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Re: [PATCH v5 11/11] vfio: Disable only uncoordinated discards for VFIO_
From: |
Alex Williamson |
Subject: |
Re: [PATCH v5 11/11] vfio: Disable only uncoordinated discards for VFIO_TYPE1 iommus |
Date: |
Tue, 16 Feb 2021 12:03:19 -0700 |
On Thu, 21 Jan 2021 12:05:40 +0100
David Hildenbrand <david@redhat.com> wrote:
> We support coordinated discarding of RAM using the RamDiscardMgr 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 RamDiscardMgr 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).
>
> 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>
> ---
> hw/vfio/common.c | 63 +++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 51 insertions(+), 12 deletions(-)
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 15ecd05a4b..d879b8ab92 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -135,6 +135,27 @@ 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 RamDiscardMgr. */
> + return ram_block_uncoordinated_discard_disable(state);
> + default:
> + /*
> + * VFIO_SPAPR_TCE_IOMMU most probably works just fine with
> + * RamDiscardMgr, 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 RamDiscardMgr. We would have to special-case sections
> + * with a RamDiscardMgr.
> + */
> + return ram_block_discard_disable(state);
> + }
> +}
> +
> int vfio_set_irq_signaling(VFIODevice *vbasedev, int index, int subindex,
> int action, int fd, Error **errp)
> {
> @@ -1979,15 +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 RamDiscardMgr
> + * 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);
> @@ -2025,6 +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:
> @@ -2072,7 +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;
> @@ -2084,7 +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;
> }
> }
>
> @@ -2097,7 +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) {
> @@ -2112,7 +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 */
> @@ -2153,6 +2190,9 @@ listener_release_exit:
> 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);
>
> @@ -2160,7 +2200,6 @@ close_fd_exit:
> close(fd);
>
> put_space_exit:
> - ram_block_discard_disable(false);
> vfio_put_address_space(space);
>
> return ret;
> @@ -2282,7 +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);
> @@ -2336,7 +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);
> }
> }
>
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