Messages in this thread | | | Date | Fri, 27 May 2022 09:40:36 +0800 | Subject | Re: [PATCH -next v4 3/7] arm64: add support for machine check error safe | From | Tong Tiangen <> |
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在 2022/5/26 17:50, Mark Rutland 写道: > On Thu, May 26, 2022 at 11:36:41AM +0800, Tong Tiangen wrote: >> >> >> 在 2022/5/25 16:30, Mark Rutland 写道: >>> 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. >> According to your suggestion, i think the definition is like this: >> >> #define EX_TYPE_NONE 0 >> #define EX_TYPE_FIXUP 1 --> delete >> #define EX_TYPE_BPF 2 >> #define EX_TYPE_UACCESS_ERR_ZERO 3 >> #define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 >> #define EX_TYPE_UACCESS xx --> add >> #define EX_TYPE_KACCESS_ERR_ZERO xx --> add >> [The value defined by the macro here is temporary] > > Almost; you don't need to add EX_TYPE_UACCESS here, as you can use > EX_TYPE_UACCESS_ERR_ZERO for that. > > We already have: > > | #define _ASM_EXTABLE_UACCESS_ERR(insn, fixup, err) \ > | _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, wzr) > > ... and we can add: > > | #define _ASM_EXTABLE_UACCESS(insn, fixup) \ > | _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, wzr, wzr) > > > ... and maybe we should use 'xzr' rather than 'wzr' for clarity. > >> There are two points to modify: >> >> 1、_get_kernel_nofault() and __put_kernel_nofault() using >> EX_TYPE_KACCESS_ERR_ZERO, Other positions using EX_TYPE_UACCESS_ERR_ZERO >> keep unchanged. > > That sounds right to me. This will require refactoring __raw_{get,put}_mem() > and __{get,put}_mem_asm(). > >> 2、delete EX_TYPE_FIXUP. >> >> There is no doubt about others. As for EX_TYPE_FIXUP, I think it needs to be >> retained, _cond_extable(EX_TYPE_FIXUP) is still in use in assembler.h. > > We use _cond_extable for cache maintenance uaccesses, so those should be moved > over to to EX_TYPE_UACCESS_ERR_ZERO. We can rename _cond_extable to > _cond_uaccess_extable for clarity. > > That will require restructuring asm-extable.h a bit. If that turns out to be > painful I'm happy to take a look. > > Thanks, > Mark.
OK, I'll do it these days, thanks a lot.
> .
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