Re: [Xen-devel] [PATCH v2 3/6] xen: factor out allocation of page tables into separate function

[Vladimir 'Ï-coder/phcoder' Serbinenko <phcoder@xxxxxxxxx>]

On 11.02.2016 13:53, Juergen Gross wrote:
> On 11/02/16 13:27, Daniel Kiper wrote:
>> On Thu, Feb 11, 2016 at 08:53:23AM +0100, Juergen Gross wrote:
>>> Do the allocation of page tables in a separate function. This will
>>> allow to do the allocation at different times of the boot preparations
>>> depending on the features the kernel is supporting.
>>>
>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>> ---
>>>  grub-core/loader/i386/xen.c | 82 
>>> ++++++++++++++++++++++++++++-----------------
>>>  1 file changed, 51 insertions(+), 31 deletions(-)
>>>
>>> diff --git a/grub-core/loader/i386/xen.c b/grub-core/loader/i386/xen.c
>>> index e48cc3f..65cec27 100644
>>> --- a/grub-core/loader/i386/xen.c
>>> +++ b/grub-core/loader/i386/xen.c
>>> @@ -56,6 +56,9 @@ static struct grub_relocator_xen_state state;
>>>  static grub_xen_mfn_t *virt_mfn_list;
>>>  static struct start_info *virt_start_info;
>>>  static grub_xen_mfn_t console_pfn;
>>> +static grub_uint64_t *virt_pgtable;
>>> +static grub_uint64_t pgtbl_start;
>>> +static grub_uint64_t pgtbl_end;
>>
>> Same as in patches #1 and #2.
> 
> Yep.
> 
>>
>>>  #define PAGE_SIZE 4096
>>>  #define MAX_MODULES (PAGE_SIZE / sizeof (struct xen_multiboot_mod_list))
>>> @@ -106,17 +109,17 @@ get_pgtable_size (grub_uint64_t total_pages, 
>>> grub_uint64_t virt_base)
>>>
>>>  static void
>>>  generate_page_table (grub_uint64_t *where, grub_uint64_t paging_start,
>>> -                grub_uint64_t total_pages, grub_uint64_t virt_base,
>>> -                grub_xen_mfn_t *mfn_list)
>>> +                grub_uint64_t paging_end, grub_uint64_t total_pages,
>>> +                grub_uint64_t virt_base, grub_xen_mfn_t *mfn_list)
>>>  {
>>>    if (!virt_base)
>>> -    total_pages++;
>>> +    paging_end++;
>>>
>>>    grub_uint64_t lx[NUMBER_OF_LEVELS], lxs[NUMBER_OF_LEVELS];
>>>    grub_uint64_t nlx, nls, sz = 0;
>>>    int l;
>>>
>>> -  nlx = total_pages;
>>> +  nlx = paging_end;
>>>    nls = virt_base >> PAGE_SHIFT;
>>>    for (l = 0; l < NUMBER_OF_LEVELS; l++)
>>>      {
>>> @@ -160,7 +163,7 @@ generate_page_table (grub_uint64_t *where, 
>>> grub_uint64_t paging_start,
>>>    if (pr)
>>>      pg += POINTERS_PER_PAGE;
>>>
>>> -  for (j = 0; j < total_pages; j++)
>>> +  for (j = 0; j < paging_end; j++)
>>>      {
>>>        if (j >= paging_start && j < lp)
>>>     pg[j + lxs[0]] = page2offset (mfn_list[j]) | 5;
>>> @@ -261,24 +264,12 @@ grub_xen_special_alloc (void)
>>>  }
>>>
>>>  static grub_err_t
>>> -grub_xen_boot (void)
>>> +grub_xen_pt_alloc (void)
>>>  {
>>>    grub_relocator_chunk_t ch;
>>>    grub_err_t err;
>>>    grub_uint64_t nr_info_pages;
>>>    grub_uint64_t nr_pages, nr_pt_pages, nr_need_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");
>>> -
>>> -  err = grub_xen_p2m_alloc ();
>>> -  if (err)
>>> -    return err;
>>> -  err = grub_xen_special_alloc ();
>>> -  if (err)
>>> -    return err;
>>>
>>>    next_start.pt_base = max_addr + xen_inf.virt_base;
>>>    state.paging_start = max_addr >> PAGE_SHIFT;
>>> @@ -298,30 +289,59 @@ grub_xen_boot (void)
>>>        nr_pages = nr_need_pages;
>>>      }
>>>
>>> -  grub_dprintf ("xen", "bootstrap domain %llx+%llx\n",
>>> -           (unsigned long long) xen_inf.virt_base,
>>> -           (unsigned long long) page2offset (nr_pages));
>>> -
>>>    err = grub_relocator_alloc_chunk_addr (relocator, &ch,
>>>                                      max_addr, page2offset (nr_pt_pages));
>>>    if (err)
>>>      return err;
>>>
>>> +  virt_pgtable = get_virtual_current_address (ch);
>>> +  pgtbl_start = max_addr >> PAGE_SHIFT;
>>> +  max_addr += page2offset (nr_pt_pages);
>>> +  state.stack = max_addr + STACK_SIZE + xen_inf.virt_base;
>>> +  state.paging_size = nr_pt_pages;
>>> +  next_start.nr_pt_frames = nr_pt_pages;
>>> +  max_addr = page2offset (nr_pages);
>>> +  pgtbl_end = nr_pages;
>>> +
>>> +  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");
>>> +
>>> +  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;
>>
>> Should not we free memory allocated by grub_xen_p2m_alloc() and
>> grub_xen_special_alloc() if grub_xen_pt_alloc() failed?
> 
> Hmm, why? If I don't miss anything freeing memory in case of error isn't
> done anywhere (at least not in this source file).
> 
If we don't it's a bug and not an excuse to continue doing bad things
> Juergen
> 
> .
>

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