Re: [Xen-devel] [PATCH v5 09/11] xen: add capability to load initrd outside of initial mapping

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Fri, Feb 26, 2016 at 03:28:21PM +0100, Juergen Gross wrote:
> On 26/02/16 15:00, Daniel Kiper wrote:
> > On Thu, Feb 25, 2016 at 04:33:46PM +0100, Juergen Gross wrote:
> >> On 25/02/16 13:47, Daniel Kiper wrote:
> >>> On Thu, Feb 25, 2016 at 12:33:35PM +0100, Juergen Gross wrote:
> >>>> Modern pvops linux kernels support an initrd not covered by the initial
> >>>> mapping. This capability is flagged by an elf-note.
> >>>>
> >>>> In case the elf-note is set by the kernel don't place the initrd into
> >>>> the initial mapping. This will allow to load larger initrds and/or
> >>>> support domains with larger memory, as the initial mapping is limited
> >>>> to 2GB and it is containing the p2m list.
> >>>>
> >>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> >>>> ---
> >>>> V5: let call grub_xen_alloc_final() all subfunctions unconditionally
> >>>>     and let them decide whether they need to do anything
> >>>> V4: rename grub_xen_alloc_end() to grub_xen_alloc_final()
> >>>> ---
> >>>>  grub-core/loader/i386/xen.c        | 65 
> >>>> ++++++++++++++++++++++++++++++--------
> >>>>  grub-core/loader/i386/xen_fileXX.c |  3 ++
> >>>>  include/grub/xen_file.h            |  1 +
> >>>>  3 files changed, 56 insertions(+), 13 deletions(-)
> >>>>
> >>>> diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
> >>>> index 2e12763..466f0c0 100644
> >>>> --- a/grub-core/loader/i386/xen.c
> >>>> +++ b/grub-core/loader/i386/xen.c
> >>>> @@ -228,6 +228,9 @@ grub_xen_p2m_alloc (void)
> >>>>    grub_size_t p2msize;
> >>>>    grub_err_t err;
> >>>>
> >>>> +  if (xen_state.virt_mfn_list)
> >>>> +    return GRUB_ERR_NONE;
> >>>> +
> >>>>    xen_state.state.mfn_list = xen_state.max_addr;
> >>>>    xen_state.next_start.mfn_list =
> >>>>      xen_state.max_addr + xen_state.xen_inf.virt_base;
> >>>> @@ -250,6 +253,9 @@ grub_xen_special_alloc (void)
> >>>>    grub_relocator_chunk_t ch;
> >>>>    grub_err_t err;
> >>>>
> >>>> +  if (xen_state.virt_start_info)
> >>>> +    return GRUB_ERR_NONE;
> >>>> +
> >>>>    err = grub_relocator_alloc_chunk_addr (xen_state.relocator, &ch,
> >>>>                                           xen_state.max_addr,
> >>>>                                           sizeof (xen_state.next_start));
> >>>> @@ -281,6 +287,9 @@ grub_xen_pt_alloc (void)
> >>>>    grub_uint64_t nr_info_pages;
> >>>>    grub_uint64_t nr_pages, nr_pt_pages, nr_need_pages;
> >>>>
> >>>> +  if (xen_state.virt_pgtable)
> >>>> +    return GRUB_ERR_NONE;
> >>>> +
> >>>>    xen_state.next_start.pt_base =
> >>>>      xen_state.max_addr + xen_state.xen_inf.virt_base;
> >>>>    xen_state.state.paging_start = xen_state.max_addr >> PAGE_SHIFT;
> >>>> @@ -320,6 +329,24 @@ grub_xen_pt_alloc (void)
> >>>>  }
> >>>>
> >>>>  static grub_err_t
> >>>> +grub_xen_alloc_final (void)
> >>>> +{
> >>>> +  grub_err_t err;
> >>>> +
> >>>> +  err = grub_xen_p2m_alloc ();
> >>>> +  if (err)
> >>>> +    return err;
> >>>> +  err = grub_xen_special_alloc ();
> >>>> +  if (err)
> >>>> +    return err;
> >>>> +  err = grub_xen_pt_alloc ();
> >>>> +  if (err)
> >>>> +    return err;
> >>>
> >>> Could you move grub_xen_p2m_alloc() here? This way grub_xen_alloc_final()
> >>> will be real final in patch 11 and you do not need an extra condition
> >>> around grub_xen_p2m_alloc().
> >>
> >> No. Page tables must be allocated after p2m unless p2m is outside of
> >> initial kernel mapping (patch 11).
> >
> > OK, I was afraid of that. However, then grub_xen_alloc_final() is not final.
>
> Sure it is. Patch 11 just adds allocation to grub_xen_alloc_final(), not
> after it.

Excerpt from patch 11:

@@ -474,6 +503,12 @@ grub_xen_boot (void)
   err = grub_xen_alloc_final ();
   if (err)
     return err;
+  if (xen_state.xen_inf.has_p2m_base)
+    {
+      err = grub_xen_p2m_alloc ();
+      if (err)
+        return err;
+    }

> > So, maybe it should be called grub_xen_alloc_boot_data() or something like 
> > that.

Then my previous comment is still valid.

Daniel

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