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

From: Sebastian Andrzej Siewior
Date: Thu Sep 21 2017 - 11:21:48 EST

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

Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: vinadhy@xxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
On 2017-09-19 11:41:19 [+0200], Joerg Roedel wrote:
> Hi Sebastian,
Hi JÃrg,

> 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?


v1âv2: 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)
jiffies + msecs_to_jiffies(IOVA_FQ_TIMEOUT));
- put_cpu_ptr(iovad->fq);