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Date: Thu, 7 Apr 2022 16:21:17 +0800
From: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To: John Garry <john.garry@...wei.com>, <joro@...tes.org>,
<will@...nel.org>, <robin.murphy@....com>
CC: <mst@...hat.com>, <jasowang@...hat.com>,
<iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
<virtualization@...ts.linux-foundation.org>,
<chenxiang66@...ilicon.com>, <jean-philippe@...aro.org>,
<linuxarm@...wei.com>
Subject: Re: [PATCH RESEND v5 4/5] iommu: Allow max opt DMA len be set for a
group via sysfs
On 2022/4/4 19:27, John Garry wrote:
> Add support to allow the maximum optimised DMA len be set for an IOMMU
> group via sysfs.
>
> This is much the same with the method to change the default domain type
> for a group.
>
> Signed-off-by: John Garry <john.garry@...wei.com>
> ---
> .../ABI/testing/sysfs-kernel-iommu_groups | 16 +++++
> drivers/iommu/iommu.c | 59 ++++++++++++++++++-
> include/linux/iommu.h | 6 ++
> 3 files changed, 79 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> index b15af6a5bc08..ed6f72794f6c 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> @@ -63,3 +63,19 @@ Description: /sys/kernel/iommu_groups/<grp_id>/type shows the type of default
> system could lead to catastrophic effects (the users might
> need to reboot the machine to get it to normal state). So, it's
> expected that the users understand what they're doing.
> +
> +What: /sys/kernel/iommu_groups/<grp_id>/max_opt_dma_size
> +Date: Feb 2022
> +KernelVersion: v5.18
> +Contact: iommu@...ts.linux-foundation.org
> +Description: /sys/kernel/iommu_groups/<grp_id>/max_opt_dma_size shows the
> + max optimised DMA size for the default IOMMU domain associated
> + with the group.
> + Each IOMMU domain has an IOVA domain. The IOVA domain caches
> + IOVAs upto a certain size as a performance optimisation.
> + This sysfs file allows the range of the IOVA domain caching be
> + set, such that larger than default IOVAs may be cached.
> + A value of 0 means that the default caching range is chosen.
> + A privileged user could request the kernel the change the range
> + by writing to this file. For this to happen, the same rules
> + and procedure applies as in changing the default domain type.
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 10bb10c2a210..7c7258f19bed 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -48,6 +48,7 @@ struct iommu_group {
> struct iommu_domain *default_domain;
> struct iommu_domain *domain;
> struct list_head entry;
> + size_t max_opt_dma_size;
> };
>
> struct group_device {
> @@ -89,6 +90,9 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
> static struct iommu_group *iommu_group_get_for_dev(struct device *dev);
> static ssize_t iommu_group_store_type(struct iommu_group *group,
> const char *buf, size_t count);
> +static ssize_t iommu_group_store_max_opt_dma_size(struct iommu_group *group,
> + const char *buf,
> + size_t count);
>
> #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store) \
> struct iommu_group_attribute iommu_group_attr_##_name = \
> @@ -571,6 +575,12 @@ static ssize_t iommu_group_show_type(struct iommu_group *group,
> return strlen(type);
> }
>
> +static ssize_t iommu_group_show_max_opt_dma_size(struct iommu_group *group,
> + char *buf)
> +{
> + return sprintf(buf, "%zu\n", group->max_opt_dma_size);
> +}
> +
> static IOMMU_GROUP_ATTR(name, S_IRUGO, iommu_group_show_name, NULL);
>
> static IOMMU_GROUP_ATTR(reserved_regions, 0444,
> @@ -579,6 +589,9 @@ static IOMMU_GROUP_ATTR(reserved_regions, 0444,
> static IOMMU_GROUP_ATTR(type, 0644, iommu_group_show_type,
> iommu_group_store_type);
>
> +static IOMMU_GROUP_ATTR(max_opt_dma_size, 0644, iommu_group_show_max_opt_dma_size,
> + iommu_group_store_max_opt_dma_size);
> +
> static void iommu_group_release(struct kobject *kobj)
> {
> struct iommu_group *group = to_iommu_group(kobj);
> @@ -665,6 +678,10 @@ struct iommu_group *iommu_group_alloc(void)
> if (ret)
> return ERR_PTR(ret);
>
> + ret = iommu_group_create_file(group, &iommu_group_attr_max_opt_dma_size);
> + if (ret)
> + return ERR_PTR(ret);
> +
> pr_debug("Allocated group %d\n", group->id);
>
> return group;
> @@ -2087,6 +2104,11 @@ struct iommu_domain *iommu_get_dma_domain(struct device *dev)
> return dev->iommu_group->default_domain;
> }
>
> +size_t iommu_group_get_max_opt_dma_size(struct iommu_group *group)
> +{
> + return group->max_opt_dma_size;
> +}
> +
> /*
> * IOMMU groups are really the natural working unit of the IOMMU, but
> * the IOMMU API works on domains and devices. Bridge that gap by
> @@ -2871,12 +2893,14 @@ EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
> * @prev_dev: The device in the group (this is used to make sure that the device
> * hasn't changed after the caller has called this function)
> * @type: The type of the new default domain that gets associated with the group
> + * @max_opt_dma_size: Set the IOMMU group max_opt_dma_size if non-zero
> *
> * Returns 0 on success and error code on failure
> *
> */
> static int iommu_change_dev_def_domain(struct iommu_group *group,
> - struct device *prev_dev, int type)
> + struct device *prev_dev, int type,
> + unsigned long max_opt_dma_size)
> {
> struct iommu_domain *prev_dom;
> struct group_device *grp_dev;
> @@ -2977,6 +3001,9 @@ static int iommu_change_dev_def_domain(struct iommu_group *group,
>
> group->domain = group->default_domain;
>
> + if (max_opt_dma_size)
> + group->max_opt_dma_size = max_opt_dma_size;
Why not add a new function just do this? In this way, we do not need to modify
iommu_change_dev_def_domain() and patch 3/5 can be dropped.
> +
> /*
> * Release the mutex here because ops->probe_finalize() call-back of
> * some vendor IOMMU drivers calls arm_iommu_attach_device() which
> @@ -3003,6 +3030,7 @@ static int iommu_change_dev_def_domain(struct iommu_group *group,
>
> enum iommu_group_op {
> CHANGE_GROUP_TYPE,
> + CHANGE_DMA_OPT_SIZE,
> };
>
> static int __iommu_group_store_type(const char *buf, struct iommu_group *group,
> @@ -3031,7 +3059,24 @@ static int __iommu_group_store_type(const char *buf, struct iommu_group *group,
> return -EINVAL;
> }
>
> - return iommu_change_dev_def_domain(group, dev, type);
> + return iommu_change_dev_def_domain(group, dev, type, 0);
> +}
> +
> +static int __iommu_group_store_max_opt_dma_size(const char *buf,
> + struct iommu_group *group,
> + struct device *dev)
> +{
> + unsigned long val;
> +
> + if (kstrtoul(buf, 0, &val) || !val)
> + return -EINVAL;
> +
> + if (device_is_bound(dev)) {
> + pr_err_ratelimited("Device is still bound to driver\n");
> + return -EINVAL;
> + }
> +
> + return iommu_change_dev_def_domain(group, dev, __IOMMU_DOMAIN_SAME, val);
> }
>
> /*
> @@ -3108,6 +3153,9 @@ static ssize_t iommu_group_store_common(struct iommu_group *group,
> case CHANGE_GROUP_TYPE:
> ret = __iommu_group_store_type(buf, group, dev);
> break;
> + case CHANGE_DMA_OPT_SIZE:
> + ret = __iommu_group_store_max_opt_dma_size(buf, group, dev);
> + break;
> default:
> ret = -EINVAL;
> }
> @@ -3124,3 +3172,10 @@ static ssize_t iommu_group_store_type(struct iommu_group *group,
> {
> return iommu_group_store_common(group, CHANGE_GROUP_TYPE, buf, count);
> }
> +
> +static ssize_t iommu_group_store_max_opt_dma_size(struct iommu_group *group,
> + const char *buf,
> + size_t count)
> +{
> + return iommu_group_store_common(group, CHANGE_DMA_OPT_SIZE, buf, count);
> +}
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index b141cf71c7af..6915e68c40b7 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -430,6 +430,7 @@ extern int iommu_sva_unbind_gpasid(struct iommu_domain *domain,
> struct device *dev, ioasid_t pasid);
> extern struct iommu_domain *iommu_get_domain_for_dev(struct device *dev);
> extern struct iommu_domain *iommu_get_dma_domain(struct device *dev);
> +extern size_t iommu_group_get_max_opt_dma_size(struct iommu_group *group);
> extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
> phys_addr_t paddr, size_t size, int prot);
> extern int iommu_map_atomic(struct iommu_domain *domain, unsigned long iova,
> @@ -725,6 +726,11 @@ static inline struct iommu_domain *iommu_get_domain_for_dev(struct device *dev)
> return NULL;
> }
>
> +static inline size_t iommu_group_get_max_opt_dma_size(struct iommu_group *group)
> +{
> + return 0;
> +}
> +
> static inline int iommu_map(struct iommu_domain *domain, unsigned long iova,
> phys_addr_t paddr, size_t size, int prot)
> {
>
--
Regards,
Zhen Lei
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