All of lore.kernel.org
 help / color / mirror / Atom feed
From: Julien Grall <julien.grall@linaro.org>
To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: stefano.stabellini@eu.citrix.com, tim@xen.org, xen-devel@lists.xen.org
Subject: Re: [PATCH 5/9] xen: arm: Handle CP15 register traps from userspace
Date: Wed, 10 Sep 2014 11:56:09 -0700	[thread overview]
Message-ID: <54109EC9.1070303@linaro.org> (raw)
In-Reply-To: <1410342483.8217.274.camel@kazak.uk.xensource.com>



On 10/09/14 02:48, Ian Campbell wrote:
> On Tue, 2014-09-09 at 16:42 -0700, Julien Grall wrote:
>> Hi Ian,
>>
>> On 09/09/14 09:23, Ian Campbell wrote:
>>> Previously userspace access to PM* would have been incorrectly (but benignly)
>>> implemented as RAZ/WI when running on a 32-bit kernel and would cause a
>>> hypervisor exception (host crash) when running a 64-bit kernel (this was
>>> already solved via the fix to XSA-102).
>>>
>>> CLIDR, CCSIDR, DCCISW, ACTLR, PMINTENSET, PMINTENCLR are EL1 only, attempts to
>>> access from EL0 will trap to EL1 not to us, hence BUG_ON is appropriate now.
>>
>> In the unlikely case it happens, I don't think it will harm Xen, but
>> only the guest. So is the BUG_ON really necessary on these registers?
>>
>> I think we should use BUG_ON when we know that it will harm the Xen and
>> it's not possible to come back from the state.
>
> AIUI it would be a hardware bug to see these traps in Xen. I think a
> BUG_ON is acceptable for such an occurrence.

I would turn into an ASSERT to avoid checking it in non-debug build.

Regards,

-- 
Julien Grall

  reply	other threads:[~2014-09-10 18:56 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-09 16:22 [RFC PATCH 0/9] xen: arm: reenable support for 32-bit userspace running in 64-bit guest Ian Campbell
2014-09-09 16:23 ` [PATCH 1/9] xen: arm: Correct PMXEV cp register definitions Ian Campbell
2014-09-09 23:04   ` Julien Grall
2014-09-09 16:23 ` [PATCH 2/9] xen: arm: Factor out psr_mode_is_user Ian Campbell
2014-09-09 23:08   ` Julien Grall
2014-09-09 16:23 ` [PATCH 3/9] xen: arm: Handle 32-bit EL0 on 64-bit EL1 when advancing PC after trap Ian Campbell
2014-09-09 23:12   ` Julien Grall
2014-09-09 16:23 ` [PATCH 4/9] xen: arm: turn vtimer traps for cp32/64 and sysreg into #undef Ian Campbell
2014-09-09 23:31   ` Julien Grall
2014-09-10  9:46     ` Ian Campbell
2014-09-10 18:54       ` Julien Grall
2014-09-11  8:43         ` Ian Campbell
2015-01-14 16:33           ` Ian Campbell
2015-01-14 16:57             ` Julien Grall
2015-01-15 10:26               ` Ian Campbell
2015-01-15 12:27                 ` Julien Grall
2015-01-15 12:35                   ` Ian Campbell
2014-09-09 16:23 ` [PATCH 5/9] xen: arm: Handle CP15 register traps from userspace Ian Campbell
2014-09-09 23:42   ` Julien Grall
2014-09-10  9:48     ` Ian Campbell
2014-09-10 18:56       ` Julien Grall [this message]
2014-09-18  1:31         ` Ian Campbell
2014-09-09 16:23 ` [PATCH 6/9] xen: arm: Handle CP14 32-bit register accesses " Ian Campbell
2014-09-09 23:45   ` Julien Grall
2014-09-10  9:48     ` Ian Campbell
2015-02-10  3:40       ` Ian Campbell
2015-02-10  4:14         ` Julien Grall
2014-09-09 16:23 ` [PATCH 7/9] xen: arm: correctly handle sysreg " Ian Campbell
2014-09-09 16:23 ` [PATCH 8/9] xen: arm: handle remaining traps " Ian Campbell
2014-09-09 16:23 ` [PATCH 9/9] xen: arm: Allow traps from 32 bit userspace on 64 bit hypervisors again Ian Campbell
2014-09-09 16:23 ` [RFC PATCH 0/9] xen: arm: reenable support for 32-bit userspace running in 64-bit guest Ian Campbell

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=54109EC9.1070303@linaro.org \
    --to=julien.grall@linaro.org \
    --cc=Ian.Campbell@citrix.com \
    --cc=stefano.stabellini@eu.citrix.com \
    --cc=tim@xen.org \
    --cc=xen-devel@lists.xen.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.