Re: [Xen-devel] [PATCH v2 1/6] xen: factor out p2m list allocation into separate function

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Thu, Feb 11, 2016 at 08:53:21AM +0100, Juergen Gross wrote:
> Do the p2m list allocation of the to be loaded kernel in a separate
> function. This will allow doing the p2m list allocation at different
> times of the boot preparations depending on the features the kernel
> is supporting.
>
> While at this remove superfluous setting of first_p2m_pfn and
> nr_p2m_frames as those are needed only in case of the p2m list not
> being mapped by the initial kernel mapping.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>  grub-core/loader/i386/xen.c | 70 
> ++++++++++++++++++++++++++-------------------
>  1 file changed, 40 insertions(+), 30 deletions(-)
>
> diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
> index c4d9689..42ed7c7 100644
> --- a/grub-core/loader/i386/xen.c
> +++ b/grub-core/loader/i386/xen.c
> @@ -52,6 +52,8 @@ static struct grub_xen_file_info xen_inf;
>  static struct xen_multiboot_mod_list *xen_module_info_page;
>  static grub_uint64_t modules_target_start;
>  static grub_size_t n_modules;
> +static struct grub_relocator_xen_state state;
> +static grub_xen_mfn_t *virt_mfn_list;

Do we strongly need this as globals? I suppose that
both of them could be local to grub_xen_boot.

>  #define PAGE_SIZE 4096
>  #define MAX_MODULES (PAGE_SIZE / sizeof (struct xen_multiboot_mod_list))
> @@ -166,7 +168,7 @@ generate_page_table (grub_uint64_t *where, grub_uint64_t 
> paging_start,
>  }
>
>  static grub_err_t
> -set_mfns (grub_xen_mfn_t * new_mfn_list, grub_xen_mfn_t pfn)
> +set_mfns (grub_xen_mfn_t pfn)
>  {
>    grub_xen_mfn_t i, t;
>    grub_xen_mfn_t cn_pfn = -1, st_pfn = -1;
> @@ -175,32 +177,32 @@ set_mfns (grub_xen_mfn_t * new_mfn_list, grub_xen_mfn_t 
> pfn)
>
>    for (i = 0; i < grub_xen_start_page_addr->nr_pages; i++)
>      {
> -      if (new_mfn_list[i] == grub_xen_start_page_addr->console.domU.mfn)
> +      if (virt_mfn_list[i] == grub_xen_start_page_addr->console.domU.mfn)
>       cn_pfn = i;
> -      if (new_mfn_list[i] == grub_xen_start_page_addr->store_mfn)
> +      if (virt_mfn_list[i] == grub_xen_start_page_addr->store_mfn)
>       st_pfn = i;
>      }
>    if (cn_pfn == (grub_xen_mfn_t)-1)
>      return grub_error (GRUB_ERR_BUG, "no console");
>    if (st_pfn == (grub_xen_mfn_t)-1)
>      return grub_error (GRUB_ERR_BUG, "no store");
> -  t = new_mfn_list[pfn];
> -  new_mfn_list[pfn] = new_mfn_list[cn_pfn];
> -  new_mfn_list[cn_pfn] = t;
> -  t = new_mfn_list[pfn + 1];
> -  new_mfn_list[pfn + 1] = new_mfn_list[st_pfn];
> -  new_mfn_list[st_pfn] = t;
> -
> -  m2p_updates[0].ptr = page2offset (new_mfn_list[pfn]) | MMU_MACHPHYS_UPDATE;
> +  t = virt_mfn_list[pfn];
> +  virt_mfn_list[pfn] = virt_mfn_list[cn_pfn];
> +  virt_mfn_list[cn_pfn] = t;
> +  t = virt_mfn_list[pfn + 1];
> +  virt_mfn_list[pfn + 1] = virt_mfn_list[st_pfn];
> +  virt_mfn_list[st_pfn] = t;
> +
> +  m2p_updates[0].ptr = page2offset (virt_mfn_list[pfn]) | 
> MMU_MACHPHYS_UPDATE;
>    m2p_updates[0].val = pfn;
>    m2p_updates[1].ptr =
> -    page2offset (new_mfn_list[pfn + 1]) | MMU_MACHPHYS_UPDATE;
> +    page2offset (virt_mfn_list[pfn + 1]) | MMU_MACHPHYS_UPDATE;
>    m2p_updates[1].val = pfn + 1;
>    m2p_updates[2].ptr =
> -    page2offset (new_mfn_list[cn_pfn]) | MMU_MACHPHYS_UPDATE;
> +    page2offset (virt_mfn_list[cn_pfn]) | MMU_MACHPHYS_UPDATE;
>    m2p_updates[2].val = cn_pfn;
>    m2p_updates[3].ptr =
> -    page2offset (new_mfn_list[st_pfn]) | MMU_MACHPHYS_UPDATE;
> +    page2offset (virt_mfn_list[st_pfn]) | MMU_MACHPHYS_UPDATE;
>    m2p_updates[3].val = st_pfn;
>
>    grub_xen_mmu_update (m2p_updates, 4, NULL, DOMID_SELF);
> @@ -209,34 +211,43 @@ set_mfns (grub_xen_mfn_t * new_mfn_list, grub_xen_mfn_t 
> pfn)
>  }
>
>  static grub_err_t
> +grub_xen_p2m_alloc (void)
> +{
> +  grub_relocator_chunk_t ch;
> +  grub_size_t p2msize;
> +  grub_err_t err;
> +
> +  state.mfn_list = max_addr;
> +  next_start.mfn_list = max_addr + xen_inf.virt_base;
> +  p2msize = sizeof (grub_xen_mfn_t) * grub_xen_start_page_addr->nr_pages;
> +  err = grub_relocator_alloc_chunk_addr (relocator, &ch, max_addr, p2msize);

Hmmm.... Where relocator is defined?

> +  if (err)
> +    return err;
> +  virt_mfn_list = get_virtual_current_address (ch);
> +  grub_memcpy (virt_mfn_list,
> +            (void *) grub_xen_start_page_addr->mfn_list, p2msize);
> +  max_addr = ALIGN_UP (max_addr + p2msize, PAGE_SIZE);
> +
> +  return GRUB_ERR_NONE;
> +}
> +
> +static grub_err_t
>  grub_xen_boot (void)
>  {
> -  struct grub_relocator_xen_state state;
>    grub_relocator_chunk_t ch;
>    grub_err_t err;
> -  grub_size_t pgtsize;
>    struct start_info *nst;
>    grub_uint64_t nr_info_pages;
>    grub_uint64_t nr_pages, nr_pt_pages, nr_need_pages;
>    struct gnttab_set_version gnttab_setver;
> -  grub_xen_mfn_t *new_mfn_list;
>    grub_size_t i;
>
>    if (grub_xen_n_allocated_shared_pages)
>      return grub_error (GRUB_ERR_BUG, "active grants");
>
> -  state.mfn_list = max_addr;
> -  next_start.mfn_list = max_addr + xen_inf.virt_base;
> -  next_start.first_p2m_pfn = max_addr >> PAGE_SHIFT; /* Is this right? */
> -  pgtsize = sizeof (grub_xen_mfn_t) * grub_xen_start_page_addr->nr_pages;
> -  err = grub_relocator_alloc_chunk_addr (relocator, &ch, max_addr, pgtsize);
> -  next_start.nr_p2m_frames = (pgtsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +  err = grub_xen_p2m_alloc ();
>    if (err)
>      return err;
> -  new_mfn_list = get_virtual_current_address (ch);
> -  grub_memcpy (new_mfn_list,
> -            (void *) grub_xen_start_page_addr->mfn_list, pgtsize);
> -  max_addr = ALIGN_UP (max_addr + pgtsize, PAGE_SIZE);
>
>    err = grub_relocator_alloc_chunk_addr (relocator, &ch,

Ditto. I think that this could be passed as a grub_xen_boot() argument.
Otherwise this appear from nowhere and reading/understanding is more
difficult.

Daniel

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