Messages in this thread | | | Date | Thu, 5 May 2022 22:33:41 +0800 | Subject | Re: [PATCH -next v4 4/7] arm64: add copy_{to, from}_user to machine check safe | From | Tong Tiangen <> |
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在 2022/5/5 21:41, Catalin Marinas 写道: > On Thu, May 05, 2022 at 02:39:43PM +0800, Tong Tiangen wrote: >> 在 2022/5/4 18:26, Catalin Marinas 写道: >>> On Wed, Apr 20, 2022 at 03:04:15AM +0000, Tong Tiangen wrote: >>>> Add copy_{to, from}_user() to machine check safe. >>>> >>>> If copy fail due to hardware memory error, only the relevant processes are >>>> affected, so killing the user process and isolate the user page with >>>> hardware memory errors is a more reasonable choice than kernel panic. >>> >>> Just to make sure I understand - we can only recover if the fault is in >>> a user page. That is, for a copy_from_user(), we can only handle the >>> faults in the source address, not the destination. >> >> At the beginning, I also thought we can only recover if the fault is in a >> user page. >> After discussion with a Mark[1], I think no matter user page or kernel page, >> as long as it is triggered by the user process, only related processes will >> be affected. According to this >> understanding, it seems that all uaccess can be recovered. >> >> [1]https://patchwork.kernel.org/project/linux-arm-kernel/patch/20220406091311.3354723-6-tongtiangen@huawei.com/ > > We can indeed safely skip this copy and return an error just like > pretending there was a user page fault. However, my point was more > around the "isolate the user page with hardware memory errors". If the > fault is on a kernel address, there's not much you can do about. You'll > likely trigger it later when you try to access that address (maybe it > was freed and re-allocated). Do we hope we won't get the same error > again on that kernel address?
I think the page with memory error will be isolated by memory_failure(), generally, isolation will succeed, if isolate failure(we need to find out why), then maybe the same error will trigger it later.
Thanks.
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