linux-kernel - Re: [PATCH v2] powerpc/traps: Enhance readability for trap types

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Date:   Mon, 5 Apr 2021 20:03:25 +0800
From:   Xiongwei Song <sxwjean@...com>
To:     Segher Boessenkool <segher@...nel.crashing.org>
Cc:     Xiongwei Song <sxwjean@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        benh@...nel.crashing.org, paulus@...ba.org, oleg@...hat.com,
        npiggin@...il.com, Christophe Leroy <christophe.leroy@...roup.eu>,
        msuchanek@...e.de, aneesh.kumar@...ux.ibm.com,
        ravi.bangoria@...ux.ibm.com, mikey@...ling.org,
        haren@...ux.ibm.com, alistair@...ple.id.au, jniethe5@...il.com,
        peterz@...radead.org, leobras.c@...il.com,
        akpm@...ux-foundation.org, rppt@...nel.org, peterx@...hat.com,
        atrajeev@...ux.vnet.ibm.com, maddy@...ux.ibm.com,
        kjain@...ux.ibm.com, kan.liang@...ux.intel.com, aik@...abs.ru,
        pmladek@...e.com, john.ogness@...utronix.de,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org
Subject: Re: [PATCH v2] powerpc/traps: Enhance readability for trap types


> On Apr 2, 2021, at 12:11 AM, Segher Boessenkool <segher@...nel.crashing.org> wrote:
> 
> On Thu, Apr 01, 2021 at 10:55:58AM +0800, Xiongwei Song wrote:
>> Segher Boessenkool <segher@...nel.crashing.org> 于2021年4月1日周四 上午6:15写道：
>> 
>>> On Wed, Mar 31, 2021 at 08:58:17PM +1100, Michael Ellerman wrote:
>>>> So perhaps:
>>>> 
>>>>  EXC_SYSTEM_RESET
>>>>  EXC_MACHINE_CHECK
>>>>  EXC_DATA_STORAGE
>>>>  EXC_DATA_SEGMENT
>>>>  EXC_INST_STORAGE
>>>>  EXC_INST_SEGMENT
>>>>  EXC_EXTERNAL_INTERRUPT
>>>>  EXC_ALIGNMENT
>>>>  EXC_PROGRAM_CHECK
>>>>  EXC_FP_UNAVAILABLE
>>>>  EXC_DECREMENTER
>>>>  EXC_HV_DECREMENTER
>>>>  EXC_SYSTEM_CALL
>>>>  EXC_HV_DATA_STORAGE
>>>>  EXC_PERF_MONITOR
>>> 
>>> These are interrupt (vectors), not exceptions.  It doesn't matter all
>>> that much, but confusing things more isn't useful either!  There can be
>>> multiple exceptions that all can trigger the same interrupt.
>>> 
>>> When looking at the reference manual of e500 and e600 from NXP
>> official, they call them as interrupts.While looking at the "The
>> Programming Environments"
>> that is also from NXP, they call them exceptions. Looks like there is
>> no explicit distinction between interrupts and exceptions.
> 
> The architecture documents have always called it interrupts.  The PEM
> says it calls them exceptions instead, but they are called interrupts in
> the architecture (and the PEM says that, too).
> 
>> Here is the "The Programming Environments" link:
>> https://www.nxp.com.cn/docs/en/user-guide/MPCFPE_AD_R1.pdf
> 
> That document is 24 years old.  The architecture is still published,
> new versions regularly.
> 
>> As far as I know, the values of interrupts or exceptions above are defined
>> explicitly in reference manual or the programming environments.
> 
> They are defined in the architecture.
> 
>> Could
>> you please provide more details about multiple exceptions with the same
>> interrupts?
> 
> The simplest example is 700, program interrupt.  There are many causes
> for it, including all the exceptions in FPSCR: VX, ZX, OX, UX, XX, and
> VX is actually divided into nine separate cases itself.  There also are
> the various causes of privileged instruction type program interrupts,
> and  the trap type program interrupt, but the FEX ones are most obvious
> here.

Thanks for the explanation.

Regards,
Xiongwei

> 
> 
> Segher