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
next prev parent 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
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