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Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used |
Date: |
Thu, 11 Oct 2012 15:44:10 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120911 Thunderbird/15.0.1 |
On 10/11/2012 03:44 PM, Michael S. Tsirkin wrote:
> On Thu, Oct 11, 2012 at 03:34:54PM +0200, Avi Kivity wrote:
>> On 10/11/2012 03:31 PM, Michael S. Tsirkin wrote:
>> > On Thu, Oct 11, 2012 at 03:27:03PM +0200, Avi Kivity wrote:
>> >> vhost doesn't support guest iommus yet, indicate it to the user
>> >> by gently depositing a core on their disk.
>> >>
>> >> Signed-off-by: Avi Kivity <address@hidden>
>> >
>> > Actually there is no problem. virtio bypasses an IOMMU,
>> > so vhost works fine by writing into guest memory directly.
>> >
>> > So I don't think we need this patch.
>>
>> The pci subsystem should set up the iommu so that it ignores virtio
>> devices. If it does, an emulated iommu will not reach vhost. If it
>> doesn't, then it will, and the assert() will alert us that we have a bug.
>
> You mean pci subsystem in the guest? I'm pretty sure that's not
> the case at the moment: iommu is on by default and applies
> to all devices unless you do something special.
> I see where you are coming from but it does
> not look right to break all existing guests.
No, qemu should configure virtio devices to bypass the iommu, even if it
is on.
> Also - I see no reason to single out vhost - I think same applies with
> any virtio device, since it doesn't use the DMA API.
True.
--
error compiling committee.c: too many arguments to function
- Re: [Qemu-devel] [RFC v1 3/7] memory: iommu support, (continued)
Re: [Qemu-devel] [RFC v1 3/7] memory: iommu support, Avi Kivity, 2012/10/11
[Qemu-devel] [RFC v1 5/7] i440fx: add an iommu, Avi Kivity, 2012/10/11
[Qemu-devel] [RFC v1 6/7] vfio: abort if an emulated iommu is used, Avi Kivity, 2012/10/11
[Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Avi Kivity, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Michael S. Tsirkin, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Avi Kivity, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Michael S. Tsirkin, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used,
Avi Kivity <=
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Michael S. Tsirkin, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Avi Kivity, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Michael S. Tsirkin, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Avi Kivity, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Alex Williamson, 2012/10/11
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Avi Kivity, 2012/10/15
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, liu ping fan, 2012/10/15
- Re: [Qemu-devel] [RFC v1 7/7] vhost: abort if an emulated iommu is used, Avi Kivity, 2012/10/15
Re: [Qemu-devel] [RFC v1 0/7] IOMMU support, Benjamin Herrenschmidt, 2012/10/11