Patch "ptdma: pt_core_execute_cmd() should use spinlock" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ptdma: pt_core_execute_cmd() should use spinlock

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ptdma-pt_core_execute_cmd-should-use-spinlock.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2324dff0579e30622cd6a671ba98614737a2ea48
Author: Eric Pilmore <epilmore@xxxxxxxxxx>
Date:   Wed Jan 18 19:39:08 2023 -0800

    ptdma: pt_core_execute_cmd() should use spinlock
    
    [ Upstream commit 95e5fda3b5f9ed8239b145da3fa01e641cf5d53c ]
    
    The interrupt handler (pt_core_irq_handler()) of the ptdma
    driver can be called from interrupt context. The code flow
    in this function can lead down to pt_core_execute_cmd() which
    will attempt to grab a mutex, which is not appropriate in
    interrupt context and ultimately leads to a kernel panic.
    The fix here changes this mutex to a spinlock, which has
    been verified to resolve the issue.
    
    Fixes: fa5d823b16a9 ("dmaengine: ptdma: Initial driver for the AMD PTDMA")
    Signed-off-by: Eric Pilmore <epilmore@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230119033907.35071-1-epilmore@xxxxxxxxxx
    Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/dma/ptdma/ptdma-dev.c b/drivers/dma/ptdma/ptdma-dev.c
index daafea5bc35d..bca4063b0dce 100644
--- a/drivers/dma/ptdma/ptdma-dev.c
+++ b/drivers/dma/ptdma/ptdma-dev.c
@@ -71,12 +71,13 @@ static int pt_core_execute_cmd(struct ptdma_desc *desc, struct pt_cmd_queue *cmd
 	bool soc = FIELD_GET(DWORD0_SOC, desc->dw0);
 	u8 *q_desc = (u8 *)&cmd_q->qbase[cmd_q->qidx];
 	u32 tail;
+	unsigned long flags;
 
 	if (soc) {
 		desc->dw0 |= FIELD_PREP(DWORD0_IOC, desc->dw0);
 		desc->dw0 &= ~DWORD0_SOC;
 	}
-	mutex_lock(&cmd_q->q_mutex);
+	spin_lock_irqsave(&cmd_q->q_lock, flags);
 
 	/* Copy 32-byte command descriptor to hw queue. */
 	memcpy(q_desc, desc, 32);
@@ -91,7 +92,7 @@ static int pt_core_execute_cmd(struct ptdma_desc *desc, struct pt_cmd_queue *cmd
 
 	/* Turn the queue back on using our cached control register */
 	pt_start_queue(cmd_q);
-	mutex_unlock(&cmd_q->q_mutex);
+	spin_unlock_irqrestore(&cmd_q->q_lock, flags);
 
 	return 0;
 }
@@ -197,7 +198,7 @@ int pt_core_init(struct pt_device *pt)
 
 	cmd_q->pt = pt;
 	cmd_q->dma_pool = dma_pool;
-	mutex_init(&cmd_q->q_mutex);
+	spin_lock_init(&cmd_q->q_lock);
 
 	/* Page alignment satisfies our needs for N <= 128 */
 	cmd_q->qsize = Q_SIZE(Q_DESC_SIZE);
diff --git a/drivers/dma/ptdma/ptdma.h b/drivers/dma/ptdma/ptdma.h
index afbf192c9230..0f0b400a864e 100644
--- a/drivers/dma/ptdma/ptdma.h
+++ b/drivers/dma/ptdma/ptdma.h
@@ -196,7 +196,7 @@ struct pt_cmd_queue {
 	struct ptdma_desc *qbase;
 
 	/* Aligned queue start address (per requirement) */
-	struct mutex q_mutex ____cacheline_aligned;
+	spinlock_t q_lock ____cacheline_aligned;
 	unsigned int qidx;
 
 	unsigned int qsize;