From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: andre.przywara@arm.com, wei.chen@linaro.org, wei.liu2@citrix.com,
steve.capper@arm.com, xen-devel@lists.xen.org
Subject: Re: [PATCH v2 15/15] xen/arm: arm64: Document Cortex-A57 erratum 834220
Date: Tue, 31 May 2016 11:39:32 +0100 [thread overview]
Message-ID: <574D69E4.40306@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1605311029040.3896@sstabellini-ThinkPad-X260>
Hi Stefano,
On 31/05/16 10:34, Stefano Stabellini wrote:
> On Mon, 30 May 2016, Julien Grall wrote:
>> On 30/05/2016 17:19, Stefano Stabellini wrote:
>>>> "Erratum #834220: Xen needs to check that the Stage 1 translation does not
>>>> generate a fault before handling Stage 2 fault. If it is a stage 1
>>>> translation
>>>> fault, return to the guest to let the project injecting the correct fault.
>>>>
>>>> XXX: This can be optimized to avoid some unnecessary translation."
>>>
>>> What about adding a lengthy and detailed description of the erratum
>>> elsewhere and just having a one liner at the call sites, such as:
>>
>> I don't see any problem to have "lengthy" comment twice. It could actually be
>> 3 lines because the last one is a TODO.
>
> In my experience comments tend to be modified and when it happens, not
> all the instances get always updated. That's why I would prefer to have
> only one good explanation somewhere and then references to it.
>
> That said, they are just comments, even if they don't get properly
> updated the code won't break because of that (not immediately at least).
> So I am not going to be headstrong on this.
>
>
>> I thought about merging some bits of do_trap_instr_abort_guest and
>> do_trap_data_abort_guest, but at first glance it is not that simple.
>>
>>> /* Erratum #834220: check Stage1 translation does not generate faults first!
>>> */
>>>
>>> so that developers can easily grep for #834220 through the code to have
>>> the full explanation?
>>
>> Where would you put the full explanation? do_trap_hypervisor does not make
>> sense because it does not deal with the erratum. When we will come back in few
>> months time, we will wonder why the comment is there.
>
> docs/misc/arm/silicon-errata.txt?
> do_trap_instr_abort_guest or do_trap_data_abort_guest but not both (only
> a reference in the other?
silicon-errata.txt could be a good place.
Cheers,
--
Julien Grall
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prev parent reply other threads:[~2016-05-31 10:39 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-23 14:17 [PATCH v2 00/15] xen/arm: Introduce alternative runtime patching for ARM64 Julien Grall
2016-05-23 14:17 ` [PATCH v2 01/15] xen/arm: Makefile: Sort the entries alphabetically Julien Grall
2016-05-23 14:17 ` [PATCH v2 02/15] xen/arm: Include the header asm-arm/system.h in asm-arm/page.h Julien Grall
2016-05-23 14:17 ` [PATCH v2 03/15] xen/arm: Add macros to handle the MIDR Julien Grall
2016-05-23 14:17 ` [PATCH v2 04/15] xen/arm: Add cpu_hwcap bitmap Julien Grall
2016-05-30 14:19 ` Stefano Stabellini
2016-05-23 14:17 ` [PATCH v2 05/15] xen/arm64: Add an helper to invalidate all instruction caches Julien Grall
2016-05-23 14:17 ` [PATCH v2 06/15] xen/arm: arm64: Move the define BRK_BUG_FRAME into a separate header Julien Grall
2016-05-23 14:17 ` [PATCH v2 07/15] xen/arm: arm64: Reserve a brk immediate to fault on purpose Julien Grall
2016-05-23 14:17 ` [PATCH v2 08/15] xen/arm: arm64: Add helpers to decode and encode branch instructions Julien Grall
2016-05-30 14:29 ` Stefano Stabellini
2016-05-23 14:17 ` [PATCH v2 09/15] xen/arm: Introduce alternative runtime patching Julien Grall
2016-05-23 14:17 ` [PATCH v2 10/15] xen/arm: Detect silicon revision and set cap bits accordingly Julien Grall
2016-05-30 15:02 ` Stefano Stabellini
2016-05-30 16:37 ` Julien Grall
2016-05-31 9:27 ` Stefano Stabellini
2016-05-31 10:36 ` Julien Grall
2016-06-01 9:46 ` Stefano Stabellini
2016-06-01 12:47 ` Julien Grall
2016-06-02 11:43 ` Julien Grall
2016-06-02 11:45 ` Julien Grall
2016-05-23 14:17 ` [PATCH v2 11/15] xen/arm: Document the errata implemented in Xen Julien Grall
2016-05-23 14:38 ` Andrew Cooper
2016-05-24 9:13 ` Julien Grall
2016-05-30 15:08 ` Stefano Stabellini
2016-05-23 14:17 ` [PATCH v2 12/15] xen/arm: arm64: Add Cortex-A53 cache errata workaround Julien Grall
2016-05-24 2:46 ` Chenxiao Zhao
2016-05-24 8:56 ` Julien Grall
2016-05-23 14:17 ` [PATCH v2 13/15] xen/arm: arm64: Add cortex-A57 erratum 832075 workaround Julien Grall
2016-05-23 14:17 ` [PATCH v2 14/15] xen/arm: traps: Don't inject a fault if the translation VA -> IPA fails Julien Grall
2016-05-30 14:50 ` Stefano Stabellini
2016-05-23 14:17 ` [PATCH v2 15/15] xen/arm: arm64: Document Cortex-A57 erratum 834220 Julien Grall
2016-05-30 15:11 ` Stefano Stabellini
2016-05-30 16:15 ` Julien Grall
2016-05-30 16:19 ` Stefano Stabellini
2016-05-30 16:33 ` Julien Grall
2016-05-31 9:34 ` Stefano Stabellini
2016-05-31 10:39 ` Julien Grall [this message]
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