Linux-ARM-Kernel Archive on lore.kernel.org
 help / color / Atom feed
From: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <Mark.Rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"jacob.jun.pan@linux.intel.com" <jacob.jun.pan@linux.intel.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	Will Deacon <Will.Deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"eric.auger@redhat.com" <eric.auger@redhat.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	Robin Murphy <Robin.Murphy@arm.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 6/8] iommu/arm-smmu-v3: Support auxiliary domains
Date: Fri, 5 Jul 2019 17:29:06 +0100
Message-ID: <7cad065e-5eba-bd22-5c1d-c55ad315ace0@arm.com> (raw)
In-Reply-To: <20190626175959.ubxvb2qn4taclact@willie-the-truck>

On 26/06/2019 18:59, Will Deacon wrote:
>> +static void arm_smmu_aux_detach_dev(struct iommu_domain *domain, struct device *dev)
>> +{
>> +	struct iommu_domain *parent_domain;
>> +	struct arm_smmu_domain *parent_smmu_domain;
>> +	struct arm_smmu_master *master = dev_to_master(dev);
>> +	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>> +
>> +	if (!arm_smmu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX))
>> +		return;
>> +
>> +	parent_domain = iommu_get_domain_for_dev(dev);
>> +	if (!parent_domain)
>> +		return;
>> +	parent_smmu_domain = to_smmu_domain(parent_domain);
>> +
>> +	mutex_lock(&smmu_domain->init_mutex);
>> +	if (!smmu_domain->aux_nr_devs)
>> +		goto out_unlock;
>> +
>> +	if (!--smmu_domain->aux_nr_devs) {
>> +		arm_smmu_write_ctx_desc(parent_smmu_domain, smmu_domain->ssid,
>> +					NULL);
>> +		/*
>> +		 * TLB doesn't need invalidation since accesses from the device
>> +		 * can't use this domain's ASID once the CD is clear.
>> +		 *
>> +		 * Sadly that doesn't apply to ATCs, which are PASID tagged.
>> +		 * Invalidate all other devices as well, because even though
>> +		 * they weren't 'officially' attached to the auxiliary domain,
>> +		 * they could have formed ATC entries.
>> +		 */
>> +		arm_smmu_atc_inv_domain(smmu_domain, 0, 0);
> 
> I've been struggling to understand the locking here, since both
> arm_smmu_write_ctx_desc and arm_smmu_atc_inv_domain take and release the
> devices_lock for the domain. Is there not a problem with devices coming and
> going in-between the two calls?

Yes it's a problem. I suppose we could take the parent's init_mutex
(making sure that it protects detach_dev() as well.

First I need to figure out how to prevent the parent domain from
disappearing when auxiliary domains are attached, I seem to have forgotten
that. I think checking if AUXD is enabled in the device passed to
attach_dev() should be sufficient - that's what I do for SVA. But the
IOMMU API isn't quite ready to handle failure in iommu_detach_device() at
the moment. VFIO will free the domain even if it's still attached.

> 
>> +	} else {
>> +		struct arm_smmu_cmdq_ent cmd;
>> +
>> +		/* Invalidate only this device's ATC */
>> +		if (master->ats_enabled) {
>> +			arm_smmu_atc_inv_to_cmd(smmu_domain->ssid, 0, 0, &cmd);
>> +			arm_smmu_atc_inv_master(master, &cmd);
>> +		}
>> +	}
>> +out_unlock:
>> +	mutex_unlock(&smmu_domain->init_mutex);
>> +}
>> +
>> +static int arm_smmu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
>> +{
>> +	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>> +
>> +	return smmu_domain->ssid ?: -EINVAL;
>> +}
>> +
>>  static struct iommu_ops arm_smmu_ops = {
>>  	.capable		= arm_smmu_capable,
>>  	.domain_alloc		= arm_smmu_domain_alloc,
>> @@ -2539,6 +2772,13 @@ static struct iommu_ops arm_smmu_ops = {
>>  	.of_xlate		= arm_smmu_of_xlate,
>>  	.get_resv_regions	= arm_smmu_get_resv_regions,
>>  	.put_resv_regions	= arm_smmu_put_resv_regions,
>> +	.dev_has_feat		= arm_smmu_dev_has_feature,
>> +	.dev_feat_enabled	= arm_smmu_dev_feature_enabled,
>> +	.dev_enable_feat	= arm_smmu_dev_enable_feature,
>> +	.dev_disable_feat	= arm_smmu_dev_disable_feature,
> 
> Why can't we use the existing ->capable and ->dev_{get,set}_attr callbacks
> for this?

->capable isn't very useful because it applies to all SMMUs in the
system. The existing ->{get,set}_attr callbacks apply to an
iommu_domain. The main reason for doing it on endpoints was that it
would be tedious to keep track of capabilities when attaching and
detaching devices to a domain, especially for drivers that allow
multiple IOMMUs per domain [1]. There were more discussions, and in the
end Joerg proposed the current API for device attributes [2]

[1]
https://lore.kernel.org/lkml/aa1ff748-c2ec-acc0-f1d9-cdff2b131e58@linux.intel.com/
[2] https://lore.kernel.org/linux-iommu/20181207102926.GM16835@8bytes.org/

Thanks,
Jean

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-10 18:47 [PATCH 0/8] iommu: Add auxiliary domain and PASID support to Arm SMMUv3 Jean-Philippe Brucker
2019-06-10 18:47 ` [PATCH 1/8] iommu: Add I/O ASID allocator Jean-Philippe Brucker
2019-06-11  9:36   ` Jonathan Cameron
2019-06-11 14:35     ` Jean-Philippe Brucker
2019-06-11 18:13       ` Jacob Pan
2019-06-18 14:22         ` Jean-Philippe Brucker
2019-06-18 17:05           ` Jacob Pan
2019-06-19 14:26             ` Jean-Philippe Brucker
2019-06-11 12:26   ` Jacob Pan
2019-06-11 14:37     ` Jean-Philippe Brucker
2019-06-11 17:10       ` Jacob Pan
2019-06-12 11:30         ` Jean-Philippe Brucker
2019-06-10 18:47 ` [PATCH 2/8] dt-bindings: document PASID property for IOMMU masters Jean-Philippe Brucker
2019-07-08  7:58   ` Auger Eric
2019-06-10 18:47 ` [PATCH 3/8] iommu/arm-smmu-v3: Support platform SSID Jean-Philippe Brucker
2019-06-11  9:42   ` Jonathan Cameron
2019-06-11 14:35     ` Jean-Philippe Brucker
2019-06-18 18:08   ` Will Deacon
2019-06-19 11:53     ` Jean-Philippe Brucker
2019-07-08  7:58   ` Auger Eric
2019-06-10 18:47 ` [PATCH 4/8] iommu/arm-smmu-v3: Add support for Substream IDs Jean-Philippe Brucker
2019-06-11 10:19   ` Jonathan Cameron
2019-06-11 14:35     ` Jean-Philippe Brucker
2019-06-26 18:00   ` Will Deacon
2019-07-04  9:33     ` Jean-Philippe Brucker
2019-07-08 15:31   ` Auger Eric
2019-06-10 18:47 ` [PATCH 5/8] iommu/arm-smmu-v3: Add second level of context descriptor table Jean-Philippe Brucker
2019-06-11 10:24   ` Jonathan Cameron
2019-07-08 15:13   ` Auger Eric
2019-06-10 18:47 ` [PATCH 6/8] iommu/arm-smmu-v3: Support auxiliary domains Jean-Philippe Brucker
2019-06-26 17:59   ` Will Deacon
2019-07-05 16:29     ` Jean-Philippe Brucker [this message]
2019-06-10 18:47 ` [PATCH 7/8] iommu/arm-smmu-v3: Improve add_device() error handling Jean-Philippe Brucker
2019-07-08  7:58   ` Auger Eric
2019-06-10 18:47 ` [PATCH 8/8] iommu/arm-smmu-v3: Add support for PCI PASID Jean-Philippe Brucker
2019-06-11 10:45   ` Jonathan Cameron
2019-06-11 14:35     ` Jean-Philippe Brucker
2019-07-08  7:58   ` Auger Eric

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=7cad065e-5eba-bd22-5c1d-c55ad315ace0@arm.com \
    --to=jean-philippe.brucker@arm.com \
    --cc=Mark.Rutland@arm.com \
    --cc=Robin.Murphy@arm.com \
    --cc=Will.Deacon@arm.com \
    --cc=devicetree@vger.kernel.org \
    --cc=eric.auger@redhat.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jacob.jun.pan@linux.intel.com \
    --cc=joro@8bytes.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=robh+dt@kernel.org \
    --cc=will@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-ARM-Kernel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/0 linux-arm-kernel/git/0.git
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/1 linux-arm-kernel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-arm-kernel linux-arm-kernel/ https://lore.kernel.org/linux-arm-kernel \
		linux-arm-kernel@lists.infradead.org infradead-linux-arm-kernel@archiver.kernel.org
	public-inbox-index linux-arm-kernel


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-arm-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox