From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: andre.przywara@arm.com, steve.capper@arm.com, wei.chen@arm.com,
xen-devel@lists.xen.org
Subject: Re: [RFC 15/16] xen/arm: traps: Don't inject a fault if the translation VA -> IPA fails
Date: Mon, 23 May 2016 14:45:49 +0100 [thread overview]
Message-ID: <5743098D.5000807@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1605211549550.2958@sstabellini-ThinkPad-X260>
Hi Stefano,
On 21/05/16 15:51, Stefano Stabellini wrote:
> On Sat, 21 May 2016, Stefano Stabellini wrote:
>> On Thu, 5 May 2016, Julien Grall wrote:
>>> Based on ARM ARM (D4.5.3 in ARM DDI 0486A and B3.12.7 in ARM DDI 0406C.c),
>>> a Stage 1 translation error has priority over a Stage 2 translation error.
>>>
>>> Therefore gva_to_ipa can only fail if another vCPU is playing with the
>>> page table.
>>>
>>> Rather than injecting a custom fault, replay the instruction and let the
>>> processor injecting the correct fault.
>>>
>>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>
>> Couldn't a guest purposely cause a DoS in the hypervisor this way?
>
> Just double-checking. I am pretty sure it cannot, because the replayed
> instruction won't cause another hypervisor trap the second time around.
Before returning to the guest vCPU, Xen is handling any pending softirqs
(see leave_hypervisor_tail). It might be possible to have the vCPU
rescheduled.
So even if the replay cause another hypervisor trap, it will only impact
its timeslice.
I will update the commit message to explain why it is not possible.
Regards,
--
Julien Grall
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next prev parent reply other threads:[~2016-05-23 13:45 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-05 16:34 [RFC 00/16] xen/arm: Introduce alternative runtime patching for ARM64 Julien Grall
2016-05-05 16:34 ` [RFC 01/16] xen/arm: Makefile: Sort the entries alphabetically Julien Grall
2016-05-09 9:34 ` Stefano Stabellini
2016-05-05 16:34 ` [RFC 02/16] xen/arm: Include the header asm-arm/system.h in asm-arm/page.h Julien Grall
2016-05-09 9:34 ` Stefano Stabellini
2016-05-05 16:34 ` [RFC 03/16] xen/arm: Add macros to handle the MIDR Julien Grall
2016-05-09 9:37 ` Stefano Stabellini
2016-05-05 16:34 ` [RFC 04/16] xen/arm: arm64: Import flush_icache_range from Linux v4.6-rc3 Julien Grall
2016-05-09 9:40 ` Julien Grall
2016-05-05 16:34 ` [RFC 05/16] xen/arm: Add cpu_hwcap bitmap Julien Grall
2016-05-09 9:53 ` Stefano Stabellini
2016-05-09 10:02 ` Julien Grall
2016-05-05 16:34 ` [RFC 06/16] xen/arm64: Add an helper to invalidate all instruction caches Julien Grall
2016-05-09 9:50 ` Stefano Stabellini
2016-05-05 16:34 ` [RFC 07/16] xen/arm: arm64: Move the define BRK_BUG_FRAME into a separate header Julien Grall
2016-05-09 9:55 ` Stefano Stabellini
2016-05-05 16:34 ` [RFC 08/16] xen/arm: arm64: Reserve a brk immediate to fault on purpose Julien Grall
2016-05-09 9:58 ` Stefano Stabellini
2016-05-05 16:34 ` [RFC 09/16] xen/arm: arm64: Add helpers to decode and encode branch instructions Julien Grall
2016-05-09 10:05 ` Stefano Stabellini
2016-05-09 13:04 ` Julien Grall
2016-05-23 10:52 ` Julien Grall
2016-05-13 20:35 ` Konrad Rzeszutek Wilk
2016-05-14 10:49 ` Julien Grall
2016-05-05 16:34 ` [RFC 10/16] xen/arm: Introduce alternative runtime patching Julien Grall
2016-05-13 20:26 ` Konrad Rzeszutek Wilk
2016-05-14 18:02 ` Julien Grall
2016-05-21 15:09 ` Stefano Stabellini
2016-05-23 11:11 ` Julien Grall
2016-05-30 14:45 ` Stefano Stabellini
2016-05-30 16:42 ` Julien Grall
2016-05-31 9:21 ` Stefano Stabellini
2016-05-31 10:24 ` Julien Grall
2016-06-02 14:46 ` Konrad Rzeszutek Wilk
2016-06-02 15:04 ` Julien Grall
2016-06-02 15:14 ` Julien Grall
2016-06-06 14:17 ` Konrad Rzeszutek Wilk
2016-06-06 14:18 ` Julien Grall
2016-05-05 16:34 ` [RFC 11/16] xen/arm: Detect silicon revision and set cap bits accordingly Julien Grall
2016-05-13 20:37 ` Konrad Rzeszutek Wilk
2016-05-14 18:04 ` Julien Grall
2016-05-16 13:50 ` Konrad Rzeszutek Wilk
2016-05-16 13:54 ` Julien Grall
2016-05-05 16:34 ` [RFC 12/16] xen/arm: Document the errata implemented in Xen Julien Grall
2016-05-05 16:34 ` [RFC 13/16] xen/arm: arm64: Add Cortex-A53 cache errata workaround Julien Grall
2016-05-21 14:40 ` Stefano Stabellini
2016-05-23 13:39 ` Julien Grall
2016-05-05 16:34 ` [RFC 14/16] xen/arm: arm64: Add cortex-A57 erratum 832075 workaround Julien Grall
2016-05-05 16:34 ` [RFC 15/16] xen/arm: traps: Don't inject a fault if the translation VA -> IPA fails Julien Grall
2016-05-21 14:42 ` Stefano Stabellini
2016-05-21 14:51 ` Stefano Stabellini
2016-05-23 13:45 ` Julien Grall [this message]
2016-05-05 16:34 ` [RFC 16/16] xen/arm: arm64: Document Cortex-A57 erratum 834220 Julien Grall
2016-05-05 16:38 ` [RFC 00/16] xen/arm: Introduce alternative runtime patching for ARM64 Julien Grall
2016-05-11 2:28 ` Wei Chen
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