Hi Will,
On 11/19/20 4:53 PM, Will Deacon wrote:
On Thu, Nov 19, 2020 at 10:18:05AM +0800, Lu Baolu wrote:
The original author of this patch series has left Intel. I am now the
backup.
Ok, thanks for letting me know.
On 11/18/20 9:51 PM, Will Deacon wrote:
On Fri, Sep 25, 2020 at 12:06:18PM -0700, Ashok Raj wrote:
From: Sai Praneeth Prakhya <[email protected]>
[...]
+free_new_domain:
+ iommu_domain_free(group->default_domain);
+ group->default_domain = prev_dom;
+ group->domain = prev_dom;i
Hmm. This seems to rely on all users of group->default_domain holding the
group->mutex. Have you confirmed that this is the case? There's a funny
use of iommu_group_get() in the exynos IOMMU driver at least.
Emm. This change happens within the area with group->mutex held. Or I
am not getting your point?
Yeah, sorry, I wasn't very clear. This code holds the group->mutex, and it
relies on _anybody_ else who wants to inspect group->default_domain also
holding that mutex, otherwise they could observe a transient domain pointer
which we free on the failure path here.
Clear to me now. Thanks for explanation. :-)
Changing default domain through sysfs requires the users to ubind any
driver from the devices in the group. There's a check code and return
failure if this requirement doesn't meet.
So we only need to consider the device release path. device_lock(dev) is
used in this patch to guarantee that no device release happens at the
same time.
My question is whether or not there is code that inspects
group->default_domain without group->mutex held? The exynos case doesn't
obviously hold it, and I'd like to make sure that there aren't others that
we need to worry about.
I searched the code. The exynos is the only case that inspects
group->default_domain without holding the mutex during run time. It's in
the device release path, so I think it's safe.
Does that make more sense?
Yes. Thanks!
Thanks,
Will
Best regards,
baolu
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