Re: [Xen-devel] [PATCH v4 09/11] xen: add capability to load initrd outside of initial mapping

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Mon, Feb 22, 2016 at 07:03:17AM +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>
> Reviewed-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> ---
> V4: rename grub_xen_alloc_end() to grub_xen_alloc_final()
> ---
>  grub-core/loader/i386/xen.c        | 61 
> ++++++++++++++++++++++++++++++--------
>  grub-core/loader/i386/xen_fileXX.c |  3 ++
>  include/grub/xen_file.h            |  1 +
>  3 files changed, 52 insertions(+), 13 deletions(-)
>
> diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
> index 2e12763..22a94ae 100644
> --- a/grub-core/loader/i386/xen.c
> +++ b/grub-core/loader/i386/xen.c
> @@ -58,6 +58,7 @@ struct xen_loader_state {
>    grub_uint64_t modules_target_start;
>    grub_size_t n_modules;
>    int loaded;
> +  int alloc_end_called;

alloc_end_called -> alloc_final_called

>  };
>
>  static struct xen_loader_state xen_state;
> @@ -320,6 +321,28 @@ grub_xen_pt_alloc (void)
>  }
>
>  static grub_err_t
> +grub_xen_alloc_final (void)
> +{
> +  grub_err_t err;
> +
> +  if (xen_state.alloc_end_called)
> +    return GRUB_ERR_NONE;
> +  xen_state.alloc_end_called = 1;

This is not nice. What happens if grub_xen_p2m_alloc() allocate what
is needed and grub_xen_special_alloc() fails?

Maybe grub_xen_p2m_alloc(), grub_xen_special_alloc() and grub_xen_pt_alloc()
should check itself that required regions are allocated properly
(if (something != NULL)) and do nothing if yes.

Daniel

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