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Date: Tue, 5 Sep 2023 10:26:01 +0530
From: Vasant Hegde <vasant.hegde@....com>
To: Tina Zhang <tina.zhang@...el.com>, Jason Gunthorpe <jgg@...pe.ca>,
Kevin Tian <kevin.tian@...el.com>,
Lu Baolu <baolu.lu@...ux.intel.com>
Cc: Michael Shavit <mshavit@...gle.com>, iommu@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/6] iommu: Support mm PASID 1:n with sva domains
On 9/5/2023 5:39 AM, Tina Zhang wrote:
> Each mm bound to devices gets a PASID and corresponding sva domains
> allocated in iommu_sva_bind_device(), which are referenced by iommu_mm
> field of the mm. The PASID is released in __mmdrop(), while a sva domain
> is released when no one is using it (the reference count is decremented
> in iommu_sva_unbind_device()). However, although sva domains and their
> PASID are separate objects such that their own life cycles could be
> handled independently, an enqcmd use case may require releasing the
> PASID in releasing the mm (i.e., once a PASID is allocated for a mm, it
> will be permanently used by the mm and won't be released until the end
> of mm) and only allows to drop the PASID after the sva domains are
> released. To this end, mmgrab() is called in iommu_sva_domain_alloc() to
> increment the mm reference count and mmdrop() is invoked in
> iommu_domain_free() to decrement the mm reference count.
>
> Since the required info of PASID and sva domains is kept in struct
> iommu_mm_data of a mm, use mm->iommu_mm field instead of the old pasid
> field in mm struct. The sva domain list is protected by iommu_sva_lock.
>
> Besides, this patch removes mm_pasid_init(), as with the introduced
> iommu_mm structure, initializing mm pasid in mm_init() is unnecessary.
>
> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Signed-off-by: Tina Zhang <tina.zhang@...el.com>
Looks good to me.
Reviewed-by: Vasant Hegde <vasant.hegde@....com>
-Vasant
> ---
>
> Changes in v3:
> - Add a comment describing domain->next.
> - Update the commit message.
>
> drivers/iommu/iommu-sva.c | 38 +++++++++++++++++++++++++-------------
> include/linux/iommu.h | 14 +++++++-------
> kernel/fork.c | 1 -
> 3 files changed, 32 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index 0a4a1ed40814..e7e3aeaa7055 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -15,6 +15,7 @@ static DEFINE_IDA(iommu_global_pasid_ida);
> /* Allocate a PASID for the mm within range (inclusive) */
> static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
> {
> + struct iommu_mm_data *iommu_mm;
> int ret = 0;
>
> if (min == IOMMU_PASID_INVALID ||
> @@ -33,11 +34,22 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t ma
> goto out;
> }
>
> + iommu_mm = kzalloc(sizeof(struct iommu_mm_data), GFP_KERNEL);
> + if (!iommu_mm) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
> - if (ret < 0)
> + if (ret < 0) {
> + kfree(iommu_mm);
> goto out;
> + }
> +
> + iommu_mm->pasid = ret;
> + INIT_LIST_HEAD(&iommu_mm->sva_domains);
> + mm->iommu_mm = iommu_mm;
>
> - mm->pasid = ret;
> ret = 0;
> out:
> mutex_unlock(&iommu_sva_lock);
> @@ -82,16 +94,12 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
>
> mutex_lock(&iommu_sva_lock);
> /* Search for an existing domain. */
> - domain = iommu_get_domain_for_dev_pasid(dev, mm_get_pasid(mm),
> - IOMMU_DOMAIN_SVA);
> - if (IS_ERR(domain)) {
> - ret = PTR_ERR(domain);
> - goto out_unlock;
> - }
> -
> - if (domain) {
> - domain->users++;
> - goto out;
> + list_for_each_entry(domain, &mm->iommu_mm->sva_domains, next) {
> + ret = iommu_attach_device_pasid(domain, dev, mm_get_pasid(mm));
> + if (!ret) {
> + domain->users++;
> + goto out;
> + }
> }
>
> /* Allocate a new domain and set it on device pasid. */
> @@ -105,6 +113,8 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
> if (ret)
> goto out_free_domain;
> domain->users = 1;
> + list_add(&domain->next, &mm->iommu_mm->sva_domains);
> +
> out:
> mutex_unlock(&iommu_sva_lock);
> handle->dev = dev;
> @@ -137,8 +147,9 @@ void iommu_sva_unbind_device(struct iommu_sva *handle)
> struct device *dev = handle->dev;
>
> mutex_lock(&iommu_sva_lock);
> + iommu_detach_device_pasid(domain, dev, pasid);
> if (--domain->users == 0) {
> - iommu_detach_device_pasid(domain, dev, pasid);
> + list_del(&domain->next);
> iommu_domain_free(domain);
> }
> mutex_unlock(&iommu_sva_lock);
> @@ -218,4 +229,5 @@ void mm_pasid_drop(struct mm_struct *mm)
> return;
>
> ida_free(&iommu_global_pasid_ida, mm_get_pasid(mm));
> + kfree(mm->iommu_mm);
> }
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 937f3abc26f2..95ada53f24ec 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -109,6 +109,11 @@ struct iommu_domain {
> struct { /* IOMMU_DOMAIN_SVA */
> struct mm_struct *mm;
> int users;
> + /*
> + * Next iommu_domain in mm->iommu_mm->sva-domains list
> + * protected by iommu_sva_lock.
> + */
> + struct list_head next;
> };
> };
> };
> @@ -1177,17 +1182,13 @@ static inline bool tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream
> }
>
> #ifdef CONFIG_IOMMU_SVA
> -static inline void mm_pasid_init(struct mm_struct *mm)
> -{
> - mm->pasid = IOMMU_PASID_INVALID;
> -}
> static inline bool mm_valid_pasid(struct mm_struct *mm)
> {
> - return mm->pasid != IOMMU_PASID_INVALID;
> + return mm->iommu_mm ? true : false;
> }
> static inline u32 mm_get_pasid(struct mm_struct *mm)
> {
> - return mm->pasid;
> + return mm->iommu_mm ? mm->iommu_mm->pasid : IOMMU_PASID_INVALID;
> }
> static inline u32 mm_get_enqcmd_pasid(struct mm_struct *mm)
> {
> @@ -1213,7 +1214,6 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> {
> return IOMMU_PASID_INVALID;
> }
> -static inline void mm_pasid_init(struct mm_struct *mm) {}
> static inline bool mm_valid_pasid(struct mm_struct *mm) { return false; }
> static inline u32 mm_get_pasid(struct mm_struct *mm)
> {
> diff --git a/kernel/fork.c b/kernel/fork.c
> index d2e12b6d2b18..f06392dd1ca8 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1274,7 +1274,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
> mm_init_cpumask(mm);
> mm_init_aio(mm);
> mm_init_owner(mm, p);
> - mm_pasid_init(mm);
> RCU_INIT_POINTER(mm->exe_file, NULL);
> mmu_notifier_subscriptions_init(mm);
> init_tlb_flush_pending(mm);
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