Re: [PATCH v3] xen/x86/pvh: handle ACPI RSDT table in PVH Dom0 build

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Apr 25, 2024 at 08:12:09AM +0200, Jan Beulich wrote:
> On 24.04.2024 21:18, Daniel P. Smith wrote:
> > @@ -1089,6 +1098,9 @@ static int __init pvh_setup_acpi_xsdt(struct domain *d, paddr_t madt_addr,
> >      xsdt->header = *table;
> >      acpi_os_unmap_memory(table, sizeof(*table));
> >  
> > +    /* In case the header is an RSDT copy, blindly ensure it has an XSDT sig */
> > +    xsdt->header.signature[0] = 'X';
> 
> This is in no way "blindly". The size of the table elements being different
> between RSDT and XSDT makes it mandatory to have the correct signature. Else
> the consumer of the struct is going to be misled.

The "blindly" IMO refers to the fact that the table might already have
the right signature, but this is not checked, IOW we could do:

if ( xsdt->header.signature[0] == 'R' )
    xsdt->header.signature[0] = 'X';

Regards, Roger.