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x86, AMD IOMMU: add an emergency exit to the completion wait loop

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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>
This commit is contained in:
Joerg Roedel 2008-07-11 17:14:27 +02:00 committed by Ingo Molnar
parent 9a836de0c9
commit 136f78a19c
1 changed files with 9 additions and 1 deletions
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10
arch/x86/kernel/amd_iommu.c
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@ -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 @@ static int iommu_completion_wait(struct amd_iommu *iommu)
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 @@ static int iommu_completion_wait(struct amd_iommu *iommu)
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;
}