Re: [Xen-devel] [PATCH v2 4/6] xen: add capability to load initrd outside of initial mapping

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Thu, Feb 11, 2016 at 08:53:24AM +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>
> ---
>  grub-core/loader/i386/xen.c        | 56 
> ++++++++++++++++++++++++++++++--------
>  grub-core/loader/i386/xen_fileXX.c |  3 ++
>  include/grub/xen_file.h            |  1 +
>  3 files changed, 49 insertions(+), 11 deletions(-)
>
> diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
> index 65cec27..0f41048 100644
> --- a/grub-core/loader/i386/xen.c
> +++ b/grub-core/loader/i386/xen.c
> @@ -307,15 +307,14 @@ grub_xen_pt_alloc (void)
>  }
>
>  static grub_err_t
> -grub_xen_boot (void)
> +grub_xen_alloc_end (void)
>  {
>    grub_err_t err;
> -  grub_uint64_t nr_pages;
> -  struct gnttab_set_version gnttab_setver;
> -  grub_size_t i;
> +  static int called = 0;
>
> -  if (grub_xen_n_allocated_shared_pages)
> -    return grub_error (GRUB_ERR_BUG, "active grants");
> +  if (called)
> +    return GRUB_ERR_NONE;

Why?

> +  called = 1;
>
>    err = grub_xen_p2m_alloc ();
>    if (err)
> @@ -327,6 +326,24 @@ grub_xen_boot (void)
>    if (err)
>      return err;
>
> +  return GRUB_ERR_NONE;
> +}
> +
> +static grub_err_t
> +grub_xen_boot (void)
> +{
> +  grub_err_t err;
> +  grub_uint64_t nr_pages;
> +  struct gnttab_set_version gnttab_setver;
> +  grub_size_t i;
> +
> +  if (grub_xen_n_allocated_shared_pages)
> +    return grub_error (GRUB_ERR_BUG, "active grants");

Why?

> +  err = grub_xen_alloc_end ();
> +  if (err)
> +    return err;
> +
>    err = set_mfns (console_pfn);
>    if (err)
>      return err;
> @@ -587,6 +604,13 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ 
> ((unused)),
>        goto fail;
>      }
>
> +  if (xen_inf.unmapped_initrd)
> +    {
> +      err = grub_xen_alloc_end ();
> +      if (err)
> +        goto fail;
> +    }
> +
>    if (grub_initrd_init (argc, argv, &initrd_ctx))
>      goto fail;
>
> @@ -603,13 +627,22 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ 
> ((unused)),
>       goto fail;
>      }
>
> -  next_start.mod_start = max_addr + xen_inf.virt_base;
> -  next_start.mod_len = size;
> -
> -  max_addr = ALIGN_UP (max_addr + size, PAGE_SIZE);
> +  if (xen_inf.unmapped_initrd)
> +    {
> +      next_start.flags |= SIF_MOD_START_PFN;
> +      next_start.mod_start = max_addr >> PAGE_SHIFT;
> +      next_start.mod_len = size;
> +    }
> +  else
> +    {
> +      next_start.mod_start = max_addr + xen_inf.virt_base;
> +      next_start.mod_len = size;
> +    }
>
>    grub_dprintf ("xen", "Initrd, addr=0x%x, size=0x%x\n",
> -             (unsigned) next_start.mod_start, (unsigned) size);
> +             (unsigned) (max_addr + xen_inf.virt_base), (unsigned) size);
> +
> +  max_addr = ALIGN_UP (max_addr + size, PAGE_SIZE);
>
>  fail:
>    grub_initrd_close (&initrd_ctx);
> @@ -660,6 +693,7 @@ grub_cmd_module (grub_command_t cmd __attribute__ 
> ((unused)),
>
>    if (!xen_module_info_page)
>      {
> +      xen_inf.unmapped_initrd = 0;
>        n_modules = 0;
>        max_addr = ALIGN_UP (max_addr, PAGE_SIZE);
>        modules_target_start = max_addr;
> diff --git a/grub-core/loader/i386/xen_fileXX.c 
> b/grub-core/loader/i386/xen_fileXX.c
> index 1ba5649..69fccd2 100644
> --- a/grub-core/loader/i386/xen_fileXX.c
> +++ b/grub-core/loader/i386/xen_fileXX.c
> @@ -253,6 +253,9 @@ parse_note (grub_elf_t elf, struct grub_xen_file_info *xi,
>                                         descsz == 2 ? 2 : 3) == 0)
>           xi->arch = GRUB_XEN_FILE_I386;
>         break;
> +     case 16:

Could you define this a constant and use it here?

Daniel

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