x86, AMD IOMMU: add an emergency exit to the completion wait loop
To make the loop waiting for the completion wait command not wait forever this
patch adds a limit of cycles that loop.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: iommu@lists.linux-foundation.org
Cc: bhavna.sarathy@amd.com
Cc: robert.richter@amd.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 9098f04..7fa2d5d 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -32,6 +32,8 @@
#define to_pages(addr, size) \
(round_up(((addr) & ~PAGE_MASK) + (size), PAGE_SIZE) >> PAGE_SHIFT)
+#define EXIT_LOOP_COUNT 10000000
+
static DEFINE_RWLOCK(amd_iommu_devtable_lock);
/*
@@ -106,6 +108,7 @@
struct command cmd;
volatile u64 ready = 0;
unsigned long ready_phys = virt_to_phys(&ready);
+ unsigned long i = 0;
memset(&cmd, 0, sizeof(cmd));
cmd.data[0] = LOW_U32(ready_phys) | CMD_COMPL_WAIT_STORE_MASK;
@@ -120,8 +123,13 @@
if (ret)
return ret;
- while (!ready)
+ while (!ready && (i < EXIT_LOOP_COUNT)) {
+ ++i;
cpu_relax();
+ }
+
+ if (unlikely((i == EXIT_LOOP_COUNT) && printk_ratelimit()))
+ printk(KERN_WARNING "AMD IOMMU: Completion wait loop failed\n");
return 0;
}