linux-kernel - Re: [PATCH 0/3] irqchip/gic-v4: Fix VMAPP/VMOVP races

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Message-ID: <42e08881-5faf-a78c-0d94-2a48415bc655@huawei.com>
Date: Wed, 17 Jul 2024 16:41:30 +0800
From: Tangnianyao <tangnianyao@...wei.com>
To: Marc Zyngier <maz@...nel.org>, <kvmarm@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC: Thomas Gleixner <tglx@...utronix.de>, "guoyang (C)" <guoyang2@...wei.com>,
	jiangkunkun <jiangkunkun@...wei.com>, wangwudi <wangwudi@...ilicon.com>
Subject: Re: [PATCH 0/3] irqchip/gic-v4: Fix VMAPP/VMOVP races

Hi, Marc

I meet another problem while fixing this in kernel 5.10.

Kernel 5.10 does not support guard and we replace it with raw_spin_lock/unlock.

When guest insmod nic drivers, it trigger host cpu power off somehow. The same

testcase runs quite good in kernel 6.6(both host and guest).

Would you fix this on long-term kernel 5.10? Or any sugguestion?


Thanks for your help.

Nianyao Tang



On 7/8/2024 10:02, Tangnianyao wrote:
>
> On 7/5/2024 17:31, Marc Zyngier wrote:
>> In 20240701072305.4129823-1-tangnianyao@...wei.com, Nianyao reports
>> a number of possible races that can trigger on GICv4 implementations
>> using the ITSList feature.
>>
>> These races involve concurrent VMOVP and VMAPP, the former happening
>> on vcpu load, while the latter is triggered on the first device being
>> MAPTI'd on a given ITS for this particular guest.
>>
>> The main issue is that we want to establish the affinity at VMAPP time,
>> while vcpu_load wants to set the affinity where the vcpu actually runs.
>> Lock ordering constraints mean that we can't lock the VPE on VMAPP,
>> so things are modified without any lock. What could possibly go wrong?
>>
>> THe fix is a bit involved, and relies on 3 things:
>>
>> - Making sure that the initial affinity of a VPE is fixed at activate
>>   time, which is done early in the life of the vcpup, before it can run.
>>
>> - Add a per-VM lock that can be taken instead of the global vmovp_lock,
>>   paving the way for a more manageable lock order.
>>
>> - Take the per-VPE lock whenever modifying the VPE affinity, as expected
>>   everywhere else in the code.
>>
>> With that, VMAPP and VMOVP can now run concurrently and still lead to
>> sensible results.
>>
>> Marc Zyngier (3):
>>   irqchip/gic-v4: Always configure affinity on VPE activation
>>   irqchip/gic-v4: Substitute vmovp_lock for a per-VM lock
>>   irqchip/gic-v4: Make sure a VPE is locked when VMAPP is issued
>>
>>  drivers/irqchip/irq-gic-v3-its.c   | 48 ++++++++++++++----------------
>>  include/linux/irqchip/arm-gic-v4.h |  8 +++++
>>  2 files changed, 30 insertions(+), 26 deletions(-)
>>
> I've tested this patch series. It works.
>
> Tested-by: Nianyao Tang <tangnianyao@...wei.com>
>
> .
>