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vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus
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We support coordinated discarding of RAM using the RamDiscardManager for
the VFIO_TYPE1 iommus. Let's unlock support for coordinated discards,
keeping uncoordinated discards (e.g., via virtio-balloon) disabled if
possible.

This unlocks virtio-mem + vfio on x86-64. Note that vfio used via "nvme://"
by the block layer has to be implemented/unlocked separately. For now,
virtio-mem only supports x86-64; we don't restrict RamDiscardManager to
x86-64, though: arm64 and s390x are supposed to work as well, and we'll
test once unlocking virtio-mem support. The spapr IOMMUs will need special
care, to be tackled later, e.g.., once supporting virtio-mem.

Note: The block size of a virtio-mem device has to be set to sane sizes,
depending on the maximum hotplug size - to not run out of vfio mappings.
The default virtio-mem block size is usually in the range of a couple of
MBs. The maximum number of mapping is 64k, shared with other users.
Assume you want to hotplug 256GB using virtio-mem - the block size would
have to be set to at least 8 MiB (resulting in 32768 separate mappings).

Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Auger Eric <eric.auger@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210413095531.25603-14-david@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
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@davidhildenbrand @ehabkost
davidhildenbrand authored and ehabkost committed Jul 8, 2021
1 parent bc072ed commit 53d1b5f
Showing 1 changed file with 53 additions and 12 deletions.
65 changes: 53 additions & 12 deletions hw/vfio/common.c
View file
Expand Up @@ -135,6 +135,29 @@ static const char *index_to_str(VFIODevice *vbasedev, int index)
}
}

static int vfio_ram_block_discard_disable(VFIOContainer *container, bool state)
{
switch (container->iommu_type) {
case VFIO_TYPE1v2_IOMMU:
case VFIO_TYPE1_IOMMU:
/*
* We support coordinated discarding of RAM via the RamDiscardManager.
*/
return ram_block_uncoordinated_discard_disable(state);
default:
/*
* VFIO_SPAPR_TCE_IOMMU most probably works just fine with
* RamDiscardManager, however, it is completely untested.
*
* VFIO_SPAPR_TCE_v2_IOMMU with "DMA memory preregistering" does
* completely the opposite of managing mapping/pinning dynamically as
* required by RamDiscardManager. We would have to special-case sections
* with a RamDiscardManager.
*/
return ram_block_discard_disable(state);
}
}

int vfio_set_irq_signaling(VFIODevice *vbasedev, int index, int subindex,
int action, int fd, Error **errp)
{
Expand Down Expand Up @@ -1977,15 +2000,25 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
* new memory, it will not yet set ram_block_discard_set_required() and
* therefore, neither stops us here or deals with the sudden memory
* consumption of inflated memory.
*
* We do support discarding of memory coordinated via the RamDiscardManager
* with some IOMMU types. vfio_ram_block_discard_disable() handles the
* details once we know which type of IOMMU we are using.
*/
ret = ram_block_discard_disable(true);
if (ret) {
error_setg_errno(errp, -ret, "Cannot set discarding of RAM broken");
return ret;
}

QLIST_FOREACH(container, &space->containers, next) {
if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
ret = vfio_ram_block_discard_disable(container, true);
if (ret) {
error_setg_errno(errp, -ret,
"Cannot set discarding of RAM broken");
if (ioctl(group->fd, VFIO_GROUP_UNSET_CONTAINER,
&container->fd)) {
error_report("vfio: error disconnecting group %d from"
" container", group->groupid);
}
return ret;
}
group->container = container;
QLIST_INSERT_HEAD(&container->group_list, group, container_next);
vfio_kvm_device_add_group(group);
Expand Down Expand Up @@ -2023,6 +2056,12 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
goto free_container_exit;
}

ret = vfio_ram_block_discard_disable(container, true);
if (ret) {
error_setg_errno(errp, -ret, "Cannot set discarding of RAM broken");
goto free_container_exit;
}

switch (container->iommu_type) {
case VFIO_TYPE1v2_IOMMU:
case VFIO_TYPE1_IOMMU:
Expand Down Expand Up @@ -2070,7 +2109,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
if (ret) {
error_setg_errno(errp, errno, "failed to enable container");
ret = -errno;
goto free_container_exit;
goto enable_discards_exit;
}
} else {
container->prereg_listener = vfio_prereg_listener;
Expand All @@ -2082,7 +2121,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
ret = -1;
error_propagate_prepend(errp, container->error,
"RAM memory listener initialization failed: ");
goto free_container_exit;
goto enable_discards_exit;
}
}

Expand All @@ -2095,7 +2134,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
if (v2) {
memory_listener_unregister(&container->prereg_listener);
}
goto free_container_exit;
goto enable_discards_exit;
}

if (v2) {
Expand All @@ -2110,7 +2149,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
if (ret) {
error_setg_errno(errp, -ret,
"failed to remove existing window");
goto free_container_exit;
goto enable_discards_exit;
}
} else {
/* The default table uses 4K pages */
Expand Down Expand Up @@ -2151,14 +2190,16 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
vfio_kvm_device_del_group(group);
vfio_listener_release(container);

enable_discards_exit:
vfio_ram_block_discard_disable(container, false);

free_container_exit:
g_free(container);

close_fd_exit:
close(fd);

put_space_exit:
ram_block_discard_disable(false);
vfio_put_address_space(space);

return ret;
Expand Down Expand Up @@ -2280,7 +2321,7 @@ void vfio_put_group(VFIOGroup *group)
}

if (!group->ram_block_discard_allowed) {
ram_block_discard_disable(false);
vfio_ram_block_discard_disable(group->container, false);
}
vfio_kvm_device_del_group(group);
vfio_disconnect_container(group);
Expand Down Expand Up @@ -2334,7 +2375,7 @@ int vfio_get_device(VFIOGroup *group, const char *name,

if (!group->ram_block_discard_allowed) {
group->ram_block_discard_allowed = true;
ram_block_discard_disable(false);
vfio_ram_block_discard_disable(group->container, false);
}
}

Expand Down

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