On 9/20/19 8:51 AM, Qiujun Huang wrote:
> __get_user_pages_fast try to walk the page table but the
> hugepage pte is replace by hwpoison swap entry by mca path.
I expect you mean MCE (machine check exception), rather than mca?
> ...
> [15798.177437] mce: Uncorrected hardware memory error in
> user-access at 224f1761c0
> [15798.180171] MCE 0x224f176: Killing pal_main:6784 due to
> hardware memory corruption
> [15798.180176] MCE 0x224f176: Killing qemu-system-x86:167336
> due to hardware memory corruption
> ...
> [15798.180206] BUG: unable to handle kernel
> [15798.180226] paging request at ffff891200003000
> [15798.180236] IP: [<ffffffff8106edae>] gup_pud_range+
> 0x13e/0x1e0
> ...
>
> We need to skip the hwpoison entry in gup_pud_range.
It would be nice if this spelled out a little more clearly what's
wrong. I think you and Aneesh are saying that the entry is really
a swap entry, created by the MCE response to a bad page?
>
> Signed-off-by: Qiujun Huang <hqjagain@xxxxxxxxx>
> ---
> mm/gup.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index 98f13ab..6157ed9 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2230,6 +2230,8 @@ static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
> next = pud_addr_end(addr, end);
> if (pud_none(pud))
> return 0;
> + if (unlikely(!pud_present(pud)))
> + return 0;
If the MCE hwpoison behavior puts in swap entries, then it seems like all
page table walkers would need to check for p*d_present(), and maybe at all
levels too, right?
thanks,
--
John Hubbard
NVIDIA
> if (unlikely(pud_huge(pud))) {
> if (!gup_huge_pud(pud, pudp, addr, next, flags,
> pages, nr))
>
