On Tue, Apr 25, 2017 at 11:53 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> * Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
>> On Tue, Apr 25, 2017 at 2:25 AM, Kirill A. Shutemov
>> <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
>> > remove_pagetable() does page walk using p*d_page_vaddr() plus cast.
>> > It's not canonical approach -- we usually use p*d_offset() for that.
>> >
>> > It works fine as long as all page table levels are present. We broke the
>> > invariant by introducing folded p4d page table level.
>> >
>> > As result, remove_pagetable() interprets PMD as PUD and it leads to
>> > crash:
>> >
>> > BUG: unable to handle kernel paging request at ffff880300000000
>> > IP: memchr_inv+0x60/0x110
>> > PGD 317d067
>> > P4D 317d067
>> > PUD 3180067
>> > PMD 33f102067
>> > PTE 8000000300000060
>> >
>> > Let's fix this by using p*d_offset() instead of p*d_page_vaddr() for
>> > page walk.
>> >
>> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
>> > Reported-by: Dan Williams <dan.j.williams@xxxxxxxxx>
>> > Fixes: f2a6a7050109 ("x86: Convert the rest of the code to support p4d_t")
>>
>> Thanks! This patch on top of tip/master passes a full run of the
>> nvdimm regression suite.
>>
>> Tested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> Does a re-application of:
>
> "x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation"
>
> still work (which you can achive via 'git revert 6dd29b3df975'), or is that
> another breakage?
That's another breakage. We're discussing how to resolve it in this thread:
http://www.spinics.net/lists/linux-mm/msg126056.html
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
