From 2bbadb08ce272d65e1f78621002008b07d1e0f03 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 10 Jul 2019 16:14:40 +0200 Subject: virtio-balloon: fix QEMU 4.0 config size migration incompatibility The virtio-balloon config size changed in QEMU 4.0 even for existing machine types. Migration from QEMU 3.1 to 4.0 can fail in some circumstances with the following error: qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x10 read: a1 device: 1 cmask: ff wmask: c0 w1cmask:0 This happens because the virtio-balloon config size affects the VIRTIO Legacy I/O Memory PCI BAR size. Introduce a qdev property called "qemu-4-0-config-size" and enable it only for the QEMU 4.0 machine types. This way <4.0 machine types use the old size, 4.0 uses the larger size, and >4.0 machine types use the appropriate size depending on enabled virtio-balloon features. Live migration to and from old QEMUs to QEMU 4.1 works again as long as a versioned machine type is specified (do not use just "pc"!). Originally-by: Wolfgang Bumiller Signed-off-by: Stefan Hajnoczi Message-Id: <20190710141440.27635-1-stefanha@redhat.com> Reviewed-by: Dr. David Alan Gilbert Tested-by: Dr. David Alan Gilbert Tested-by: Wolfgang Bumiller Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/core/machine.c | 2 ++ hw/virtio/virtio-balloon.c | 28 +++++++++++++++++++++++++--- include/hw/virtio/virtio-balloon.h | 2 ++ 3 files changed, 29 insertions(+), 3 deletions(-) diff --git a/hw/core/machine.c b/hw/core/machine.c index 2be19ec..c4ead16 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -34,6 +34,7 @@ GlobalProperty hw_compat_4_0[] = { { "virtio-vga", "edid", "false" }, { "virtio-gpu-pci", "edid", "false" }, { "virtio-device", "use-started", "false" }, + { "virtio-balloon-device", "qemu-4-0-config-size", "true" }, }; const size_t hw_compat_4_0_len = G_N_ELEMENTS(hw_compat_4_0); @@ -49,6 +50,7 @@ GlobalProperty hw_compat_3_1[] = { { "usb-tablet", "serial", "42" }, { "virtio-blk-device", "discard", "false" }, { "virtio-blk-device", "write-zeroes", "false" }, + { "virtio-balloon-device", "qemu-4-0-config-size", "false" }, }; const size_t hw_compat_3_1_len = G_N_ELEMENTS(hw_compat_3_1); diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index 11fad86..e85d1c0 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -615,6 +615,22 @@ virtio_balloon_free_page_report_notify(NotifierWithReturn *n, void *data) return 0; } +static size_t virtio_balloon_config_size(VirtIOBalloon *s) +{ + uint64_t features = s->host_features; + + if (s->qemu_4_0_config_size) { + return sizeof(struct virtio_balloon_config); + } + if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON)) { + return sizeof(struct virtio_balloon_config); + } + if (virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { + return offsetof(struct virtio_balloon_config, poison_val); + } + return offsetof(struct virtio_balloon_config, free_page_report_cmd_id); +} + static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data) { VirtIOBalloon *dev = VIRTIO_BALLOON(vdev); @@ -635,7 +651,7 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data) } trace_virtio_balloon_get_config(config.num_pages, config.actual); - memcpy(config_data, &config, sizeof(struct virtio_balloon_config)); + memcpy(config_data, &config, virtio_balloon_config_size(dev)); } static int build_dimm_list(Object *obj, void *opaque) @@ -679,7 +695,7 @@ static void virtio_balloon_set_config(VirtIODevice *vdev, uint32_t oldactual = dev->actual; ram_addr_t vm_ram_size = get_current_ram_size(); - memcpy(&config, config_data, sizeof(struct virtio_balloon_config)); + memcpy(&config, config_data, virtio_balloon_config_size(dev)); dev->actual = le32_to_cpu(config.actual); if (dev->actual != oldactual) { qapi_event_send_balloon_change(vm_ram_size - @@ -766,7 +782,7 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp) int ret; virtio_init(vdev, "virtio-balloon", VIRTIO_ID_BALLOON, - sizeof(struct virtio_balloon_config)); + virtio_balloon_config_size(s)); ret = qemu_add_balloon_handler(virtio_balloon_to_target, virtio_balloon_stat, s); @@ -897,6 +913,12 @@ static Property virtio_balloon_properties[] = { VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false), DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features, VIRTIO_BALLOON_F_FREE_PAGE_HINT, false), + /* QEMU 4.0 accidentally changed the config size even when free-page-hint + * is disabled, resulting in QEMU 3.1 migration incompatibility. This + * property retains this quirk for QEMU 4.1 machine types. + */ + DEFINE_PROP_BOOL("qemu-4-0-config-size", VirtIOBalloon, + qemu_4_0_config_size, false), DEFINE_PROP_LINK("iothread", VirtIOBalloon, iothread, TYPE_IOTHREAD, IOThread *), DEFINE_PROP_END_OF_LIST(), diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h index 1afafb1..5a99293 100644 --- a/include/hw/virtio/virtio-balloon.h +++ b/include/hw/virtio/virtio-balloon.h @@ -71,6 +71,8 @@ typedef struct VirtIOBalloon { int64_t stats_poll_interval; uint32_t host_features; PartiallyBalloonedPage *pbp; + + bool qemu_4_0_config_size; } VirtIOBalloon; #endif -- cgit v1.1