128 lines
5.2 KiB
Diff
128 lines
5.2 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Wed, 10 Jul 2019 16:14:40 +0200
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Subject: [PATCH] virtio-balloon: fix QEMU 4.0 config size migration
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incompatibility
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The virtio-balloon config size changed in QEMU 4.0 even for existing
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machine types. Migration from QEMU 3.1 to 4.0 can fail in some
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circumstances with the following error:
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qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x10 read: a1 device: 1 cmask: ff wmask: c0 w1cmask:0
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This happens because the virtio-balloon config size affects the VIRTIO
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Legacy I/O Memory PCI BAR size.
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Introduce a qdev property called "qemu-4-0-config-size" and enable it
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only for the QEMU 4.0 machine types. This way <4.0 machine types use
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the old size, 4.0 uses the larger size, and >4.0 machine types use the
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appropriate size depending on enabled virtio-balloon features.
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Live migration to and from old QEMUs to QEMU 4.1 works again as long as
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a versioned machine type is specified (do not use just "pc"!).
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Originally-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
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---
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hw/core/machine.c | 1 +
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hw/virtio/virtio-balloon.c | 28 +++++++++++++++++++++++++---
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include/hw/virtio/virtio-balloon.h | 2 ++
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3 files changed, 28 insertions(+), 3 deletions(-)
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diff --git a/hw/core/machine.c b/hw/core/machine.c
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index 743fef2898..f25c91875f 100644
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--- a/hw/core/machine.c
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+++ b/hw/core/machine.c
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@@ -36,6 +36,7 @@ GlobalProperty hw_compat_3_1[] = {
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{ "usb-kbd", "serial", "42" },
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{ "virtio-blk-device", "discard", "false" },
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{ "virtio-blk-device", "write-zeroes", "false" },
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+ { "virtio-balloon-device", "qemu-4-0-config-size", "false" },
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};
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const size_t hw_compat_3_1_len = G_N_ELEMENTS(hw_compat_3_1);
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diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
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index d96e4aa96f..c8788ea18d 100644
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--- a/hw/virtio/virtio-balloon.c
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+++ b/hw/virtio/virtio-balloon.c
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@@ -615,6 +615,22 @@ virtio_balloon_free_page_report_notify(NotifierWithReturn *n, void *data)
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return 0;
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}
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+static size_t virtio_balloon_config_size(VirtIOBalloon *s)
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+{
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+ uint64_t features = s->host_features;
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+
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+ if (s->qemu_4_0_config_size) {
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+ return sizeof(struct virtio_balloon_config);
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+ }
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+ if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON)) {
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+ return sizeof(struct virtio_balloon_config);
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+ }
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+ if (virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
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+ return offsetof(struct virtio_balloon_config, poison_val);
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+ }
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+ return offsetof(struct virtio_balloon_config, free_page_report_cmd_id);
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+}
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+
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static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
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{
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VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
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@@ -635,7 +651,7 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
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}
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trace_virtio_balloon_get_config(config.num_pages, config.actual);
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- memcpy(config_data, &config, sizeof(struct virtio_balloon_config));
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+ memcpy(config_data, &config, virtio_balloon_config_size(dev));
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}
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static int build_dimm_list(Object *obj, void *opaque)
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@@ -679,7 +695,7 @@ static void virtio_balloon_set_config(VirtIODevice *vdev,
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uint32_t oldactual = dev->actual;
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ram_addr_t vm_ram_size = get_current_ram_size();
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- memcpy(&config, config_data, sizeof(struct virtio_balloon_config));
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+ memcpy(&config, config_data, virtio_balloon_config_size(dev));
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dev->actual = le32_to_cpu(config.actual);
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if (dev->actual != oldactual) {
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qapi_event_send_balloon_change(vm_ram_size -
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@@ -795,7 +811,7 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
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int ret;
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virtio_init(vdev, "virtio-balloon", VIRTIO_ID_BALLOON,
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- sizeof(struct virtio_balloon_config));
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+ virtio_balloon_config_size(s));
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ret = qemu_add_balloon_handler(virtio_balloon_to_target,
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virtio_balloon_stat, s);
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@@ -926,6 +942,12 @@ static Property virtio_balloon_properties[] = {
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VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
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DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features,
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VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
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+ /* QEMU 4.0 accidentally changed the config size even when free-page-hint
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+ * is disabled, resulting in QEMU 3.1 migration incompatibility. This
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+ * property retains this quirk for QEMU 4.1 machine types.
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+ */
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+ DEFINE_PROP_BOOL("qemu-4-0-config-size", VirtIOBalloon,
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+ qemu_4_0_config_size, false),
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DEFINE_PROP_LINK("iothread", VirtIOBalloon, iothread, TYPE_IOTHREAD,
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IOThread *),
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DEFINE_PROP_END_OF_LIST(),
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diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
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index 1afafb12f6..5a99293a45 100644
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--- a/include/hw/virtio/virtio-balloon.h
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+++ b/include/hw/virtio/virtio-balloon.h
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@@ -71,6 +71,8 @@ typedef struct VirtIOBalloon {
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int64_t stats_poll_interval;
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uint32_t host_features;
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PartiallyBalloonedPage *pbp;
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+
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+ bool qemu_4_0_config_size;
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} VirtIOBalloon;
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#endif
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--
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2.20.1
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