On Wed, Apr 08, 2015 at 01:45:19PM +1000, Alexey Kardashevskiy wrote:
> On 04/08/2015 12:01 PM, David Gibson wrote:
> >On Tue, Mar 31, 2015 at 04:28:39PM +1100, Alexey Kardashevskiy wrote:
> >>This enables multiple IOMMU groups in one VFIO container which means
> >>that multiple devices from different groups can share the same IOMMU
> >>table (or tables if DDW).
> >>
> >>This removes a group id from vfio_container_ioctl(). The kernel support
> >>is required for this; if the host kernel does not have the support,
> >>it will allow only one group per container. The PHB's "iommuid" property
> >>is ignored.
> >>
> >>This adds a sanity check that there is just one VFIO container per
> >>PHB address space.
> >>
> >>Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> >
> >[snip]
> >>diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >>index b012620..99e1900 100644
> >>--- a/hw/vfio/common.c
> >>+++ b/hw/vfio/common.c
> >>@@ -915,21 +915,23 @@ void vfio_put_base_device(VFIODevice *vbasedev)
> >> close(vbasedev->fd);
> >> }
> >>
> >>-static int vfio_container_do_ioctl(AddressSpace *as, int32_t groupid,
> >>+static int vfio_container_do_ioctl(AddressSpace *as,
> >> int req, void *param)
> >> {
> >>- VFIOGroup *group;
> >> VFIOContainer *container;
> >>- int ret = -1;
> >>+ int ret;
> >>+ VFIOAddressSpace *space;
> >>
> >>- group = vfio_get_group(groupid, as);
> >>- if (!group) {
> >>- error_report("vfio: group %d not registered", groupid);
> >>- return ret;
> >>- }
> >>+ space = vfio_get_address_space(as);
> >>+ container = QLIST_FIRST(&space->containers);
> >
> >So getting the container handle from the address space, rather than
> >the group id certainly makes more sense to me.
> >
> >>- container = group->container;
> >>- if (group->container) {
> >>+ if (!container) {
> >>+ error_report("vfio: container is not set");
> >>+ return -1;
> >>+ } else if (QLIST_NEXT(container, next)) {
> >>+ error_report("vfio: multiple containers per PHB are not
> >>supported");
> >>+ return -1;
> >
> >But if only one PHB per address space is possible, why is the
> >containers field a list in the first place?
>
>
> Historically the list was added in 3df3e0a5872 (the patch of yours
> :) ).
Heh.
> In theory we could implement spapr-pci-bridge (derived from pci-bridge) with
> isolation capability (i.e. its own LIOBN/DMA window), in this case there
> could be multiple containers per PHB address space. Other archs could want
> multiple containers for some other reason. It would help me a lot if you
> remembered why you kept the list at the first place :)
Ok, I've looked over the patch and it has jogged my memory a bit. So
the dumb answer is that it's because the per address-space list was
replacing a global list of containers
The more useful answer is that I think it was because I was
anticipating the possibility of working around the
one-group-per-container limit by allowing a single VFIOAddressSpace in
qemu to be backed by several containers, whose mappings would be kept
in sync from the userspace side by duplicating all mappings.
Anyway, I think that means the right way to implement this is by
duplicating the ioctl() across all the attached containers, rather
than picking just one.
> For now I guess I'll move the next patch ("vfio: spapr: Move SPAPR-related
> code to a separate file") before this one, do s/vfio_container_do_ioctl/
> vfio_spapr_container_do_ioctl/ and move it to hw/vfio/spapr.c. Makes
> sense?
That sounds fine, though I don't see that it really addresses the
question here.
>
>
> >>+ } else {
> >> ret = ioctl(container->fd, req, param);
> >> if (ret < 0) {
> >> error_report("vfio: failed to ioctl %d to container: ret=%d,
> >> %s",
> >>@@ -937,12 +939,10 @@ static int vfio_container_do_ioctl(AddressSpace *as,
> >>int32_t groupid,
> >> }
> >> }
> >>
> >>- vfio_put_group(group);
> >>-
> >> return ret;
> >> }
> >>
> >>-int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
> >>+int vfio_container_ioctl(AddressSpace *as,
> >> int req, void *param)
> >> {
> >> /* We allow only certain ioctls to the container */
> >>@@ -957,5 +957,5 @@ int vfio_container_ioctl(AddressSpace *as, int32_t
> >>groupid,
> >> return -1;
> >> }
> >>
> >>- return vfio_container_do_ioctl(as, groupid, req, param);
> >>+ return vfio_container_do_ioctl(as, req, param);
> >> }
> >>diff --git a/include/hw/vfio/vfio.h b/include/hw/vfio/vfio.h
> >>index 0b26cd8..76b5744 100644
> >>--- a/include/hw/vfio/vfio.h
> >>+++ b/include/hw/vfio/vfio.h
> >>@@ -3,7 +3,7 @@
> >>
> >> #include "qemu/typedefs.h"
> >>
> >>-extern int vfio_container_ioctl(AddressSpace *as, int32_t groupid,
> >>+extern int vfio_container_ioctl(AddressSpace *as,
> >> int req, void *param);
> >>
> >> #endif
> >
>
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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