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The specification for VHOST_USER_ADD/REM_MEM_REG messages is unclear in several points, which has led to clients having incompatible implementations. This changes the specification to be more explicit about them: * VHOST_USER_ADD_MEM_REG is not specified as receiving a file descriptor, though it obviously does need to do so. All implementations agree on this one, fix the specification. * VHOST_USER_REM_MEM_REG is not specified as receiving a file descriptor either, and it also has no reason to do so. rust-vmm does not send file descriptors for removing a memory region (in agreement with the specification), libvhost-user and QEMU do (which is a bug), though libvhost-user doesn't actually make any use of it. Change the specification so that for compatibility QEMU's behaviour becomes legal, even if discouraged, but rust-vmm's behaviour becomes the explicitly recommended mode of operation. * VHOST_USER_ADD_MEM_REG doesn't have a documented return value, which is the desired behaviour in the non-postcopy case. It also implemented like this in QEMU and rust-vmm, though libvhost-user is buggy and sometimes sends an unexpected reply. This will be fixed in a separate patch. However, in postcopy mode it does reply like VHOST_USER_SET_MEM_TABLE. This behaviour is shared between libvhost-user and QEMU; rust-vmm doesn't implement postcopy mode yet. Mention it explicitly in the spec. * The specification doesn't mention how VHOST_USER_REM_MEM_REG identifies the memory region to be removed. Change it to describe the existing behaviour of libvhost-user (guest address, user address and size must match). Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20220407133657.155281-2-kwolf@redhat.com> Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> |
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| _templates | ||
| about | ||
| config | ||
| devel | ||
| interop | ||
| specs | ||
| sphinx | ||
| sphinx-static | ||
| spin | ||
| system | ||
| tools | ||
| user | ||
| block-replication.txt | ||
| bypass-iommu.txt | ||
| COLO-FT.txt | ||
| colo-proxy.txt | ||
| conf.py | ||
| defs.rst.inc | ||
| hyperv.txt | ||
| igd-assign.txt | ||
| image-fuzzer.txt | ||
| index.rst | ||
| memory-hotplug.txt | ||
| meson.build | ||
| multi-thread-compression.txt | ||
| multiseat.txt | ||
| nvdimm.txt | ||
| pci_expander_bridge.txt | ||
| pcie_pci_bridge.txt | ||
| pcie_sriov.txt | ||
| pcie.txt | ||
| pvrdma.txt | ||
| qcow2-cache.txt | ||
| qdev-device-use.txt | ||
| qemu-option-trace.rst.inc | ||
| qemupciserial.inf | ||
| rdma.txt | ||
| replay.txt | ||
| spice-port-fqdn.txt | ||
| throttle.txt | ||
| u2f.txt | ||
| xbzrle.txt | ||
| xen-save-devices-state.txt | ||