From: Pierre Morel <pmorel@linux.ibm.com>
To: Mauricio Tavares <raubvogel@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-s390@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] s390: protvirt: virtio: Refuse device without IOMMU
Date: Fri, 12 Jun 2020 17:15:07 +0200 [thread overview]
Message-ID: <56545c29-c906-0020-6727-0e35c21741f5@linux.ibm.com> (raw)
In-Reply-To: <CAHEKYV6edAHyrW-VQtW5ufZkqpXbfd1sU9N4BqOktezdffHTsg@mail.gmail.com>
On 2020-06-12 15:45, Mauricio Tavares wrote:
> On Wed, Jun 10, 2020 at 12:32 PM Pierre Morel <pmorel@linux.ibm.com> wrote:
>>
>> Protected Virtualisation protects the memory of the guest and
>> do not allow a the host to access all of its memory.
>>
>> Let's refuse a VIRTIO device which does not use IOMMU
>> protected access.
>>
> Stupid questions:
not stupid at all. :)
>
> 1. Do all CPU families we care about (which are?) support IOMMU? Ex:
> would it recognize an ARM thingie with SMMU? [1]
In Message-ID: <6356ba7f-afab-75e1-05ff-4a22b88c610e@linux.ibm.com>
(as answer to Jason) I modified the patch and propose to take care of
this problem by using force_dma_unencrypted() inside virtio core instead
of a S390 specific test.
If we use force_dma_unencrypted(dev) to check if we must refuse a device
without the VIRTIO_F_IOMMU_PLATFORM feature, we are safe:
only architectures defining CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED will
have to define force_dma_unencrypted(dev), and they can choose what to
do by checking the architecture functionalities and/or the device.
> 2. Would it make sense to have some kind of
> yes-I-know-the-consequences-but-I-need-to-have-a-virtio-device-without-iommu-in-this-guest
> flag?
Yes, two ways:
Never refuse a device without VIRTIO_F_IOMMU_PLATFORM, by not defining
CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED or by always return 0 in
force_dma_unencrypted()
have force_dma_unencrypted() selectively answer by checking the device
and/or architecture state.
>
...snip...
>>
>
> [1] https://developer.arm.com/architectures/system-architectures/system-components/system-mmu-support
>
Regards,
Pierre
--
Pierre Morel
IBM Lab Boeblingen
prev parent reply other threads:[~2020-06-12 15:15 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 13:11 [PATCH] s390: protvirt: virtio: Refuse device without IOMMU Pierre Morel
2020-06-10 13:24 ` Cornelia Huck
2020-06-10 14:37 ` Pierre Morel
2020-06-10 14:53 ` Cornelia Huck
2020-06-10 15:27 ` Pierre Morel
2020-06-10 17:24 ` Halil Pasic
2020-06-11 3:10 ` Jason Wang
2020-06-12 9:21 ` Pierre Morel
2020-06-12 11:38 ` Pierre Morel
2020-06-15 3:01 ` Jason Wang
2020-06-15 10:37 ` Halil Pasic
2020-06-15 11:49 ` Pierre Morel
2020-06-15 11:50 ` Pierre Morel
2020-06-12 13:45 ` Mauricio Tavares
2020-06-12 15:15 ` Pierre Morel [this message]
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