Re: [PATCH v5 02/12] iommu/vt-d: Manage scalalble mode PASID tables

[Joerg Roedel]

On Tue, Dec 04, 2018 at 01:58:06PM +0800, Lu Baolu wrote:
> This function is called in an unsleepable context.
> 
> spin_lock(&lock)
> [...]
> if (pasid_table_is_necessary)
> 	allocate_pasid_table(dev)
> [...]
> spin_unlock(&lock)
> 
> We can move it out of the lock range.
> 
> How about
> 
> if (pasid_table_is_necessary)
> 	pasid_table = allocate_pasid_table(dev)
> 
> spin_lock(&lock)
> [...]
> if (pasid_table_is_necessary)
> 	set_up_pasid_table(pasid_table)
> [...]
> spin_unlock(&lock)

Hmm, so when the IOMMU is configured in scalable mode we can just
allocate a pasid-table for the device when we set it up, right?

Scalable mode is a boot-time decision, so we know for sure whether we
need a pasid-table on device-setup time. And the device-setup code it
preemptable, so I think it this allocation should be outside of any
spin-locked section.


	Joerg