linux-kernel - Re: [PATCH 3/5] iommu/dart: Set DMA domain for locked DARTs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c4c54243-d25b-45d7-97d5-837d02cfa2dd@arm.com>
Date: Tue, 11 Feb 2025 20:37:08 +0000
From: Robin Murphy <robin.murphy@....com>
To: Alyssa Rosenzweig <alyssa@...enzweig.io>
Cc: Sven Peter <sven@...npeter.dev>, Janne Grunau <j@...nau.net>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
 iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] iommu/dart: Set DMA domain for locked DARTs

On 2025-02-11 6:40 pm, Alyssa Rosenzweig wrote:
> Hi Robin,
> 
>>> This is required.
>>
>> Now that we can, I'd really rather do this properly and not offer an
>> identity domain in the first place when it's not available.
> 
> I'm reading through iommu.c but I don't see a way to avoid offering an
> identity domain without the DMA override here, just reading through the
> logic of iommu_get_default_domain_type. Could you point me to what you
> have in mind?

Since we finished cleaning up the domain allocation paths, it's finally 
safe to have per-instance ops, so you can mix and match some with an 
identity domain and some without, as s390 will be doing[1].

Cheers,
Robin.

[1] 
https://lore.kernel.org/linux-iommu/20250207205335.473946-5-mjrosato@linux.ibm.com/

> Thanks,
> Alyssa
> 
>>> --- a/drivers/iommu/apple-dart.c
>>> +++ b/drivers/iommu/apple-dart.c
>>> @@ -941,6 +941,8 @@ static int apple_dart_def_domain_type(struct device *dev)
>>>    		return IOMMU_DOMAIN_IDENTITY;
>>>    	if (!cfg->stream_maps[0].dart->supports_bypass)
>>>    		return IOMMU_DOMAIN_DMA;
>>> +	if (cfg->stream_maps[0].dart->locked)
>>> +		return IOMMU_DOMAIN_DMA;
>>>    	return 0;
>>>    }
>>>
>>