Messages in this thread | | | Date | Wed, 25 May 2022 09:30:55 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH -next v4 3/7] arm64: add support for machine check error safe |
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On Thu, May 19, 2022 at 02:29:54PM +0800, Tong Tiangen wrote: > > > 在 2022/5/13 23:26, Mark Rutland 写道: > > On Wed, Apr 20, 2022 at 03:04:14AM +0000, Tong Tiangen wrote: > > > During the processing of arm64 kernel hardware memory errors(do_sea()), if > > > the errors is consumed in the kernel, the current processing is panic. > > > However, it is not optimal. > > > > > > Take uaccess for example, if the uaccess operation fails due to memory > > > error, only the user process will be affected, kill the user process > > > and isolate the user page with hardware memory errors is a better choice. > > > > Conceptually, I'm fine with the idea of constraining what we do for a > > true uaccess, but I don't like the implementation of this at all, and I > > think we first need to clean up the arm64 extable usage to clearly > > distinguish a uaccess from another access. > > OK,using EX_TYPE_UACCESS and this extable type could be recover, this is > more reasonable.
Great.
> For EX_TYPE_UACCESS_ERR_ZERO, today we use it for kernel accesses in a > couple of cases, such as > get_user/futex/__user_cache_maint()/__user_swpX_asm(),
Those are all user accesses.
However, __get_kernel_nofault() and __put_kernel_nofault() use EX_TYPE_UACCESS_ERR_ZERO by way of __{get,put}_mem_asm(), so we'd need to refactor that code to split the user/kernel cases higher up the callchain.
> your suggestion is: > get_user continues to use EX_TYPE_UACCESS_ERR_ZERO and the other cases use > new type EX_TYPE_FIXUP_ERR_ZERO?
Yes, that's the rough shape. We could make the latter EX_TYPE_KACCESS_ERR_ZERO to be clearly analogous to EX_TYPE_UACCESS_ERR_ZERO, and with that I susepct we could remove EX_TYPE_FIXUP.
Thanks, Mark.
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