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Message-Id: <1697677818-11371-1-git-send-email-si-wei.liu@oracle.com>
Date: Wed, 18 Oct 2023 18:10:13 -0700
From: Si-Wei Liu <si-wei.liu@...cle.com>
To: jasowang@...hat.com, mst@...hat.com, eperezma@...hat.com,
sgarzare@...hat.com, dtatulea@...dia.com
Cc: virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/4] vdpa: decouple reset of iotlb mapping from device reset
In order to reduce needlessly high setup and teardown cost
of iotlb mapping during live migration, it's crucial to
decouple the vhost-vdpa iotlb abstraction from the virtio
device life cycle, i.e. iotlb mappings should be left
intact across virtio device reset [1]. For it to work, the
on-chip IOMMU parent device could implement a separate
.reset_map() operation callback to restore 1:1 DMA mapping
without having to resort to the .reset() callback, the
latter of which is mainly used to reset virtio device state.
This new .reset_map() callback will be invoked only before
the vhost-vdpa driver is to be removed and detached from
the vdpa bus, such that other vdpa bus drivers, e.g.
virtio-vdpa, can start with 1:1 DMA mapping when they
are attached. For the context, those on-chip IOMMU parent
devices, create the 1:1 DMA mapping at vdpa device creation,
and they would implicitly destroy the 1:1 mapping when
the first .set_map or .dma_map callback is invoked.
This patchset is rebased on top of the latest vhost tree.
[1] Reducing vdpa migration downtime because of memory pin / maps
https://www.mail-archive.com/qemu-devel@nongnu.org/msg953755.html
---
v3:
- add .reset_map support to vdpa_sim
- introduce module parameter to provide bug-for-bug compatiblity with older
userspace
v2:
- improved commit message to clarify the intended csope of .reset_map API
- improved commit messages to clarify no breakage on older userspace
v1:
- rewrote commit messages to include more detailed description and background
- reword to vendor specific IOMMU implementation from on-chip IOMMU
- include parent device backend feautres to persistent iotlb precondition
- reimplement mlx5_vdpa patch on top of descriptor group series
RFC v3:
- fix missing return due to merge error in patch #4
RFC v2:
- rebased on top of the "[PATCH RFC v2 0/3] vdpa: dedicated descriptor table group" series:
https://lore.kernel.org/virtualization/1694248959-13369-1-git-send-email-si-wei.liu@oracle.com/
---
Si-Wei Liu (5):
vdpa: introduce .reset_map operation callback
vhost-vdpa: reset vendor specific mapping to initial state in .release
vhost-vdpa: introduce IOTLB_PERSIST backend feature bit
vdpa/mlx5: implement .reset_map driver op
vdpa_sim: implement .reset_map support
drivers/vdpa/mlx5/core/mlx5_vdpa.h | 1 +
drivers/vdpa/mlx5/core/mr.c | 17 +++++++++
drivers/vdpa/mlx5/net/mlx5_vnet.c | 26 ++++++++++++--
drivers/vdpa/vdpa_sim/vdpa_sim.c | 58 ++++++++++++++++++++++++------
drivers/vhost/vdpa.c | 31 ++++++++++++++++
include/linux/vdpa.h | 10 ++++++
include/uapi/linux/vhost_types.h | 2 ++
7 files changed, 132 insertions(+), 13 deletions(-)
--
2.39.3
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