linux-kernel - Re: [PATCH] iommu/amd: Use raw_cpu_ptr() instead of get_cpu_ptr() for ->flush

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Message-ID: <20170919094119.bibxslqyeefbx7gf@8bytes.org>
Date:   Tue, 19 Sep 2017 11:41:19 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     iommu@...ts.linux-foundation.org, vinadhy@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/amd: Use raw_cpu_ptr() instead of get_cpu_ptr()
 for ->flush_queue

Hi Sebastian,

On Wed, Sep 06, 2017 at 12:34:59PM +0200, Sebastian Andrzej Siewior wrote:
> get_cpu_ptr() disables preemption and returns the ->flush_queue object
> of the current CPU. raw_cpu_ptr() does the same except that it not
> disable preemption which means the scheduler can move it to another CPU
> after it obtained the per-CPU object.
> In this case this is not bad because the data structure itself is
> protected with a spin_lock. This change shouldn't matter in general
> but on RT it does because the sleeping lock can't be accessed with
> disabled preemption.

I moved the flushing to driver/iommu/iova.c to share it with the Intel
IOMMU and possibly other drivers too, so this patch does no longer apply
to v4.14-rc1. Can you update the patch to these changes?

Regards,

	Joerg