770f06a5a4
- Add DMABUF support [VOYAGER-19 VOYAGER-53] - Accelerated SMMU device for GH GPU passthrough [VOYAGER-5 VOYAGER-16 VOYAGER-17 VOYAGER-48] - Upgrade vEVENTQ(v8) and vCMDQ (v3) [VOYAGER-249] - Resolves: VOYAGER-5 (Backport CMDQV support) - Resolves: VOYAGER-16 (Backport HW accelerated nesting support for arm SMMUv3) - Resolves: VOYAGER-17 (Backport vEVENTQ support for smmuv3) - Resolves: VOYAGER-19 (Backport vfio: Add DMABUF support for PCI BAR regions - qemu-kvm) - Resolves: VOYAGER-48 (qemu-kvm coredump when using traditional smmuv3 device without any GPU device) - Resolves: VOYAGER-53 (qemu-kvm coredump when hotunplug NIC VF interface without smmuv3) - Resolves: VOYAGER-249 (tegra241_cmdqv raises error when booting guest with NIC and GPU and smmuv3 pcibus specified in desc and both cmdqv on)
120 lines
4.9 KiB
Diff
120 lines
4.9 KiB
Diff
From 6063efec412ac2edb509af082bbac1721beef88f Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Thu, 29 Jan 2026 16:20:35 -0500
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Subject: [PATCH] docs: add SCSI migrate-pr documentation
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 464: scsi: persistent reservation live migration
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RH-Jira: RHEL-132749
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Commit: [5/5] e081d8f5e12d1228cd3de395964c0cb4d483559e (stefanha/centos-stream-qemu-kvm)
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Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: 20260129212035.219676-6-stefanha@redhat.com
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit a67819adb2212977360e9290bd005badb07dd2e4)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Patch-name: kvm-docs-add-SCSI-migrate-pr-documentation.patch
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Patch-id: 126
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Patch-present-in-specfile: True
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---
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docs/system/device-emulation.rst | 1 +
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docs/system/devices/scsi/index.rst | 10 +++++
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docs/system/devices/scsi/migrate-pr.rst | 54 +++++++++++++++++++++++++
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3 files changed, 65 insertions(+)
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create mode 100644 docs/system/devices/scsi/index.rst
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create mode 100644 docs/system/devices/scsi/migrate-pr.rst
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diff --git a/docs/system/device-emulation.rst b/docs/system/device-emulation.rst
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index 911381643f..72a9dbd54d 100644
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--- a/docs/system/device-emulation.rst
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+++ b/docs/system/device-emulation.rst
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@@ -91,6 +91,7 @@ Emulated Devices
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devices/keyboard.rst
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devices/net.rst
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devices/nvme.rst
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+ devices/scsi/index.rst
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devices/usb.rst
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devices/vhost-user.rst
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devices/virtio-gpu.rst
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diff --git a/docs/system/devices/scsi/index.rst b/docs/system/devices/scsi/index.rst
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new file mode 100644
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index 0000000000..4f0929b0ca
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--- /dev/null
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+++ b/docs/system/devices/scsi/index.rst
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@@ -0,0 +1,10 @@
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+SCSI Devices
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+============
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+
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+Several SCSI devices are available in QEMU. They are primarily used for block
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+storage.
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+
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+.. toctree::
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+ :maxdepth: 1
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+
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+ migrate-pr.rst
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diff --git a/docs/system/devices/scsi/migrate-pr.rst b/docs/system/devices/scsi/migrate-pr.rst
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new file mode 100644
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index 0000000000..a8f2790a86
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--- /dev/null
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+++ b/docs/system/devices/scsi/migrate-pr.rst
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@@ -0,0 +1,54 @@
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+..
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+ SPDX-License-Identifier: GPL-2.0-or-later
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+
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+.. _scsi_migrate_pr:
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+
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+SCSI Persistent Reservation Live Migration
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+==========================================
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+
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+This document explains how to live migrate SCSI Persistent Reservations.
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+
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+The ``scsi-block`` device migrates SCSI Persistent Reservations when the
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+``migrate-pr=on`` parameter is given. Migration is enabled by default in
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+versioned machine types since QEMU 11.0. It is disabled by default on older
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+machine types and needs to be explicitly enabled with ``--device
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+scsi-block,migrate-pr=on,...``.
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+
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+When migration is enabled, QEMU snoops PERSISTENT RESERVATION OUT commands and
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+tracks the reservation key registered by the guest as well as reservations that
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+the guest acquires. This information is migrated along with the guest and the
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+destination QEMU submits a PERSISTENT RESERVATION OUT command with the PREEMPT
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+service action to atomically transfer the reservation to the destination before
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+the guest starts running on the destination.
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+
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+The following persistent reservation capabilities reported by the PERSISTENT
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+RESERVATION IN command with the REPORT CAPABILITIES service action are masked
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+from the guest by QEMU when migration is enabled:
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+
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+ * Specify Initiator Ports Capable (SIP_C)
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+ * All Target Ports Capable (ATC_C)
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+
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+When migration is disabled, the ``scsi-block`` device is live migrated but
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+reservations remain in place on the source. Usually this is not the intended
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+behavior unless there is another mechanism to update reservations during
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+migration. The PERSISTENT RESERVATION IN command also does not mask
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+capabilities reported to the guest when migration is disabled.
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+
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+Limitations
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+-----------
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+
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+QEMU does not remember snooped reservation details across restart, so software
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+inside the guest must acquire the reservation after boot in order for live
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+migration to work. Similarly, if the reservation is acquired outside the guest
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+then it will not live migrate along with the guest.
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+
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+Snooping only considers the PERSISTENT RESERVATION OUT commands from the guest
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+and does not track reservation changes made by other SCSI initiators. QEMU's
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+snooped reservation details can become stale if another SCSI initiator
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+makes changes to the reservation.
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+
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+Guests running on the same host share a single SCSI initiator identity unless
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+Fibre Channel N_Port ID Virtualization is configured. As a consequence,
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+multiple guests on the same hosts may observe unexpected behavior if they use
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+the same physical LUN. From the LUN's perspective all guests are the same
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+initiator and there is no way to distinguish between guests.
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