From: santosh.shilimkar@ti•com (Santosh Shilimkar)
To: linux-arm-kernel@lists•infradead.org
Subject: Multi-platform, and secure-only ARM errata workarounds
Date: Wed, 27 Feb 2013 11:37:08 +0530 [thread overview]
Message-ID: <512DA28C.1080909@ti.com> (raw)
In-Reply-To: <20130226184942.GV17833@n2100.arm.linux.org.uk>
On Wednesday 27 February 2013 12:19 AM, Russell King - ARM Linux wrote:
> On Tue, Feb 26, 2013 at 11:30:08AM -0700, Stephen Warren wrote:
>> On 02/26/2013 11:11 AM, Russell King - ARM Linux wrote:
>>> On Tue, Feb 26, 2013 at 11:01:30AM -0700, Stephen Warren wrote:
>>>> The conditional in that statement makes me wonder which of the following
>>>> operations will fault in non-secure mode:
>>>>
>>>> 1) Reading from the diagnostic register.
>>>
>>> Won't fault.
>>>
>>>> 2) Writing to the diagnostic register, of a value the same as what's
>>>> already there.
>>>
>>> Will fault.
>>>
>>>> 3) Writing to the diagnostic register, of a value different than what's
>>>> already there.
>>>
>>> Will fault.
>>>
>>>> Would the following not fault in both secure and non-secure mode:
>>>>
>>>> read diagnostic register
>>>> if desired bit already set:
>>>> b 1f
>>>> set desired bit
>>>> write value back to diagnostic register
>>>> 1:
>>>
>>> That is exactly what we do
>>
>> Well, I asked because for the 3 WARs in question at least, that isn't
>> what the code does. For example, from proc-v7.s:
>>
>> #ifdef CONFIG_ARM_ERRATA_742230
>> cmp r6, #0x22 @ only present up to r2p2
>> mrcle p15, 0, r10, c15, c0, 1 @ read diagnostic register
>> orrle r10, r10, #1 << 4 @ set bit #4
>> mcrle p15, 0, r10, c15, c0, 1 @ write diagnostic register
>> #endif
>>
>> (unless that orrle affects the flags and hence skips the mcrle, but I
>> don't think so.)
>
> Hmm. I've not really been taking much notice of how these work-arounds
> all work - maybe it's safe to write this diagnostic register from
> non-secure mode then?
>
> I have noticed this kind of fishy thing with OMAP4430 running in non-secure
> mode - some registers I thought would cause an exception don't. No idea
> why not...
>
They do fault on OMAP. We discussed the issue in the past [1] [2].
The only way we could get around is to disable those WA flags in config.
I was told to move such requirements to boot-loaders then
Regards,
Santosh
[1] https://patchwork.kernel.org/patch/1743211/
[2] https://lkml.org/lkml/2012/12/10/321
next prev parent reply other threads:[~2013-02-27 6:07 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-25 23:47 Multi-platform, and secure-only ARM errata workarounds Stephen Warren
2013-02-26 9:36 ` Marc Dietrich
2013-02-26 16:39 ` Stephen Warren
2013-02-26 22:31 ` Nicolas Pitre
2013-02-27 9:03 ` Marc Dietrich
2013-02-27 14:00 ` Rob Herring
2013-02-27 17:42 ` Stephen Warren
2013-02-28 13:58 ` Marc Dietrich
2013-02-26 10:23 ` Arnd Bergmann
2013-02-26 10:31 ` Catalin Marinas
2013-02-26 10:35 ` Catalin Marinas
2013-02-26 10:48 ` Arnd Bergmann
2013-02-26 11:11 ` Catalin Marinas
2013-02-26 11:35 ` Russell King - ARM Linux
2013-02-26 14:07 ` Rob Herring
2013-02-26 18:01 ` Stephen Warren
2013-02-26 18:11 ` Russell King - ARM Linux
2013-02-26 18:30 ` Stephen Warren
2013-02-26 18:49 ` Russell King - ARM Linux
2013-02-27 6:07 ` Santosh Shilimkar [this message]
2013-03-01 17:37 ` Stephen Warren
2013-03-01 18:05 ` Russell King - ARM Linux
2013-03-04 6:34 ` Peter De Schrijver
2013-03-04 9:16 ` Peter De Schrijver
2013-03-04 17:08 ` Stephen Warren
2013-03-05 7:40 ` Peter De Schrijver
2013-03-05 17:00 ` Stephen Warren
2013-03-06 8:14 ` Peter De Schrijver
2013-03-06 16:18 ` Stephen Warren
2013-03-10 17:25 ` Santosh Shilimkar
2013-03-10 18:47 ` Olof Johansson
2013-03-11 16:59 ` Stephen Warren
2013-03-11 18:54 ` Jason Gunthorpe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=512DA28C.1080909@ti.com \
--to=santosh.shilimkar@ti$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox