Re: [PATCH] iommu/arm-smmu-v3: Add default domain quirk for Arm Fast Models

From: Robin Murphy <robin.murphy@arm.com>
To: Will Deacon <will@kernel.org>
Cc: mark.rutland@arm.com, catalin.marinas@arm.com,
	andre.przywara@arm.com, iommu@lists.linux-foundation.org,
	maz@kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] iommu/arm-smmu-v3: Add default domain quirk for Arm Fast Models
Date: Tue, 29 Jun 2021 19:10:53 +0100	[thread overview]
Message-ID: <c644a7dd-c721-4cae-f2fa-0fae9b28ae9a@arm.com> (raw)
In-Reply-To: <20210629173440.GA7556@willie-the-truck>

On 2021-06-29 18:34, Will Deacon wrote:
> On Fri, Jun 18, 2021 at 05:24:49PM +0100, Robin Murphy wrote:
>> Arm Fast Models are still implementing legacy virtio-pci devices behind
>> the SMMU, which continue to be problematic as "real hardware" devices
>> (from the point of view of the simulated system) without the mitigating
>> VIRTIO_F_ACCESS_PLATFORM feature.
>>
>> Since we now have the ability to force passthrough on a device-specific
>> basis, let's use it to work around this particular oddity so that people
>> who just want to boot Linux on a model don't have to fiddle around with
>> things to avoid the SMMU getting in the way by default (and I don't have
>> to keep telling them which things...)
>>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>> ---
>>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
> 
> Any chance of getting the fastmodels updated instead? It feels like it
> has to happen *eventually*, and then there would be no need for this bodge.

If it's any consolation the JIRA ticket you raised in 2017 is still open...

Robin.

> 
> Will
> 
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> index 54b2f27b81d4..13cf16e8f45b 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -2649,6 +2649,20 @@ static int arm_smmu_dev_disable_feature(struct device *dev,
>>   	}
>>   }
>>   
>> +static int arm_smmu_def_domain_type(struct device *dev)
>> +{
>> +	if (dev_is_pci(dev)) {
>> +		struct pci_dev *pdev = to_pci_dev(dev);
>> +
>> +		/* Legacy virtio-block devices on Arm Fast Models */
>> +		if (pdev->vendor == 0x1af4 && pdev->device == 0x1001 &&
>> +		    pdev->subsystem_vendor == 0x00ff && pdev->subsystem_device == 0x0002)
>> +			return IOMMU_DOMAIN_IDENTITY;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   static struct iommu_ops arm_smmu_ops = {
>>   	.capable		= arm_smmu_capable,
>>   	.domain_alloc		= arm_smmu_domain_alloc,
>> @@ -2673,6 +2687,7 @@ static struct iommu_ops arm_smmu_ops = {
>>   	.sva_bind		= arm_smmu_sva_bind,
>>   	.sva_unbind		= arm_smmu_sva_unbind,
>>   	.sva_get_pasid		= arm_smmu_sva_get_pasid,
>> +	.def_domain_type	= arm_smmu_def_domain_type,
>>   	.pgsize_bitmap		= -1UL, /* Restricted during device attach */
>>   	.owner			= THIS_MODULE,
>>   };
>> -- 
>> 2.25.1
>>
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