Commit eee53537 authored by Joerg Roedel's avatar Joerg Roedel
Browse files

iommu/amd: Fix deadlock in ppr-handling error path 



In the error path of the ppr_notifer it can happen that the
iommu->lock is taken recursivly. This patch fixes the
problem by releasing the iommu->lock before any notifier is
invoked. This also requires to move the erratum workaround
for the ppr-log (interrupt may be faster than data in the log)
one function up.

Cc: stable@vger.kernel.org # v3.3, v3.4
Signed-off-by: default avatarJoerg Roedel <joerg.roedel@amd.com>
parent c1bf94ec

drivers/iommu/amd_iommu.c

+44 −27
Original line number Diff line number Diff line
@@ -547,26 +547,12 @@ static void iommu_poll_events(struct amd_iommu *iommu) 
	spin_unlock_irqrestore(&iommu->lock, flags);

}



static void iommu_handle_ppr_entry(struct amd_iommu *iommu, u32 head)

static void iommu_handle_ppr_entry(struct amd_iommu *iommu, u64 *raw)

{

	struct amd_iommu_fault fault;

	volatile u64 *raw;

	int i;



	INC_STATS_COUNTER(pri_requests);



	raw = (u64 *)(iommu->ppr_log + head);



	/*

	 * Hardware bug: Interrupt may arrive before the entry is written to

	 * memory. If this happens we need to wait for the entry to arrive.

	 */

	for (i = 0; i < LOOP_TIMEOUT; ++i) {

		if (PPR_REQ_TYPE(raw[0]) != 0)

			break;

		udelay(1);

	}



	if (PPR_REQ_TYPE(raw[0]) != PPR_REQ_FAULT) {

		pr_err_ratelimited("AMD-Vi: Unknown PPR request received\n");

		return;
@@ -578,12 +564,6 @@ static void iommu_handle_ppr_entry(struct amd_iommu *iommu, u32 head) 
	fault.tag       = PPR_TAG(raw[0]);

	fault.flags     = PPR_FLAGS(raw[0]);



	/*

	 * To detect the hardware bug we need to clear the entry

	 * to back to zero.

	 */

	raw[0] = raw[1] = 0;



	atomic_notifier_call_chain(&ppr_notifier, 0, &fault);

}
@@ -595,25 +575,62 @@ static void iommu_poll_ppr_log(struct amd_iommu *iommu) 
	if (iommu->ppr_log == NULL)

		return;



	/* enable ppr interrupts again */

	writel(MMIO_STATUS_PPR_INT_MASK, iommu->mmio_base + MMIO_STATUS_OFFSET);



	spin_lock_irqsave(&iommu->lock, flags);



	head = readl(iommu->mmio_base + MMIO_PPR_HEAD_OFFSET);

	tail = readl(iommu->mmio_base + MMIO_PPR_TAIL_OFFSET);



	while (head != tail) {

		volatile u64 *raw;

		u64 entry[2];

		int i;



		/* Handle PPR entry */

		iommu_handle_ppr_entry(iommu, head);

		raw = (u64 *)(iommu->ppr_log + head);



		/* Update and refresh ring-buffer state*/

		/*

		 * Hardware bug: Interrupt may arrive before the entry is

		 * written to memory. If this happens we need to wait for the

		 * entry to arrive.

		 */

		for (i = 0; i < LOOP_TIMEOUT; ++i) {

			if (PPR_REQ_TYPE(raw[0]) != 0)

				break;

			udelay(1);

		}



		/* Avoid memcpy function-call overhead */

		entry[0] = raw[0];

		entry[1] = raw[1];



		/*

		 * To detect the hardware bug we need to clear the entry

		 * back to zero.

		 */

		raw[0] = raw[1] = 0UL;



		/* Update head pointer of hardware ring-buffer */

		head = (head + PPR_ENTRY_SIZE) % PPR_LOG_SIZE;

		writel(head, iommu->mmio_base + MMIO_PPR_HEAD_OFFSET);



		/*

		 * Release iommu->lock because ppr-handling might need to

		 * re-aquire it

		 */

		spin_unlock_irqrestore(&iommu->lock, flags);



		/* Handle PPR entry */

		iommu_handle_ppr_entry(iommu, entry);



		spin_lock_irqsave(&iommu->lock, flags);



		/* Refresh ring-buffer information */

		head = readl(iommu->mmio_base + MMIO_PPR_HEAD_OFFSET);

		tail = readl(iommu->mmio_base + MMIO_PPR_TAIL_OFFSET);

	}



	/* enable ppr interrupts again */

	writel(MMIO_STATUS_PPR_INT_MASK, iommu->mmio_base + MMIO_STATUS_OFFSET);



	spin_unlock_irqrestore(&iommu->lock, flags);

}

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