Commit 4bf5beef authored by Joerg Roedel's avatar Joerg Roedel Committed by Ingo Molnar
Browse files

iommu/amd: Don't put completion-wait semaphore on stack 



The semaphore used by the AMD IOMMU to signal command
completion lived on the stack until now, which was safe as
the driver busy-waited on the semaphore with IRQs disabled,
so the stack can't go away under the driver.

But the recently introduced vmap-based stacks break this as
the physical address of the semaphore can't be determinded
easily anymore. The driver used the __pa() macro, but that
only works in the direct-mapping. The result were
Completion-Wait timeout errors seen by the IOMMU driver,
breaking system boot.

Since putting the semaphore on the stack is bad design
anyway, move the semaphore into 'struct amd_iommu'. It is
protected by the per-iommu lock and now in the direct
mapping again. This fixes the Completion-Wait timeout errors
and makes AMD IOMMU systems boot again with vmap-based
stacks enabled.

Reported-by: default avatarBorislav Petkov <bp@alien8.de>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 15f4eae7

drivers/iommu/amd_iommu.c

+35 −16
Original line number Diff line number Diff line
@@ -940,15 +940,13 @@ static void build_inv_irt(struct iommu_cmd *cmd, u16 devid) 
 * Writes the command to the IOMMUs command buffer and informs the

 * hardware about the new command.

 */

static int iommu_queue_command_sync(struct amd_iommu *iommu,

static int __iommu_queue_command_sync(struct amd_iommu *iommu,

				      struct iommu_cmd *cmd,

				      bool sync)

{

	u32 left, tail, head, next_tail;

	unsigned long flags;



again:

	spin_lock_irqsave(&iommu->lock, flags);



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

	tail      = readl(iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
@@ -957,15 +955,14 @@ again: 


	if (left <= 2) {

		struct iommu_cmd sync_cmd;

		volatile u64 sem = 0;

		int ret;



		build_completion_wait(&sync_cmd, (u64)&sem);

		copy_cmd_to_buffer(iommu, &sync_cmd, tail);

		iommu->cmd_sem = 0;



		spin_unlock_irqrestore(&iommu->lock, flags);

		build_completion_wait(&sync_cmd, (u64)&iommu->cmd_sem);

		copy_cmd_to_buffer(iommu, &sync_cmd, tail);



		if ((ret = wait_on_sem(&sem)) != 0)

		if ((ret = wait_on_sem(&iommu->cmd_sem)) != 0)

			return ret;



		goto again;
@@ -976,9 +973,21 @@ again: 
	/* We need to sync now to make sure all commands are processed */

	iommu->need_sync = sync;



	return 0;

}



static int iommu_queue_command_sync(struct amd_iommu *iommu,

				    struct iommu_cmd *cmd,

				    bool sync)

{

	unsigned long flags;

	int ret;



	spin_lock_irqsave(&iommu->lock, flags);

	ret = __iommu_queue_command_sync(iommu, cmd, sync);

	spin_unlock_irqrestore(&iommu->lock, flags);



	return 0;

	return ret;

}



static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
@@ -993,19 +1002,29 @@ static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd) 
static int iommu_completion_wait(struct amd_iommu *iommu)

{

	struct iommu_cmd cmd;

	volatile u64 sem = 0;

	unsigned long flags;

	int ret;



	if (!iommu->need_sync)

		return 0;



	build_completion_wait(&cmd, (u64)&sem);



	ret = iommu_queue_command_sync(iommu, &cmd, false);

	build_completion_wait(&cmd, (u64)&iommu->cmd_sem);



	spin_lock_irqsave(&iommu->lock, flags);



	iommu->cmd_sem = 0;



	ret = __iommu_queue_command_sync(iommu, &cmd, false);

	if (ret)

		return ret;

		goto out_unlock;



	return wait_on_sem(&sem);

	ret = wait_on_sem(&iommu->cmd_sem);



out_unlock:

	spin_unlock_irqrestore(&iommu->lock, flags);



	return ret;

}



static int iommu_flush_dte(struct amd_iommu *iommu, u16 devid)

drivers/iommu/amd_iommu_types.h

+2 −0
Original line number Diff line number Diff line
@@ -524,6 +524,8 @@ struct amd_iommu { 
	struct irq_domain *ir_domain;

	struct irq_domain *msi_domain;

#endif



	volatile u64 __aligned(8) cmd_sem;

};



#define ACPIHID_UID_LEN 256

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