Re: [Xen-devel] [PATCH v2 16/17] libxc/xc_dom_arm: Copy ACPI tables to guest space

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 23 Jun 2016, Julien Grall wrote:
> Hi Shannon,
> 
> On 23/06/2016 04:17, Shannon Zhao wrote:
> > From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> > 
> > Copy all the ACPI tables to guest space so that UEFI or guest could
> > access them.
> > 
> > Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> > ---
> >  tools/libxc/xc_dom_arm.c | 51
> > ++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 51 insertions(+)
> > 
> > diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
> > index 64a8b67..6a0a5b7 100644
> > --- a/tools/libxc/xc_dom_arm.c
> > +++ b/tools/libxc/xc_dom_arm.c
> > @@ -63,6 +63,47 @@ static int setup_pgtables_arm(struct xc_dom_image *dom)
> > 
> >  /* ------------------------------------------------------------------------
> > */
> > 
> > +static int xc_dom_copy_acpi(struct xc_dom_image *dom)
> > +{
> > +    int rc, i;
> > +    uint32_t pages_num = ROUNDUP(dom->acpitable_size, XC_PAGE_SHIFT) >>
> > +                         XC_PAGE_SHIFT;
> > +    const xen_pfn_t base = GUEST_ACPI_BASE >> XC_PAGE_SHIFT;
> > +    xen_pfn_t *p2m;
> > +    void *acpi_pages;
> > +
> > +    p2m = malloc(pages_num * sizeof(*p2m));
> > +    for (i = 0; i < pages_num; i++)
> > +        p2m[i] = base + i;
> > +
> > +    rc = xc_domain_populate_physmap_exact(dom->xch, dom->guest_domid,
> > +                                          pages_num, 0, 0, p2m);
> 
> Hmmmm... it looks like this is working because libxl is setting the maximum
> size of the domain with some slack (1MB). However, I guess the slack was for
> something else. Wei, Stefano, Ian, can you confirm?

If I recall correctly, the slack is a magic value coming from the
ancient history of toolstacks.

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