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

[Dave Anderson]

----- Original Message -----
> 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' ?

I don't know -- that's what I was asking!  But I'd like to prevent it
in all cases with the patch to do_vtop().

Dave