virtio-balloon: use smaller config on older guests

[pve-qemu.git] / debian / patches / extra / 0003-virtio-balloon-use-smaller-config-on-older-guests.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Wolfgang Bumiller <w.bumiller@proxmox.com>
Date: Tue, 2 Jul 2019 09:23:43 +0200
Subject: [PATCH] virtio-balloon: use smaller config on older guests

The increased config size changes its alignment requirements
preventing guests from migrating from old qemu versions if
their balloon mapping isn't stricter aligned.
So base the default config size on the machine version.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
---
 hw/i386/pc.c                       |  2 ++
 hw/virtio/virtio-balloon.c         | 52 +++++++++++++++++++++++++++---
 include/hw/virtio/virtio-balloon.h |  1 +
 3 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index f2c15bf1f2..a6c01203f5 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -77,6 +77,7 @@
 #include "hw/i386/intel_iommu.h"
 #include "hw/net/ne2000-isa.h"
 #include "standard-headers/asm-x86/bootparam.h"
+#include "hw/virtio/virtio-balloon.h"
 
 /* debug PC/ISA interrupts */
 //#define DEBUG_IRQ
@@ -137,6 +138,7 @@ GlobalProperty pc_compat_3_1[] = {
     { "Icelake-Server" "-" TYPE_X86_CPU,      "mpx", "on" },
     { "Cascadelake-Server" "-" TYPE_X86_CPU, "stepping", "5" },
     { TYPE_X86_CPU, "x-intel-pt-auto-level", "off" },
+    { TYPE_VIRTIO_BALLOON, "x-use-large-balloon-config", "off" },
 };
 const size_t pc_compat_3_1_len = G_N_ELEMENTS(pc_compat_3_1);
 
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 2112874055..d10298786d 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -328,6 +328,28 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
     balloon_stats_change_timer(s, 0);
 }
 
+static void balloon_get_large_config(Object *obj, Visitor *v,
+                                     const char *name, void *opaque,
+                                     Error **errp)
+{
+    VirtIOBalloon *s = opaque;
+    visit_type_bool(v, name, &s->use_large_config, errp);
+}
+
+static void balloon_set_large_config(Object *obj, Visitor *v,
+                                     const char *name, void *opaque,
+                                     Error **errp)
+{
+    VirtIOBalloon *s = opaque;
+    DeviceState *dev = DEVICE(s);
+
+    if (dev->realized) {
+        error_setg(errp, "balloon config size cannot be changed at runtime");
+    } else {
+        visit_type_bool(v, name, &s->use_large_config, errp);
+    }
+}
+
 static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 {
     VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
@@ -526,6 +548,17 @@ static bool virtio_balloon_free_page_support(void *opaque)
     return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT);
 }
 
+static size_t virtio_balloon_config_size(void *opaque)
+{
+    VirtIOBalloon *s = opaque;
+
+    if (s->use_large_config) {
+        return sizeof(struct virtio_balloon_config);
+    } else {
+        return offsetof(struct virtio_balloon_config, free_page_report_cmd_id);
+    }
+}
+
 static void virtio_balloon_free_page_start(VirtIOBalloon *s)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
@@ -635,7 +668,7 @@ 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 +712,7 @@ 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 +799,7 @@ 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);
@@ -791,7 +824,7 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
         s->free_page_report_notify.notify =
                                        virtio_balloon_free_page_report_notify;
         precopy_add_notifier(&s->free_page_report_notify);
-        if (s->iothread) {
+        if (s->iothread && s->use_large_config) {
             object_ref(OBJECT(s->iothread));
             s->free_page_bh = aio_bh_new(iothread_get_aio_context(s->iothread),
                                        virtio_ballloon_get_free_page_hints, s);
@@ -804,6 +837,11 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
             virtio_error(vdev, "iothread is missing");
         }
     }
+
+    if (!s->use_large_config) {
+        s->host_features &= ~(1 << VIRTIO_BALLOON_F_PAGE_POISON);
+    }
+
     reset_stats(s);
 }
 
@@ -880,6 +918,12 @@ static void virtio_balloon_instance_init(Object *obj)
                         balloon_stats_get_poll_interval,
                         balloon_stats_set_poll_interval,
                         NULL, s, NULL);
+
+    s->use_large_config = true;
+    object_property_add(obj, "x-use-large-balloon-config", "bool",
+                        balloon_get_large_config,
+                        balloon_set_large_config,
+                        NULL, s, NULL);
 }
 
 static const VMStateDescription vmstate_virtio_balloon = {
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index 1afafb12f6..f212c08bd7 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -45,6 +45,7 @@ enum virtio_balloon_free_page_report_status {
 typedef struct VirtIOBalloon {
     VirtIODevice parent_obj;
     VirtQueue *ivq, *dvq, *svq, *free_page_vq;
+    bool use_large_config;
     uint32_t free_page_report_status;
     uint32_t num_pages;
     uint32_t actual;