On 6/8/22 07:43, HORIGUCHI NAOYA(堀口 直也) wrote:
On Tue, Jun 07, 2022 at 02:59:59PM -0700, Andrew Morton wrote:
On Tue, 7 Jun 2022 14:36:00 +0200 David Hildenbrand <david@xxxxxxxxxx> wrote:
On 06.06.22 11:15, HORIGUCHI NAOYA(堀口 直也) wrote:
[ 917.864266] <TASK>
[ 917.864961] clear_huge_page+0x147/0x270
[ 917.866236] hugetlb_fault+0x440/0xad0
[ 917.867366] handle_mm_fault+0x270/0x290
[ 917.868532] do_user_addr_fault+0x1c3/0x680
[ 917.869768] exc_page_fault+0x6c/0x160
[ 917.870912] ? asm_exc_page_fault+0x8/0x30
[ 917.872082] asm_exc_page_fault+0x1e/0x30
[ 917.873220] RIP: 0033:0x7f2aeb8ba367
I don't think of a workaround for this now ...
Could you please tell me how to reproduce this issue?
You are familiar with qemu-monitor-command, so the following procedure
should work for you:
- run a process using hugepages on your VM,
- check the guest physical address of the hugepage (page-types.c is helpful for this),
- inject a MCE with virsh qemu-monitor-command on the guest physical address, then
- unpoison the injected physical address.
That's triggered via debugfs / HWPOISON_INJECT, right?
That's a DEBUG_KERNEL option, so I'm not 100% sure if we really want to
cc stable.
Sure, the impact of the bug is limited.
Sure, it's hardly a must-have. But let's also take the patch
complexity&risk into account. This is one dang simple patch.
Or is it. Should these things be happening outside mf_mutex? What the
heck is the role of mf_mutex anyway?
mf_mutex is to ensure that only one error handling thread can handle
the pfn at one time, but set_mce_nospec() is called outside it now.
So if we want to prevent the race with unmap, both of set_mce_nospec()
and the new kpte check might need to be done in mf_mutex.
- Naoya Horiguchi
OK, I'll sent a v2 patch which includes:
- this change gets protected by mf_mutex
- use -EOPNOTSUPP instead of -EPERM
By the way, I assume that the similar trace(provided by Naoya) is not a
same issue. It seems undissolved huge page with corrupted KPTE. I'm
trying to fix it ...
--
zhenwei pi
