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

[Lu Baolu]

Hi Joerg,

On 12/5/18 11:50 PM, Joerg Roedel wrote:
> 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.

Fair enough. I will fix this up in the next version.

Thank you for pointing this out.

Best regards,
Lu Baolu