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Commit 136f78a1 authored by Joerg Roedel's avatar Joerg Roedel Committed by Ingo Molnar
Browse files

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: default avatarJoerg Roedel <joerg.roedel@amd.com>
Cc: iommu@lists.linux-foundation.org
Cc: bhavna.sarathy@amd.com
Cc: robert.richter@amd.com
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9a836de0

arch/x86/kernel/amd_iommu.c

+9 −1
Original line number Diff line number Diff line
@@ -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;

}