Re: [Xen-devel] [PATCH v2] libxl: put RSDP for PVH guest near 4GB

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

On Tue, Dec 19, 2017 at 05:20:41PM +0100, Juergen Gross wrote:
> On 19/12/17 17:11, Roger Pau Monné wrote:
> > On Tue, Dec 19, 2017 at 04:46:37PM +0100, Juergen Gross wrote:
> >> On 19/12/17 16:38, Roger Pau Monné wrote:
> >>> On Fri, Dec 01, 2017 at 03:14:07PM +0100, Juergen Gross wrote:
> >>>> Instead of locating the RSDP table below 1MB put it just below 4GB
> >>>> like the rest of the ACPI tables in case of PVH guests. This will
> >>>> avoid punching more holes than necessary into the memory map.
> >>>>
> >>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> >>>> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> >>>> ---
> >>>>  tools/libxc/xc_dom_hvmloader.c | 2 +-
> >>>>  tools/libxl/libxl_x86_acpi.c   | 5 ++---
> >>>>  2 files changed, 3 insertions(+), 4 deletions(-)
> >>>>
> >>>> diff --git a/tools/libxc/xc_dom_hvmloader.c 
> >>>> b/tools/libxc/xc_dom_hvmloader.c
> >>>> index 59f94e51e5..3f0bd65547 100644
> >>>> --- a/tools/libxc/xc_dom_hvmloader.c
> >>>> +++ b/tools/libxc/xc_dom_hvmloader.c
> >>>> @@ -136,7 +136,7 @@ static int module_init_one(struct xc_dom_image *dom,
> >>>>      struct xc_dom_seg seg;
> >>>>      void *dest;
> >>>>  
> >>>> -    if ( module->length )
> >>>> +    if ( module->length && !module->guest_addr_out )
> >>>
> >>> Isn't that kind of a separate fix? AFAICT this just prevents
> >>> allocating memory if guest_addr_out is already set to a fixed
> >>> position.
> >>
> >> No, this is mandatory, as I have to skip the allocation for PVH, while
> >> HVM guests really want the allocation to take place.
> > 
> > Was this also a problem before? Other ACPI modules also set
> > guest_addr_out, and previously they would also get memory allocated.
> 
> module_init_one() would only be called for the first ACPI module, which
> happens to be the RSDP.

OK, I have to admit I find all this quite confusing. In any case, the
approach seems correct to me.

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks, Roger.

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