[PATCH v2] iommu/iova: Use raw_cpu_ptr() instead of get_cpu_ptr() for ->fq

Path	csiph.com!news.mixmin.net!aioe.org!bofh.it!news.nic.it!robomod
From	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Newsgroups	linux.kernel
Subject	[PATCH v2] iommu/iova: Use raw_cpu_ptr() instead of get_cpu_ptr() for ->fq
Date	Thu, 21 Sep 2017 17:30:02 +0200
Message-ID	<usbAm-2Ne-11@gated-at.bofh.it> (permalink)
References	<umFUv-oN-11@gated-at.bofh.it> <urnkf-39c-33@gated-at.bofh.it>
X-Original-To	Joerg Roedel <joro@8bytes.org>
MIME-Version	1.0
Content-Type	text/plain; charset=utf-8
Content-Disposition	inline
Content-Transfer-Encoding	8BIT
User-Agent	NeoMutt/20170609 (1.8.3)
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	53
Organization	linux.* mail to news gateway
X-Original-Cc	iommu@lists.linux-foundation.org, vinadhy@gmail.com, linux-kernel@vger.kernel.org
X-Original-Date	Thu, 21 Sep 2017 17:21:40 +0200
X-Original-Message-ID	<20170921152140.grayy3a7ok2im7xa@linutronix.de>
X-Original-References	<20170906103459.oi2nn7jondjqdo5m@linutronix.de> <20170919094119.bibxslqyeefbx7gf@8bytes.org>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1736773

Show key headers only | View raw

get_cpu_ptr() disabled preemption and returns the ->fq 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 however on RT
it does because the sleeping lock can't be accessed with disabled
preemption.

Cc: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org
Reported-by: vinadhy@gmail.com
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
On 2017-09-19 11:41:19 [+0200], Joerg Roedel wrote:
> Hi Sebastian,
Hi Jörg,

> 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?

Sure.

v1…v2: move the change from amd_iommu.c to iova.c

 drivers/iommu/iova.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 33edfa794ae9..b30900025c62 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -570,7 +570,7 @@ void queue_iova(struct iova_domain *iovad,
 		unsigned long pfn, unsigned long pages,
 		unsigned long data)
 {
-	struct iova_fq *fq = get_cpu_ptr(iovad->fq);
+	struct iova_fq *fq = raw_cpu_ptr(iovad->fq);
 	unsigned long flags;
 	unsigned idx;
 
@@ -600,8 +600,6 @@ void queue_iova(struct iova_domain *iovad,
 	if (atomic_cmpxchg(&iovad->fq_timer_on, 0, 1) == 0)
 		mod_timer(&iovad->fq_timer,
 			  jiffies + msecs_to_jiffies(IOVA_FQ_TIMEOUT));
-
-	put_cpu_ptr(iovad->fq);
 }
 EXPORT_SYMBOL_GPL(queue_iova);
 
-- 
2.14.1

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: [PATCH] iommu/amd: Use raw_cpu_ptr() instead of get_cpu_ptr()  for ->flush_queue Joerg Roedel <joro@8bytes.org> - 2017-09-19 11:50 +0200
  [PATCH v2] iommu/iova: Use raw_cpu_ptr() instead of get_cpu_ptr()  for ->fq Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-09-21 17:30 +0200

csiph-web