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Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CA
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest |
Date: |
Fri, 20 Jan 2017 17:30:24 +0800 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Fri, Jan 20, 2017 at 09:20:01AM +0000, Tian, Kevin wrote:
> > From: Peter Xu [mailto:address@hidden
> > Sent: Friday, January 20, 2017 5:12 PM
> >
> > On Fri, Jan 20, 2017 at 08:59:01AM +0000, Tian, Kevin wrote:
> >
> > [...]
> >
> > > > > Also for hot-add
> > > > > device path, some check of caching mode is required. If not set,
> > > > > should we fail hot-add operation? I don't think we have such physical
> > > > > platform with some devices behind IOMMU while others not.
> > > >
> > > > Could you explain in what case will we fail a hot plug?
> > > >
> > >
> > > user enables intel-iommu, but don't set caching mode.
> > >
> > > Then later user hot-add a PCI device to the VM. Guest will assume
> > > newly assigned device also behind the default vIOMMU, and thus
> > > needs to setup IOVA mappings, which is then broken...
> >
> > Is the newly added device a vfio-pci device? If so, we should hit
> > this and VM will stops to work:
> >
> > if (!s->cache_mode_enabled && new & IOMMU_NOTIFIER_MAP) {
> > error_report("We need to set cache_mode=1 for intel-iommu to enable
> > "
> > "device assignment with IOMMU protection.");
> > exit(1);
> > }
>
> sorry I didn't found this code. In which code path is it hit?
It's in patch 14/14 of this series.
>
> >
> > I admit this is not user-friendly, and a better way may be that we
> > disallow the hot-plug in that case, telling the user about the error,
> > rather than crashing the VM. But, I think that can be a patch outside
> > this series, considering (again) that this only affects advanced
> > users.
> >
>
> Crashing VM is bad.... but anyway, I'll leave maintainer to decide
> whether they'd like it fixed now or later. :-)
Sure. Thanks,
-- peterx
- [Qemu-devel] [PATCH RFC v3 00/14] VT-d: vfio enablement and misc enhances, Peter Xu, 2017/01/12
- [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest, Peter Xu, 2017/01/12
- Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest, Tian, Kevin, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest, Peter Xu, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest, Tian, Kevin, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest, Peter Xu, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest, Tian, Kevin, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest,
Peter Xu <=
Re: [Qemu-devel] [PATCH RFC v3 01/14] IOMMU: add option to enable VTD_CAP_CM to vIOMMU capility exposoed to guest, Eric Blake, 2017/01/20
[Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Peter Xu, 2017/01/12
- Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Tian, Kevin, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Peter Xu, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Tian, Kevin, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Peter Xu, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Tian, Kevin, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Peter Xu, 2017/01/20
- Re: [Qemu-devel] [PATCH RFC v3 02/14] intel_iommu: simplify irq region translation, Tian, Kevin, 2017/01/21