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Date:   Tue, 19 May 2020 00:09:53 -0700
From:   Jerry Snitselaar <jsnitsel@redhat.com>
To:     Joerg Roedel <jroedel@suse.de>
Cc:     Robin Murphy <robin.murphy@arm.com>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        Tom Murphy <murphyt7@tcd.ie>
Subject: Re: [PATCH] iommu: Implement deferred domain attachment
Message-ID: <20200519070953.dj46pvdqvqdglr4p@cantor>
Reply-To: Jerry Snitselaar <jsnitsel@redhat.com>
Mail-Followup-To: Joerg Roedel <jroedel@suse.de>,
        Robin Murphy <robin.murphy@arm.com>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        Tom Murphy <murphyt7@tcd.ie>
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 <20200515161400.GZ18353@8bytes.org>
 <e7bdcbf1-a713-618d-3e02-037f509a17e9@arm.com>
 <20200515182600.GJ8135@suse.de>
 <f5c6ec5b-06c6-42e6-b74d-71cf29b44b8d@arm.com>
 <20200518132656.GL8135@suse.de>
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On Mon May 18 20, Joerg Roedel wrote:
>On Fri, May 15, 2020 at 08:23:13PM +0100, Robin Murphy wrote:
>> But that's not what this is; this is (supposed to be) the exact same "don't
>> actually perform the attach yet" logic as before, just restricting it to
>> default domains in the one place that it actually needs to be, so as not to
>> fundamentally bugger up iommu_attach_device() in a way that prevents it from
>> working as expected at the correct point later.
>
>You are right, that is better. I tested it and it seems to work. Updated
>diff attached, with a minor cleanup included. Mind sending it as a
>proper patch I can send upstream?
>
>Thanks,
>
>	Joerg
>
>diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>index 7b375421afba..a9d02bc3ab5b 100644
>--- a/drivers/iommu/iommu.c
>+++ b/drivers/iommu/iommu.c
>@@ -693,6 +693,15 @@ static int iommu_group_create_direct_mappings(struct iommu_group *group,
> 	return ret;
> }
>
>+static bool iommu_is_attach_deferred(struct iommu_domain *domain,
>+				     struct device *dev)
>+{
>+	if (domain->ops->is_attach_deferred)
>+		return domain->ops->is_attach_deferred(domain, dev);
>+
>+	return false;
>+}
>+
> /**
>  * iommu_group_add_device - add a device to an iommu group
>  * @group: the group into which to add the device (reference should be held)
>@@ -705,6 +714,7 @@ int iommu_group_add_device(struct iommu_group *group, struct device *dev)
> {
> 	int ret, i = 0;
> 	struct group_device *device;
>+	struct iommu_domain *domain;
>
> 	device = kzalloc(sizeof(*device), GFP_KERNEL);
> 	if (!device)
>@@ -747,7 +757,8 @@ int iommu_group_add_device(struct iommu_group *group, struct device *dev)
>
> 	mutex_lock(&group->mutex);
> 	list_add_tail(&device->list, &group->devices);
>-	if (group->domain)
>+	domain = group->domain;
>+	if (domain  && !iommu_is_attach_deferred(domain, dev))
> 		ret = __iommu_attach_device(group->domain, dev);
> 	mutex_unlock(&group->mutex);
> 	if (ret)
>@@ -1653,9 +1664,6 @@ static int __iommu_attach_device(struct iommu_domain *domain,
> 				 struct device *dev)
> {
> 	int ret;
>-	if ((domain->ops->is_attach_deferred != NULL) &&
>-	    domain->ops->is_attach_deferred(domain, dev))
>-		return 0;
>
> 	if (unlikely(domain->ops->attach_dev == NULL))
> 		return -ENODEV;
>@@ -1727,8 +1735,7 @@ EXPORT_SYMBOL_GPL(iommu_sva_unbind_gpasid);
> static void __iommu_detach_device(struct iommu_domain *domain,
> 				  struct device *dev)
> {
>-	if ((domain->ops->is_attach_deferred != NULL) &&
>-	    domain->ops->is_attach_deferred(domain, dev))
>+	if (iommu_is_attach_deferred(domain, dev))
> 		return;
>
> 	if (unlikely(domain->ops->detach_dev == NULL))
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>

This worked for me as well.