From: Robin Murphy <robin.murphy@arm.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org, jon.grimm@amd.com,
linux-kernel@vger.kernel.org, vasant.hegde@amd.com
Subject: Re: [PATCH v2] iommu/amd: Set translation valid bit only when IO page tables are in used
Date: Fri, 20 May 2022 10:18:20 +0100 [thread overview]
Message-ID: <c10de7b0-ca73-e2a8-bdc5-1a3a9edd5f30@arm.com> (raw)
In-Reply-To: <YodYTZzSd9fZucLT@8bytes.org>
On 2022-05-20 09:58, Joerg Roedel wrote:
> On Fri, May 20, 2022 at 09:54:51AM +0100, Robin Murphy wrote:
>> The .def_domain type op already allows drivers to do exactly this sort of
>> override. You could also conditionally reject IOMMU_DOMAIN_PASSTHROUGH in
>> .domain_alloc for good measure, provided that (for now at least*) SNP is a
>> global thing rather than per-instance.
>
> Yeah, that could work. I am just not sure the IOMMU core behaves well in
> all situations when allocation IOMMU_DOMAIN_PASSTHROUGH suddenly starts
> to fail. I would feel better if this is checked and tested :)
Well, iommu_group_alloc_default_domain() has the fallback and is
currently the only place that __iommu_domain_alloc() can be called with
a type other than IOMMU_DOMAIN_UNMANAGED, so by inspection it should be
fine. However if iommu_get_def_domain_type() says the right thing then
neither sysfs nor automatic default domains should get as far as even
trying to allocate an identity domain anyway - note that that's already
what happens for untrusted external devices. But either way should be
easy enough to verify with a quick hack, too.
Cheers,
Robin.
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next prev parent reply other threads:[~2022-05-20 9:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-09 7:48 [PATCH v2] iommu/amd: Set translation valid bit only when IO page tables are in used Suravee Suthikulpanit via iommu
2022-05-13 13:07 ` Joerg Roedel
2022-05-16 12:27 ` Suravee Suthikulpanit via iommu
2022-05-20 8:09 ` Joerg Roedel
2022-05-20 8:54 ` Robin Murphy
2022-05-20 8:58 ` Joerg Roedel
2022-05-20 9:18 ` Robin Murphy [this message]
2022-05-26 3:29 ` Suravee Suthikulpanit via iommu
2022-06-07 8:00 ` Joerg Roedel
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