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Tsirkin" , Marcel Apfelbaum , qemu-devel@nongnu.org (open list:All patches CC here) Subject: [PATCH v4] piix: fix xenfv regression, add compat machine xenfv-qemu4 Date: Fri, 27 Mar 2020 16:18:40 +0100 Message-Id: <20200327151841.13877-1-olaf@aepfle.de> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200113174521.3336-1-olaf@aepfle.de> References: <20200113174521.3336-1-olaf@aepfle.de> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a01:238:20a:202:5301::7 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Olaf Hering Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" With qemu4 an incompatible change was added to pc_piix, which makes it practical impossible to migrate domUs started with qemu2 or qemu3 to newer qemu versions. Commit 7fccf2a06890e3bc3b30e29827ad3fb93fe88fea added and enabled a new member "smbus_no_migration_support". In commit 4ab2f2a8aabfea95cc53c64e13b3f67960b27fdf the vmstate_acpi got new elements, which are conditionally filled. As a result, an incoming migration expected smbus related data unless smbus migration was disabled for a given MachineClass. Since first commit forgot to handle 'xenfv', domUs started with qemu4 are incompatible with their qemu3 siblings. Using other existing machine types, such as 'pc-i440fx-3.1', is not possible because 'xenfv' creates the 'xen-platform' PCI device at 00:02.0, while all other variants to run a domU would create it at 00:04.0. To cover both the existing and the broken case of 'xenfv' in a single qemu binary, a new compatibility variant of 'xenfv-qemu4' must be added which targets domUs started with qemu-4.0, qemu-4.1 and qemu-4.2. The existing 'xenfv' restores compatibility of qemu5+ with qemu2/3. Host admins who started domUs with qemu-4.x have to use a wrapper script which appends '-machine xenfv-qemu4' to the device-model command line. This is only required if there is no maintenance window which allows to temporary shutdown the domU and restart it with a fixed device-model. The wrapper script is as simple as this: #!/bin/sh exec /usr/bin/qemu-system-i386 "$@" -machine xenfv-qemu4 With xl this script will be enabled with device_model_override=, see xl.cfg(5). To live migrate a domU, adjust the existing domU.cfg and pass it to xl migrate or xl save/restore: xl migrate -C new-domU.cfg domU remote-host xl save domU CheckpointFile new-domU.cfg xl restore new-domU.cfg CheckpointFile With libvirt this script will be enabled with the element in domU.xml. Use 'virsh edit' prior 'virsh migrate' to replace the existing element to point it to the wrapper script. Signed-off-by: Olaf Hering --- hw/i386/pc_piix.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c index e6756216f9..c565f41791 100644 --- a/hw/i386/pc_piix.c +++ b/hw/i386/pc_piix.c @@ -948,8 +948,21 @@ DEFINE_PC_MACHINE(isapc, "isapc", pc_init_isa, #ifdef CONFIG_XEN +static void xenfv_qemu_4_x_machine_options(MachineClass *m) +{ + pc_i440fx_4_2_machine_options(m); + m->desc = "Xen Fully-virtualized PC (qemu 4.x compat)"; + m->max_cpus = HVM_MAX_VCPUS; + m->default_machine_opts = "accel=xen"; + m->smbus_no_migration_support = false; +} + +DEFINE_PC_MACHINE(xenfv_qemu4, "xenfv-qemu4", pc_xen_hvm_init, + xenfv_qemu_4_x_machine_options); + static void xenfv_machine_options(MachineClass *m) { + pc_i440fx_3_1_machine_options(m); m->desc = "Xen Fully-virtualized PC"; m->max_cpus = HVM_MAX_VCPUS; m->default_machine_opts = "accel=xen";