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: Borislav Petkov <bp@alien8.de>
Signed-off-by: Joerg 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: Ingo Molnar <mingo@kernel.org>
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 96de97a..4025291 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -940,15 +940,13 @@
* 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,
- struct iommu_cmd *cmd,
- bool sync)
+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 @@
if (left <= 2) {
struct iommu_cmd sync_cmd;
- volatile u64 sem = 0;
int ret;
- build_completion_wait(&sync_cmd, (u64)&sem);
+ iommu->cmd_sem = 0;
+
+ build_completion_wait(&sync_cmd, (u64)&iommu->cmd_sem);
copy_cmd_to_buffer(iommu, &sync_cmd, tail);
- spin_unlock_irqrestore(&iommu->lock, flags);
-
- if ((ret = wait_on_sem(&sem)) != 0)
+ if ((ret = wait_on_sem(&iommu->cmd_sem)) != 0)
return ret;
goto again;
@@ -976,9 +973,21 @@
/* 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_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)
diff --git a/drivers/iommu/amd_iommu_types.h b/drivers/iommu/amd_iommu_types.h
index caf5e38..9652848 100644
--- a/drivers/iommu/amd_iommu_types.h
+++ b/drivers/iommu/amd_iommu_types.h
@@ -524,6 +524,8 @@
struct irq_domain *ir_domain;
struct irq_domain *msi_domain;
#endif
+
+ volatile u64 __aligned(8) cmd_sem;
};
#define ACPIHID_UID_LEN 256