Re: [Qemu-devel] [RFC PATCH 09/20] Memory: introduce iommu_ops->record_device

Liu, Yi L
2017-05-19T09:52:13Z

On Fri, May 19, 2017 at 09:07:49AM +0000, Tian, Kevin wrote:
> > From: Liu, Yi L [mailto:yi.l.liu@linux.intel.com]
> > Sent: Friday, May 19, 2017 1:24 PM
> >
> > Hi Alex,
> >
> > What's your opinion with Tianyu's question? Is it accepatable
> > to use VFIO API in intel_iommu emulator?
>
> Did you actually need such translation at all? SID should be
> filled by kernel IOMMU driver based on which device is
> requested with invalidation request, regardless of which
> guest SID is used in user space. Qemu only needs to know
> which fd corresponds to guest SID, and then initiates an
> invalidation request on that fd?

Kevin,

It actually depends on the svm binding behavior we expect in host
IOMMU driver side. If we want to have the binding per-device, this
translation is needed in Qemu either in VFIO or intel_iommu emulator.
So that the host SID could be used as a device selector when looping
devices in a group.

If we can use VFIO API directly, we also may trigger the svm bind/qi
propagation straightforwardly instead of using notifier.

Thanks,
Yi L

> >
> > Thanks,
> > Yi L
> > On Fri, Apr 28, 2017 at 02:46:16PM +0800, Lan Tianyu wrote:
> > > On 2017年04月26日 18:06, Liu, Yi L wrote:
> > > > With vIOMMU exposed to guest, vIOMMU emulator needs to do
> > translation
> > > > between host and guest. e.g. a device-selective TLB flush, vIOMMU
> > > > emulator needs to replace guest SID with host SID so that to limit
> > > > the invalidation. This patch introduces a new callback
> > > > iommu_ops->record_device() to notify vIOMMU emulator to record
> > necessary
> > > > information about the assigned device.
> > >
> > > This patch is to prepare to translate guest sbdf to host sbdf.
> > >
> > > Alex:
> > > Could we add a new vfio API to do such translation? This will be more
> > > straight forward than storing host sbdf in the vIOMMU device model.
> > >
> > > >
> > > > Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> > > > ---
> > > > include/exec/memory.h | 11 +++++++++++
> > > > memory.c | 12 ++++++++++++
> > > > 2 files changed, 23 insertions(+)
> > > >
> > > > diff --git a/include/exec/memory.h b/include/exec/memory.h
> > > > index 7bd13ab..49087ef 100644
> > > > --- a/include/exec/memory.h
> > > > +++ b/include/exec/memory.h
> > > > @@ -203,6 +203,8 @@ struct MemoryRegionIOMMUOps {
> > > > IOMMUNotifierFlag new_flags);
> > > > /* Set this up to provide customized IOMMU replay function */
> > > > void (*replay)(MemoryRegion *iommu, IOMMUNotifier *notifier);
> > > > + void (*record_device)(MemoryRegion *iommu,
> > > > + void *device_info);
> > > > };
> > > >
> > > > typedef struct CoalescedMemoryRange CoalescedMemoryRange;
> > > > @@ -708,6 +710,15 @@ void
> > memory_region_notify_iommu(MemoryRegion *mr,
> > > > void memory_region_notify_one(IOMMUNotifier *notifier,
> > > > IOMMUTLBEntry *entry);
> > > >
> > > > +/*
> > > > + * memory_region_notify_device_record: notify IOMMU to record
> > assign
> > > > + * device.
> > > > + * @mr: the memory region to notify
> > > > + * @ device_info: device information
> > > > + */
> > > > +void memory_region_notify_device_record(MemoryRegion *mr,
> > > > + void *info);
> > > > +
> > > > /**
> > > > * memory_region_register_iommu_notifier: register a notifier for
> > changes to
> > > > * IOMMU translation entries.
> > > > diff --git a/memory.c b/memory.c
> > > > index 0728e62..45ef069 100644
> > > > --- a/memory.c
> > > > +++ b/memory.c
> > > > @@ -1600,6 +1600,18 @@ static void
> > memory_region_update_iommu_notify_flags(MemoryRegion *mr)
> > > > mr->iommu_notify_flags = flags;
> > > > }
> > > >
> > > > +void memory_region_notify_device_record(MemoryRegion *mr,
> > > > + void *info)
> > > > +{
> > > > + assert(memory_region_is_iommu(mr));
> > > > +
> > > > + if (mr->iommu_ops->record_device) {
> > > > + mr->iommu_ops->record_device(mr, info);
> > > > + }
> > > > +
> > > > + return;
> > > > +}
> > > > +
> > > > void memory_region_register_iommu_notifier(MemoryRegion *mr,
> > > > IOMMUNotifier *n)
> > > > {
> > > >
> > >
> > >