen_pfn_t count;
> > >    };
> > >
> > > +struct acpitable {
> > > +    void *table;
> > > +    size_t size;
> > > +};
> > > +
> > > +struct acpitable_blob {
> > > +    struct acpitable rsdp;
> > > +    struct acpitable xsdt;
> > > +    struct acpitable gtdt;
> > > +    struct acpitable madt;
> > > +    struct acpitable fadt;
> > > +    struct acpitable dsdt;
> > > +};
> > Is there any particular reason to expose the list of the tables outside
> > of the building code?
> >
> > I would provide a single buffer with all the tables inside. Similar to
> > what you did for building the tables in the hypervisor.
> When it loads these tables to guest memory space, it needs to update the
> entries (pointing to other tables) of XSDT and also the
> xsdt_physical_address in RSDP.
Why can't we load the ACPI tables at an hardcoded place in the memory 
(for instance always at the beginning of the RAM)?
This would make the code a lot simpler and would avoid a duplication of 
the same 5 lines for each tables in patch 14:
+        xsdt = (struct acpi_xsdt_descriptor *)acpitablemap;
+        memcpy(acpitablemap, dom->acpitable_blob->xsdt.table,
+               dom->acpitable_blob->xsdt.size);

[...]

+        start += dom->acpitable_blob->xsdt.size;
+        acpitablemap += dom->acpitable_blob->xsdt.size;

Regards,

--
Julien Grall

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