Re: [PATCH v7 08/19] iommu: Implement reserved_regions iommu-group sysfs file

Auger Eric
2017-01-10T16:20:43Z

Hi Joerg,

On 09/01/2017 14:45, Eric Auger wrote:
> A new iommu-group sysfs attribute file is introduced. It contains
> the list of reserved regions for the iommu-group. Each reserved
> region is described on a separate line:
> - first field is the start IOVA address,
> - second is the end IOVA address,
> - third is the type.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
> v6 -> v7:
> - also report the type of the reserved region as a string
> - updated ABI documentation
>
> v3 -> v4:
> - add cast to long long int when printing to avoid warning on
> i386
> - change S_IRUGO into 0444
> - remove sort. The list is natively sorted now.
>
> The file layout is inspired of /sys/bus/pci/devices/BDF/resource.
> I also read Documentation/filesystems/sysfs.txt so I expect this
> to be frowned upon.
> ---
> .../ABI/testing/sysfs-kernel-iommu_groups | 12 +++++++
> drivers/iommu/iommu.c | 38 ++++++++++++++++++++++
> 2 files changed, 50 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> index 9b31556..35c64e0 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> @@ -12,3 +12,15 @@ Description: /sys/kernel/iommu_groups/ contains a number of sub-
> file if the IOMMU driver has chosen to register a more
> common name for the group.
> Users:
> +
> +What: /sys/kernel/iommu_groups/reserved_regions
> +Date: January 2017
> +KernelVersion: v4.11
> +Contact: Eric Auger <eric.auger@redhat.com>
> +Description: /sys/kernel/iommu_groups/reserved_regions list IOVA
> + regions that are reserved. Not necessarily all
> + reserved regions are listed. This is typically used to
> + output direct-mapped, MSI, non mappable regions. Each
> + region is described on a single line: the 1st field is
> + the base IOVA, the second is the end IOVA and the third
> + field describes the type of the region.
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 640056b..0123daa 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -68,6 +68,12 @@ struct iommu_group_attribute {
> const char *buf, size_t count);
> };
>
> +static const char * const iommu_group_resv_type_string[] = {
> + [IOMMU_RESV_DIRECT] = "direct",
> + [IOMMU_RESV_RESERVED] = "reserved",
> + [IOMMU_RESV_MSI] = "msi",
> +};
> +
> #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store) \
> struct iommu_group_attribute iommu_group_attr_##_name = \
> __ATTR(_name, _mode, _show, _store)
> @@ -231,8 +237,33 @@ int iommu_get_group_resv_regions(struct iommu_group *group,
> }
> EXPORT_SYMBOL_GPL(iommu_get_group_resv_regions);
>
> +static ssize_t iommu_group_show_resv_regions(struct iommu_group *group,
> + char *buf)
> +{
> + struct iommu_resv_region *region, *next;
> + struct list_head group_resv_regions;
> + char *str = buf;
> +
> + INIT_LIST_HEAD(&group_resv_regions);
> + iommu_get_group_resv_regions(group, &group_resv_regions);
> +
> + list_for_each_entry_safe(region, next, &group_resv_regions, list) {
> + str += sprintf(str, "0x%016llx 0x%016llx %s\n",
> + (long long int)region->start,
> + (long long int)(region->start +
> + region->length - 1),
> + iommu_group_resv_type_string[region->type]);
> + kfree(region);
> + }
> +
> + return (str - buf);
> +}
> +
> static IOMMU_GROUP_ATTR(name, S_IRUGO, iommu_group_show_name, NULL);
>
> +static IOMMU_GROUP_ATTR(reserved_regions, 0444,
> + iommu_group_show_resv_regions, NULL);
> +
> static void iommu_group_release(struct kobject *kobj)
> {
> struct iommu_group *group = to_iommu_group(kobj);
> @@ -247,6 +278,8 @@ static void iommu_group_release(struct kobject *kobj)
> if (group->default_domain)
> iommu_domain_free(group->default_domain);
>
> + iommu_group_remove_file(group, &iommu_group_attr_reserved_regions);

The /sys/kernel/iommu_groups/n directory seems to be removed before this
gets called and this may produce a WARNING when devices get removed from
the group. I intend to remove the call since I have the feeling
everything gets cleaned up properly.

Do you see any issue?

Thanks

Eric

[ 350.753618] iommu: Removing device 0000:01:10.0 from group 7
[ 350.759331] kernfs: can not remove 'reserved_regions', no directory
[ 350.765603] ------------[ cut here ]------------
[ 350.770216] WARNING: CPU: 3 PID: 2617 at fs/kernfs/dir.c:1406
kernfs_remove_by_name_ns+0x8c/0x98
../..
[ 351.028154] [<ffff00000828819c>] kernfs_remove_by_name_ns+0x8c/0x98
[ 351.034414] [<ffff000008289bf8>] sysfs_remove_file_ns+0x14/0x1c
[ 351.040325] [<ffff00000856d918>] iommu_group_release+0x68/0x9c
[ 351.046150] [<ffff0000083d152c>] kobject_cleanup+0x8c/0x194
[ 351.051715] [<ffff0000083d13c8>] kobject_put+0x44/0x6c
[ 351.056844] [<ffff0000083d1490>] kobject_del+0x40/0x50
[ 351.061974] [<ffff0000083d1508>] kobject_cleanup+0x68/0x194
[ 351.067538] [<ffff0000083d13c8>] kobject_put+0x44/0x6c
[ 351.072668] [<ffff00000856df30>] iommu_group_remove_device+0x128/0x1d4
[ 351.079187] [<ffff000008575eb0>] arm_smmu_remove_device+0x12c/0x158

> +
> kfree(group->name);
> kfree(group);
> }
> @@ -310,6 +343,11 @@ struct iommu_group *iommu_group_alloc(void)
> */
> kobject_put(&group->kobj);
>
> + ret = iommu_group_create_file(group,
> + &iommu_group_attr_reserved_regions);
> + if (ret)
> + return ERR_PTR(ret);
> +
> pr_debug("Allocated group %d\n", group->id);
>
> return group;
>