From: Robin Murphy <robin.murphy@arm.com>
To: Baolu Lu <baolu.lu@linux.intel.com>, joro@8bytes.org
Cc: will@kernel.org, iommu@lists.linux.dev,
linux-arm-kernel@lists.infradead.org,
suravee.suthikulpanit@amd.com, vasant.hegde@amd.com,
mjrosato@linux.ibm.com, gerald.schaefer@linux.ibm.com,
schnelle@linux.ibm.com, linux-s390@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 04/15] iommu: Move bus setup to IOMMU device registration
Date: Wed, 6 Jul 2022 15:37:06 +0100 [thread overview]
Message-ID: <71835610-7798-5fbe-556a-fc44dc9e168b@arm.com> (raw)
In-Reply-To: <d6a8e85b-ab7d-f5c9-a8cb-79dd8e68c967@linux.intel.com>
On 2022-07-06 03:35, Baolu Lu wrote:
> On 2022/7/6 01:08, Robin Murphy wrote:
>> @@ -202,12 +210,32 @@ int iommu_device_register(struct iommu_device
>> *iommu,
>> spin_lock(&iommu_device_lock);
>> list_add_tail(&iommu->list, &iommu_device_list);
>> spin_unlock(&iommu_device_lock);
>> +
>> + for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
>> + struct bus_type *bus = iommu_buses[i];
>> + int err;
>> +
>> + if (bus->iommu_ops && bus->iommu_ops != ops) {
>> + err = -EBUSY;
>> + } else {
>> + bus->iommu_ops = ops;
>> + err = bus_iommu_probe(bus);
>> + }
>> + if (err) {
>> + iommu_device_unregister(iommu);
>> + return err;
>> + }
>> + }
>> +
>> return 0;
>> }
>> EXPORT_SYMBOL_GPL(iommu_device_register);
>
> With bus_set_iommu() retired, my understanding is that now we embrace
> the first-come-first-serve policy for bus->iommu_ops setting. This will
> lead to problem in different iommu_ops for different bus case. Did I
> overlook anything?
This is just formalising the de-facto situation that we don't actually
have any combination of drivers that could load on the same system
without already attempting to claim at least one bus in common. It's
also only temporary until the bus ops are removed completely and we
fully support multiple drivers coexisting, which only actually takes a
handful more patches - I've realised I could even bring that change
*ahead* of the big job of converting iommu_domain_alloc() (I'm not
convinced that the tree-wide flag-day patch for that I currently have in
the dev branch is really viable, nor that I've actually got the correct
device at some of the callsites), although whether it's worth the
potentially-surprising behaviour that might result I'm less sure.
If we already had systems where in-tree drivers successfully coexisted
on different buses then I'd have split this up and done something a bit
more involved to keep a vestigial bus_set_iommu() around until the final
bus ops removal, but since we don't, it seemed neatest to do all the
related work in one go.
Thanks,
Robin.
next prev parent reply other threads:[~2022-07-06 14:37 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-05 17:08 [PATCH v3 00/15] iommu: Retire bus_set_iommu() Robin Murphy
2022-07-05 17:08 ` [PATCH v3 01/15] iommu/vt-d: Handle race between registration and device probe Robin Murphy
2022-07-06 1:39 ` Baolu Lu
2022-07-07 6:51 ` Tian, Kevin
2022-07-08 7:52 ` Baolu Lu
2022-07-15 12:37 ` Robin Murphy
2022-07-19 0:06 ` Lu Baolu
2022-07-05 17:08 ` [PATCH v3 02/15] iommu/amd: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 03/15] iommu: Always register bus notifiers Robin Murphy
2022-07-06 1:53 ` Baolu Lu
2022-07-06 13:43 ` Robin Murphy
2022-07-07 0:20 ` Baolu Lu
2022-07-07 6:34 ` Tian, Kevin
2022-07-07 9:38 ` Robin Murphy
2022-07-07 6:31 ` Tian, Kevin
2022-07-07 9:58 ` Robin Murphy
2022-07-08 5:50 ` Tian, Kevin
2022-07-05 17:08 ` [PATCH v3 04/15] iommu: Move bus setup to IOMMU device registration Robin Murphy
2022-07-06 2:35 ` Baolu Lu
2022-07-06 14:37 ` Robin Murphy [this message]
2022-07-07 1:19 ` Baolu Lu
2022-07-07 6:51 ` Tian, Kevin
2022-07-07 10:58 ` Robin Murphy
2022-07-08 5:52 ` Tian, Kevin
2022-07-05 17:08 ` [PATCH v3 05/15] iommu/amd: Clean up bus_set_iommu() Robin Murphy
2022-07-05 17:08 ` [PATCH v3 06/15] iommu/arm-smmu: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 07/15] iommu/arm-smmu-v3: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 08/15] iommu/dart: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 09/15] iommu/exynos: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 10/15] iommu/ipmmu-vmsa: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 11/15] iommu/mtk: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 12/15] iommu/omap: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 13/15] iommu/tegra-smmu: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 14/15] iommu/virtio: " Robin Murphy
2022-07-05 17:08 ` [PATCH v3 15/15] iommu: " Robin Murphy
2022-07-07 7:45 ` Tian, Kevin
2022-07-07 12:49 ` Matthew Rosato
2022-07-07 12:54 ` Matthew Rosato
2022-07-07 14:58 ` Robin Murphy
2022-07-07 16:42 ` Matthew Rosato
2022-07-08 8:14 ` [PATCH] iommu/s390: fail probe for non-pci device Niklas Schnelle
2022-07-08 8:17 ` [PATCH v3 00/15] iommu: Retire bus_set_iommu() Niklas Schnelle
2022-07-15 13:12 ` Robin Murphy
2022-07-21 7:17 ` Tian, Kevin
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