RE: [PATCH 06/12] iommu/vt-d: Acquiring lock in domain ID allocation helpers

Tian, Kevin
2022-06-01T09:09:13Z

> From: Lu Baolu <baolu.lu@linux.intel.com>
> Sent: Friday, May 27, 2022 2:30 PM
>
> The iommu->lock is used to protect the per-IOMMU domain ID resource.
> Move the spinlock acquisition/release into the helpers where domain
> IDs are allocated and freed. The device_domain_lock is irrelevant to
> domain ID resources, remove its assertion as well.

while moving the lock you also replace spin_lock_irqsave() with spin_lock().
It'd be cleaner to just do movement here and then replace all _irqsave()
in patch 8.

>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/intel/iommu.c | 25 +++++++++----------------
> 1 file changed, 9 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 2d5f02b85de8..0da937ce0534 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1774,16 +1774,13 @@ static struct dmar_domain
> *alloc_domain(unsigned int type)
> return domain;
> }
>
> -/* Must be called with iommu->lock */
> static int domain_attach_iommu(struct dmar_domain *domain,
> struct intel_iommu *iommu)
> {
> unsigned long ndomains;
> - int num;
> -
> - assert_spin_locked(&device_domain_lock);
> - assert_spin_locked(&iommu->lock);
> + int num, ret = 0;
>
> + spin_lock(&iommu->lock);
> domain->iommu_refcnt[iommu->seq_id] += 1;
> if (domain->iommu_refcnt[iommu->seq_id] == 1) {
> ndomains = cap_ndoms(iommu->cap);
> @@ -1792,7 +1789,8 @@ static int domain_attach_iommu(struct
> dmar_domain *domain,
> if (num >= ndomains) {
> pr_err("%s: No free domain ids\n", iommu->name);
> domain->iommu_refcnt[iommu->seq_id] -= 1;
> - return -ENOSPC;
> + ret = -ENOSPC;
> + goto out_unlock;
> }
>
> set_bit(num, iommu->domain_ids);
> @@ -1801,7 +1799,9 @@ static int domain_attach_iommu(struct
> dmar_domain *domain,
> domain_update_iommu_cap(domain);
> }
>
> - return 0;
> +out_unlock:
> + spin_unlock(&iommu->lock);
> + return ret;
> }
>
> static void domain_detach_iommu(struct dmar_domain *domain,
> @@ -1809,9 +1809,7 @@ static void domain_detach_iommu(struct
> dmar_domain *domain,
> {
> int num;
>
> - assert_spin_locked(&device_domain_lock);
> - assert_spin_locked(&iommu->lock);
> -
> + spin_lock(&iommu->lock);
> domain->iommu_refcnt[iommu->seq_id] -= 1;
> if (domain->iommu_refcnt[iommu->seq_id] == 0) {
> num = domain->iommu_did[iommu->seq_id];
> @@ -1819,6 +1817,7 @@ static void domain_detach_iommu(struct
> dmar_domain *domain,
> domain_update_iommu_cap(domain);
> domain->iommu_did[iommu->seq_id] = 0;
> }
> + spin_unlock(&iommu->lock);
> }
>
> static inline int guestwidth_to_adjustwidth(int gaw)
> @@ -2471,9 +2470,7 @@ static int domain_add_dev_info(struct
> dmar_domain *domain, struct device *dev)
>
> spin_lock_irqsave(&device_domain_lock, flags);
> info->domain = domain;
> - spin_lock(&iommu->lock);
> ret = domain_attach_iommu(domain, iommu);
> - spin_unlock(&iommu->lock);
> if (ret) {
> spin_unlock_irqrestore(&device_domain_lock, flags);
> return ret;
> @@ -4158,7 +4155,6 @@ static void __dmar_remove_one_dev_info(struct
> device_domain_info *info)
> {
> struct dmar_domain *domain;
> struct intel_iommu *iommu;
> - unsigned long flags;
>
> assert_spin_locked(&device_domain_lock);
>
> @@ -4179,10 +4175,7 @@ static void __dmar_remove_one_dev_info(struct
> device_domain_info *info)
> }
>
> list_del(&info->link);
> -
> - spin_lock_irqsave(&iommu->lock, flags);
> domain_detach_iommu(domain, iommu);
> - spin_unlock_irqrestore(&iommu->lock, flags);
> }
>
> static void dmar_remove_one_dev_info(struct device *dev)
> --
> 2.25.1