Messages in this thread | | | Date | Sat, 7 May 2022 08:28:05 +0800 | Subject | Re: Re: [PATCH 3/4] mm/memofy-failure.c: optimize hwpoison_filter | From | zhenwei pi <> |
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On 5/7/22 00:28, David Hildenbrand wrote: > On 06.05.22 15:38, zhenwei pi wrote: >> >> >> On 5/6/22 16:59, Naoya Horiguchi wrote: >>> On Fri, Apr 29, 2022 at 10:22:05PM +0800, zhenwei pi wrote: >>>> In the memory failure procedure, hwpoison_filter has higher priority, >>>> if memory_filter() filters the error event, there is no need to do >>>> the further work. >>> >>> Could you clarify what problem you are trying to solve (what does >>> "optimize" mean in this context or what is the benefit)? >>> >> >> OK. The background of this work: >> As well known, the memory failure mechanism handles memory corrupted >> event, and try to send SIGBUS to the user process which uses this >> corrupted page. >> >> For the virtualization case, QEMU catches SIGBUS and tries to inject MCE >> into the guest, and the guest handles memory failure again. Thus the >> guest gets the minimal effect from hardware memory corruption. >> >> The further step I'm working on: >> 1, try to modify code to decrease poisoned pages in a single place >> (mm/memofy-failure.c: simplify num_poisoned_pages_dec in this series). >> >> 2, try to use page_handle_poison() to handle SetPageHWPoison() and >> num_poisoned_pages_inc() together. It would be best to call >> num_poisoned_pages_inc() in a single place too. I'm not sure if this is >> possible or not, please correct me if I misunderstand. >> >> 3, introduce memory failure notifier list in memory-failure.c: notify >> the corrupted PFN to someone who registers this list. >> If I can complete [1] and [2] part, [3] will be quite easy(just call >> notifier list after increasing poisoned page). >> >> 4, introduce memory recover VQ for memory balloon device, and registers >> memory failure notifier list. During the guest kernel handles memory >> failure, balloon device gets notified by memory failure notifier list, >> and tells the host to recover the corrupted PFN(GPA) by the new VQ. > > Most probably you might want to do that asynchronously, and once the > callback succeeds, un-poison the page. > Yes!
>> >> 5, host side remaps the corrupted page(HVA), and tells the guest side to >> unpoison the PFN(GPA). Then the guest fixes the corrupted page(GPA) >> dynamically. > > I think QEMU already does that during reboots. Now it would be triggered > by the guest for individual pages. > Yes, currently QEMU supports to un-poison corrupted pages during reset/reboot. We can reuse some code to do the work in this case, this allows a VM to fix corrupted pages as soon as possible(also no need to reset/reboot).
>> >> Because [4] and [5] are related to balloon device, also CC Michael, >> David and Jason. > > Doesn't sound too crazy for me, although it's a shame that we always > have to use virtio-balloon for such fairly balloon-unrelated things. > Thanks!
-- zhenwei pi
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