From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH v5 02/12] iommu/vt-d: Manage scalalble mode PASID tables
Date: Wed, 5 Dec 2018 16:50:12 +0100
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To: Lu Baolu <baolu.lu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: "Tian, Kevin" <kevin.tian-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, "Raj, Ashok" <ashok.raj-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Jean-Philippe Brucker <jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org>, "Kumar,
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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