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    Subject[PATCH RT 11/15] iommu/amd: Use raw_cpu_ptr() instead of get_cpu_ptr() for ->flush_queue
    4.9.65-rt57-rc2 stable review patch.
    If anyone has any objections, please let me know.

    ------------------

    From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

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

    Cc: stable-rt@vger.kernel.org
    Cc: Joerg Roedel <joro@8bytes.org>
    Cc: iommu@lists.linux-foundation.org
    Reported-by: Vinod Adhikary <vinadhy@gmail.com>
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    ---
    drivers/iommu/amd_iommu.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
    index a88595b21111..ff5c2424eb9e 100644
    --- a/drivers/iommu/amd_iommu.c
    +++ b/drivers/iommu/amd_iommu.c
    @@ -2283,7 +2283,7 @@ static void queue_add(struct dma_ops_domain *dma_dom,
    pages = __roundup_pow_of_two(pages);
    address >>= PAGE_SHIFT;

    - queue = get_cpu_ptr(&flush_queue);
    + queue = raw_cpu_ptr(&flush_queue);
    spin_lock_irqsave(&queue->lock, flags);

    if (queue->next == FLUSH_QUEUE_SIZE)
    @@ -2300,8 +2300,6 @@ static void queue_add(struct dma_ops_domain *dma_dom,

    if (atomic_cmpxchg(&queue_timer_on, 0, 1) == 0)
    mod_timer(&queue_timer, jiffies + msecs_to_jiffies(10));
    -
    - put_cpu_ptr(&flush_queue);
    }


    --
    2.13.2

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