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: Jacob Pan <jacob.jun....@linux.intel.com> --- Documentation/admin-guide/kernel-parameters.txt | 8 ++++++ drivers/iommu/iommu.c | 33 +++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 47d981a..7da5a83 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1817,6 +1817,14 @@ 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. diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 0c674d8..5b26499 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -33,6 +33,19 @@ static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA; #endif static bool iommu_dma_strict __read_mostly = true; +/* + * Timeout to wait for page response of a pending page request. This is + * intended as a basic safty 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; @@ -176,6 +189,26 @@ 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) { -- 2.7.4 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu