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

[Juergen Gross <jgross@xxxxxxxx>]

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).

Juergen


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