Commit 75c5a92e authored by Jacob Pan's avatar Jacob Pan Committed by Zheng Zengkai
Browse files

iommu: Add a timeout parameter for PRQ response 

maillist inclusion
category: feature
bugzilla: 51855
CVE: NA

Reference: https://jpbrucker.net/git/linux/commit/?h=sva/2021-03-01&id=2c56ef21daed0cd65da9b4907ce4b84c56ca7c1c



---------------------------------------------

When an I/O page request is processed outside the IOMMU subsystem,
response can be delayed or lost. Add a tunable setup parameter such that
user can choose the timeout for IOMMU to track pending page requests.

This timeout mechanism is a basic safety net which can be implemented in
conjunction with credit based or device level page response exception
handling.

Signed-off-by: default avatarJacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: default avatarLijun Fang <fanglijun3@huawei.com>
Reviewed-by: default avatarWeilong Chen <chenweilong@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 9ce88066

Documentation/admin-guide/kernel-parameters.txt

+8 −0
Original line number Diff line number Diff line
@@ -2019,6 +2019,14 @@ 
			1 - Bypass the IOMMU for DMA.

			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.



	iommu.prq_timeout=

			Timeout in seconds to wait for page response

			of a pending page request.

			Format: <integer>

			Default: 10

			0 - no timeout tracking

			1 to 100 - allowed range



	io7=		[HW] IO7 for Marvel-based Alpha systems

			See comment before marvel_specify_io7 in

			arch/alpha/kernel/core_marvel.c.

drivers/iommu/iommu.c

+33 −0
Original line number Diff line number Diff line
@@ -32,6 +32,19 @@ static unsigned int iommu_def_domain_type __read_mostly; 
static bool iommu_dma_strict __read_mostly = true;

static u32 iommu_cmd_line __read_mostly;



/*

 * Timeout to wait for page response of a pending page request. This is

 * intended as a basic safety net in case a pending page request is not

 * responded for an exceptionally long time. Device may also implement

 * its own protection mechanism against this exception.

 * Units are in jiffies with a range between 1 - 100 seconds equivalent.

 * Default to 10 seconds.

 * Setting 0 means no timeout tracking.

 */

#define IOMMU_PAGE_RESPONSE_MAX_TIMEOUT (HZ * 100)

#define IOMMU_PAGE_RESPONSE_DEF_TIMEOUT (HZ * 10)

static unsigned long prq_timeout = IOMMU_PAGE_RESPONSE_DEF_TIMEOUT;



struct iommu_group {

	struct kobject kobj;

	struct kobject *devices_kobj;
@@ -329,6 +342,26 @@ static int __init iommu_dma_setup(char *str) 
}

early_param("iommu.strict", iommu_dma_setup);



static int __init iommu_set_prq_timeout(char *str)

{

	int ret;

	unsigned long timeout;



	if (!str)

		return -EINVAL;



	ret = kstrtoul(str, 10, &timeout);

	if (ret)

		return ret;

	timeout = timeout * HZ;

	if (timeout > IOMMU_PAGE_RESPONSE_MAX_TIMEOUT)

		return -EINVAL;

	prq_timeout = timeout;



	return 0;

}

early_param("iommu.prq_timeout", iommu_set_prq_timeout);



static ssize_t iommu_group_attr_show(struct kobject *kobj,

				     struct attribute *__attr, char *buf)

{