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 18:14, Daniel Kiper wrote:
> On Thu, Feb 11, 2016 at 01:53:51PM +0100, 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).
> 
> It seems that memory is freed by higher level functions when you
> try to use the same loader or other one. Otherwise it would be clear
> memory leak. Could you double check it?

Yes, you are right. Other loaders are calling grub_relocator_unload() to
achieve this before allocating a new relocator or when unloading the
module.


Juergen


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