[Crash-utility] [PATCH v3 0/3] vmalloc translation support for PPC

[Suzuki K. Poulose]

On 02/17/2012 12:43 AM, Dave Anderson wrote:
>
>
> ----- Original Message -----
>> On 02/16/2012 09:52 PM, Dave Anderson wrote:
>>>
>>>
>>> ----- Original Message -----
>>> ...
>>>>> So just do the same thing -- no verbose expanation is required.
>>>>
>>>> There are two ways to fix this :
>>>>
>>>> 1) Fix dump_mem_map*() to print the header only when there is
>>>> information to dump.
>>>>
>>>> --- a/memory.c
>>>> +++ b/memory.c
>>>> @@ -4637,13 +4637,6 @@ dump_mem_map_SPARSEMEM(struct meminfo *mi)
>>>>                            continue;
>>>>                    }
>>>>
>>>> -               if (print_hdr) {
>>>> -                       if (!(pc->curcmd_flags&   HEADER_PRINTED))
>>>> -                               fprintf(fp, "%s", hdr);
>>>> -                       print_hdr = FALSE;
>>>> -                       pc->curcmd_flags |= HEADER_PRINTED;
>>>> -               }
>>>> -
>>>>                    pp = section_mem_map_addr(section);
>>>>                    pp = sparse_decode_mem_map(pp, section_nr);
>>>>                    phys = (physaddr_t) section_nr *
>>>>                    PAGES_PER_SECTION()
>>>>                    * PAGESIZE();
>>>> @@ -4854,6 +4847,13 @@ dump_mem_map_SPARSEMEM(struct meminfo *mi)
>>>>                            }
>>>>
>>>>                            if (bufferindex>   buffersize) {
>>>> +                               if (print_hdr) {
>>>> +                                       if (!(pc->curcmd_flags&
>>>>   HEADER_PRINTED))
>>>> +                                               fprintf(fp, "%s",
>>>> hdr);
>>>> +                                       print_hdr = FALSE;
>>>> +                                       pc->curcmd_flags |=
>>>> HEADER_PRINTED;
>>>> +                               }
>>>> +
>>>>                                    fprintf(fp, "%s", outputbuffer);
>>>>                                    bufferindex = 0;
>>>>                            }
>>>> @@ -4867,6 +4867,13 @@ dump_mem_map_SPARSEMEM(struct meminfo *mi)
>>>>            }
>>>>
>>>>            if (bufferindex>   0) {
>>>> +               if (print_hdr) {
>>>> +                       if (!(pc->curcmd_flags&   HEADER_PRINTED))
>>>> +                               fprintf(fp, "%s", hdr);
>>>> +                       print_hdr = FALSE;
>>>> +                       pc->curcmd_flags |= HEADER_PRINTED;
>>>> +               }
>>>> +
>>>>                    fprintf(fp, "%s", outputbuffer);
>>>>            }
>>>>
>>>> Similarly for the dump_mem_map().
>>>>
>>>> 2) Fix ppc_pgd_vtop() to return FALSE if the paddr>
>>>>   machdep->memsize
>>>>
>>>> --- a/ppc.c
>>>> +++ b/ppc.c
>>>> @@ -438,6 +438,10 @@ ppc_pgd_vtop(ulong *pgd, ulong vaddr,
>>>> physaddr_t
>>>> *paddr, int verbose)
>>>>
>>>>            *paddr = PAGEBASE(pte) + PAGEOFFSET(vaddr);
>>>>
>>>> +       if (*paddr>   machdep->memsize)
>>>> +       /* We don't have pages above System RAM */
>>>> +               return FALSE;
>>>> +
>>>>            return TRUE;
>>>>
>>>>     no_page:
>>>>
>>>> I prefer the (1). What do you think ?
>>>
>>> Hi Suzuki,
>>>
>>> Hmmm -- with respect to (1), I suppose that would work, although
>>> given that both x86 and x86_64 pass through dump_mem_map_SPARSEMEM()
>>> without printing the header in a non-existent-page case, I don't
>>> understand why ppc is different?
>> Yep, I digged into that a little, but not deep enough to debug it with
>> a dump. Nothing was evident from the code :(.
>
> Right -- I tried debugging it from the x86 and x86_64 perspective,
> and couldn't see why ppc would be different!  ;-)
Ah, well, I was talking about the x86_64 dump.
I could explain the PPC side of affairs :-). We have page the following
flags set for the page(with the  actual PPC44x page flags support) :

VIRTUAL   PHYSICAL
d1002000  20ec00000

PAGE DIRECTORY: c0578000
   PGD: c0579a20 => c784b000
   PMD: c784b000 => c784b010
   PTE: c784b010 => 20ec0051b
  PAGE: 20ec00000

    PTE     PHYSICAL   FLAGS
20ec0051b  20ec00000  (PRESENT|RW|GUARDED|NO_CACHE|DIRTY|ACCESSED)


So the page is 'present', but there is no page descriptor associated with it.
Hence dump_mem_map() would still be called and hence the problem.

Why doesn't it get called in x86_64 case even when the flags indicate page 'PRESENT' ?

Cheers
Suzuki