On 05/08/2018 12:57 PM, Alex Williamson wrote:
On Mon, 7 May 2018 18:23:46 -0500
Bjorn Helgaas <helg...@kernel.org> wrote:
On Mon, Apr 23, 2018 at 05:30:32PM -0600, Logan Gunthorpe wrote:
Hi Everyone,
Here's v4 of our series to introduce P2P based copy offload to NVMe
fabrics. This version has been rebased onto v4.17-rc2. A git repo
is here:
https://github.com/sbates130272/linux-p2pmem pci-p2p-v4
...
Logan Gunthorpe (14):
PCI/P2PDMA: Support peer-to-peer memory
PCI/P2PDMA: Add sysfs group to display p2pmem stats
PCI/P2PDMA: Add PCI p2pmem dma mappings to adjust the bus offset
PCI/P2PDMA: Clear ACS P2P flags for all devices behind switches
docs-rst: Add a new directory for PCI documentation
PCI/P2PDMA: Add P2P DMA driver writer's documentation
block: Introduce PCI P2P flags for request and request queue
IB/core: Ensure we map P2P memory correctly in
rdma_rw_ctx_[init|destroy]()
nvme-pci: Use PCI p2pmem subsystem to manage the CMB
nvme-pci: Add support for P2P memory in requests
nvme-pci: Add a quirk for a pseudo CMB
nvmet: Introduce helper functions to allocate and free request SGLs
nvmet-rdma: Use new SGL alloc/free helper for requests
nvmet: Optionally use PCI P2P memory
Documentation/ABI/testing/sysfs-bus-pci | 25 +
Documentation/PCI/index.rst | 14 +
Documentation/driver-api/index.rst | 2 +-
Documentation/driver-api/pci/index.rst | 20 +
Documentation/driver-api/pci/p2pdma.rst | 166 ++++++
Documentation/driver-api/{ => pci}/pci.rst | 0
Documentation/index.rst | 3 +-
block/blk-core.c | 3 +
drivers/infiniband/core/rw.c | 13 +-
drivers/nvme/host/core.c | 4 +
drivers/nvme/host/nvme.h | 8 +
drivers/nvme/host/pci.c | 118 +++--
drivers/nvme/target/configfs.c | 67 +++
drivers/nvme/target/core.c | 143 ++++-
drivers/nvme/target/io-cmd.c | 3 +
drivers/nvme/target/nvmet.h | 15 +
drivers/nvme/target/rdma.c | 22 +-
drivers/pci/Kconfig | 26 +
drivers/pci/Makefile | 1 +
drivers/pci/p2pdma.c | 814 +++++++++++++++++++++++++++++
drivers/pci/pci.c | 6 +
include/linux/blk_types.h | 18 +-
include/linux/blkdev.h | 3 +
include/linux/memremap.h | 19 +
include/linux/pci-p2pdma.h | 118 +++++
include/linux/pci.h | 4 +
26 files changed, 1579 insertions(+), 56 deletions(-)
create mode 100644 Documentation/PCI/index.rst
create mode 100644 Documentation/driver-api/pci/index.rst
create mode 100644 Documentation/driver-api/pci/p2pdma.rst
rename Documentation/driver-api/{ => pci}/pci.rst (100%)
create mode 100644 drivers/pci/p2pdma.c
create mode 100644 include/linux/pci-p2pdma.h
How do you envison merging this? There's a big chunk in drivers/pci, but
really no opportunity for conflicts there, and there's significant stuff in
block and nvme that I don't really want to merge.
If Alex is OK with the ACS situation, I can ack the PCI parts and you could
merge it elsewhere?
AIUI from previously questioning this, the change is hidden behind a
build-time config option and only custom kernels or distros optimized
for this sort of support would enable that build option. I'm more than
a little dubious though that we're not going to have a wave of distros
enabling this only to get user complaints that they can no longer make
effective use of their devices for assignment due to the resulting span
of the IOMMU groups, nor is there any sort of compromise, configure
the kernel for p2p or device assignment, not both. Is this really such
a unique feature that distro users aren't going to be asking for both
features? Thanks,
Alex
At least 1/2 the cases presented to me by existing customers want it in a
tunable kernel,
and tunable btwn two points, if the hw allows it to be 'contained' in that
manner, which
a (layer of) switch(ing) provides.
To me, that means a kernel cmdline parameter to _enable_, and another sysfs
(configfs? ... i'm not a configfs afficionato to say which is best),
method to make two points p2p dma capable.
Worse case, the whole system is one large IOMMU group (current mindset of this
static or run-time config option),
or best case (over time, more hw), a secure set of the primary system with
p2p-enabled sections, that are deemed 'safe' or 'self-inflicting-unsecure',
the latter the case of today's VM with an assigned device -- can scribble all
over the VM, but no other VM and not the host/HV.
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