Hi guys, On 17/09/2020 09:40, Borislav Petkov wrote: > On Thu, Sep 10, 2020 at 03:29:56PM +0000, Shiju Jose wrote: > You can't know what exactly you wanna do if you don't have a use case > you're trying to address. > >> According to the ARM Processor CPER definition the error types >> reported are Cache Error, TLB Error, Bus Error and micro-architectural >> Error. > > Bus error sounds like not even originating in the CPU but the CPU only > reporting it. Imagine if that really were the case, and you go disable > the CPU but the error source is still there. You've just disabled the > reporting of the error only and now you don't even know anymore that > you're getting errors. > >> Few thoughts on this, >> 1. Not sure will a CPU core would work/perform as normal after disabling >> a functional unit? > > You can disable parts of caches, etc, so that you can have a somewhat > functioning CPU until the replacement maintenance can take place. This is implementation-specific stuff that only firmware can do... >> 2. Support in the HW to disable a function unit alone may not available. > > Yes. > >> 3. If it is require to store and retrieve the error count based on >> functional unit, then CEC will become more complex? > > Depends on how it is designed. That's why we're first talking about what > needs to be done exactly before going off and doing something. > >> This requirement is the part of the early fault prediction by taking >> action when large number of corrected errors reported on a CPU core >> before it causing serious faults. > > And do you know of actual real-life examples where this is really the > case? Do you have any users who report a large error count on ARM CPUs, > originating from the caches and that something like that would really > help? > > Because from my x86 CPUs limited experience, the cache arrays are mostly > fine and errors reported there are not something that happens very > frequently so we don't even need to collect and count those. > > So is this something which you need to have in order to check a box > somewhere that there is some functionality or is there an actual > real-life use case behind it which a customer has requested? If the corrected-count is available somewhere, can't this policy be made in user-space? Thanks, James
