> On 25. Sep 2019, at 06:22, Joerg Roedel <j...@8bytes.org> wrote:
>
> From: Joerg Roedel <jroe...@suse.de>
>
> The lock is not necessary because the device table does not
> contain shared state that needs protection. Locking is only
> needed on an individual entry basis, and that needs to
> happen on the iommu_dev_data level.
>
> Fixes: 92d420ec028d ("iommu/amd: Relax locking in dma_ops path")
> Signed-off-by: Joerg Roedel <jroe...@suse.de>
> ---
> drivers/iommu/amd_iommu.c | 23 ++++++-----------------
> 1 file changed, 6 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 042854bbc5bc..37a9c04fc728 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -70,7 +70,6 @@
> */
> #define AMD_IOMMU_PGSIZES ((~0xFFFUL) & ~(2ULL << 38))
>
> -static DEFINE_SPINLOCK(amd_iommu_devtable_lock);
> static DEFINE_SPINLOCK(pd_bitmap_lock);
>
> /* List of all available dev_data structures */
> @@ -2080,10 +2079,11 @@ static void do_detach(struct iommu_dev_data *dev_data)
> static int __attach_device(struct iommu_dev_data *dev_data,
> struct protection_domain *domain)
> {
> + unsigned long flags;
> int ret;
>
> /* lock domain */
> - spin_lock(&domain->lock);
> + spin_lock_irqsave(&domain->lock, flags);
>
> ret = -EBUSY;
> if (dev_data->domain != NULL)
> @@ -2097,7 +2097,7 @@ static int __attach_device(struct iommu_dev_data
> *dev_data,
> out_unlock:
>
> /* ready */
> - spin_unlock(&domain->lock);
> + spin_unlock_irqrestore(&domain->lock, flags);
>
> return ret;
> }
> @@ -2181,7 +2181,6 @@ static int attach_device(struct device *dev,
> {
> struct pci_dev *pdev;
> struct iommu_dev_data *dev_data;
> - unsigned long flags;
> int ret;
>
> dev_data = get_dev_data(dev);
> @@ -2209,9 +2208,7 @@ static int attach_device(struct device *dev,
> }
>
> skip_ats_check:
> - spin_lock_irqsave(&amd_iommu_devtable_lock, flags);
> ret = __attach_device(dev_data, domain);
> - spin_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
>
> /*
> * We might boot into a crash-kernel here. The crashed kernel
> @@ -2231,14 +2228,15 @@ static int attach_device(struct device *dev,
> static void __detach_device(struct iommu_dev_data *dev_data)
> {
> struct protection_domain *domain;
> + unsigned long flags;
>
> domain = dev_data->domain;
>
> - spin_lock(&domain->lock);
> + spin_lock_irqsave(&domain->lock, flags);
>
> do_detach(dev_data);
>
> - spin_unlock(&domain->lock);
> + spin_unlock_irqrestore(&domain->lock, flags);
> }
>
> /*
> @@ -2248,7 +2246,6 @@ static void detach_device(struct device *dev)
> {
> struct protection_domain *domain;
> struct iommu_dev_data *dev_data;
> - unsigned long flags;
>
> dev_data = get_dev_data(dev);
> domain = dev_data->domain;
> @@ -2262,10 +2259,7 @@ static void detach_device(struct device *dev)
> if (WARN_ON(!dev_data->domain))
> return;
>
> - /* lock device table */
> - spin_lock_irqsave(&amd_iommu_devtable_lock, flags);
> __detach_device(dev_data);
> - spin_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
>
> if (!dev_is_pci(dev))
> return;
> @@ -2910,9 +2904,6 @@ int __init amd_iommu_init_dma_ops(void)
> static void cleanup_domain(struct protection_domain *domain)
> {
> struct iommu_dev_data *entry;
> - unsigned long flags;
> -
> - spin_lock_irqsave(&amd_iommu_devtable_lock, flags);
>
> while (!list_empty(&domain->dev_list)) {
> entry = list_first_entry(&domain->dev_list,
> @@ -2920,8 +2911,6 @@ static void cleanup_domain(struct protection_domain
> *domain)
> BUG_ON(!entry->domain);
> __detach_device(entry);
> }
> -
> - spin_unlock_irqrestore(&amd_iommu_devtable_lock, flags);
> }
I'm guessing that it is free not to take the domain lock in cleanup_domain
since this is called when free-ing the domain. Right?
> static void protection_domain_free(struct protection_domain *domain)
> --
> 2.17.1
>
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Ralf Herbrich
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
