Merge tag 'pull-hv-balloon-20231106' of https://github.com/maciejsszmigiero/qemu into staging

Hyper-V Dynamic Memory protocol driver.

This driver is like virtio-balloon on steroids for Windows guests:
it allows both changing the guest memory allocation via ballooning and
inserting pieces of extra RAM into it on demand from a provided memory
backend via Windows-native Hyper-V Dynamic Memory protocol.

* Preparatory patches to support empty memory devices and ones with
large alignment requirements.

* Revert of recently added "hw/virtio/virtio-pmem: Replace impossible
check by assertion" commit 5960f254dbb4 since this series makes this
situation possible again.

* Protocol definitions.

* Hyper-V DM protocol driver (hv-balloon) base (ballooning only).

* Hyper-V DM protocol driver (hv-balloon) hot-add support.

* qapi query-memory-devices support for the driver.

* qapi HV_BALLOON_STATUS_REPORT event.

* The relevant PC machine plumbing.

* New MAINTAINERS entry for the above.

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# gpg: Signature made Mon 06 Nov 2023 22:08:18 HKT
# gpg:                using RSA key E2776AABA08E26FF5A1B4A0952B1D6E951D0CE07
# gpg: Good signature from "Maciej S. Szmigiero <mail@maciej.szmigiero.name>" [unknown]
# gpg: WARNING: This key is not certified with a trusted signature!
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* tag 'pull-hv-balloon-20231106' of https://github.com/maciejsszmigiero/qemu:
  MAINTAINERS: Add an entry for Hyper-V Dynamic Memory Protocol
  hw/i386/pc: Support hv-balloon
  qapi: Add HV_BALLOON_STATUS_REPORT event and its QMP query command
  qapi: Add query-memory-devices support to hv-balloon
  Add Hyper-V Dynamic Memory Protocol driver (hv-balloon) hot-add support
  Add Hyper-V Dynamic Memory Protocol driver (hv-balloon) base
  Add Hyper-V Dynamic Memory Protocol definitions
  memory-device: Drop size alignment check
  Revert "hw/virtio/virtio-pmem: Replace impossible check by assertion"
  memory-device: Support empty memory devices

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 40 insertions, 9 deletions

diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
index ae38f48f16..e0704b8dc3 100644
--- a/hw/mem/memory-device.c
+++ b/hw/mem/memory-device.c
@@ -20,6 +20,22 @@
 #include "exec/address-spaces.h"
 #include "trace.h"
 
+static bool memory_device_is_empty(const MemoryDeviceState *md)
+{
+    const MemoryDeviceClass *mdc = MEMORY_DEVICE_GET_CLASS(md);
+    Error *local_err = NULL;
+    MemoryRegion *mr;
+
+    /* dropping const here is fine as we don't touch the memory region */
+    mr = mdc->get_memory_region((MemoryDeviceState *)md, &local_err);
+    if (local_err) {
+        /* Not empty, we'll report errors later when ontaining the MR again. */
+        error_free(local_err);
+        return false;
+    }
+    return !mr;
+}
+
 static gint memory_device_addr_sort(gconstpointer a, gconstpointer b)
 {
     const MemoryDeviceState *md_a = MEMORY_DEVICE(a);
@@ -220,12 +236,6 @@ static uint64_t memory_device_get_free_addr(MachineState *ms,
         return 0;
     }
 
-    if (!QEMU_IS_ALIGNED(size, align)) {
-        error_setg(errp, "backend memory size must be multiple of 0x%"
-                   PRIx64, align);
-        return 0;
-    }
-
     if (hint) {
         if (range_init(&new, *hint, size) || !range_contains_range(&as, &new)) {
             error_setg(errp, "can't add memory device [0x%" PRIx64 ":0x%" PRIx64
@@ -249,6 +259,10 @@ static uint64_t memory_device_get_free_addr(MachineState *ms,
         uint64_t next_addr;
         Range tmp;
 
+        if (memory_device_is_empty(md)) {
+            continue;
+        }
+
         range_init_nofail(&tmp, mdc->get_addr(md),
                           memory_device_get_region_size(md, &error_abort));
 
@@ -292,6 +306,7 @@ MemoryDeviceInfoList *qmp_memory_device_list(void)
         const MemoryDeviceClass *mdc = MEMORY_DEVICE_GET_CLASS(item->data);
         MemoryDeviceInfo *info = g_new0(MemoryDeviceInfo, 1);
 
+        /* Let's query infotmation even for empty memory devices. */
         mdc->fill_device_info(md, info);
 
         QAPI_LIST_APPEND(tail, info);
@@ -311,7 +326,7 @@ static int memory_device_plugged_size(Object *obj, void *opaque)
         const MemoryDeviceState *md = MEMORY_DEVICE(obj);
         const MemoryDeviceClass *mdc = MEMORY_DEVICE_GET_CLASS(obj);
 
-        if (dev->realized) {
+        if (dev->realized && !memory_device_is_empty(md)) {
             *size += mdc->get_plugged_size(md, &error_abort);
         }
     }
@@ -337,6 +352,11 @@ void memory_device_pre_plug(MemoryDeviceState *md, MachineState *ms,
     uint64_t addr, align = 0;
     MemoryRegion *mr;
 
+    /* We support empty memory devices even without device memory. */
+    if (memory_device_is_empty(md)) {
+        return;
+    }
+
     if (!ms->device_memory) {
         error_setg(errp, "the configuration is not prepared for memory devices"
                          " (e.g., for memory hotplug), consider specifying the"
@@ -380,10 +400,17 @@ out:
 void memory_device_plug(MemoryDeviceState *md, MachineState *ms)
 {
     const MemoryDeviceClass *mdc = MEMORY_DEVICE_GET_CLASS(md);
-    const unsigned int memslots = memory_device_get_memslots(md);
-    const uint64_t addr = mdc->get_addr(md);
+    unsigned int memslots;
+    uint64_t addr;
     MemoryRegion *mr;
 
+    if (memory_device_is_empty(md)) {
+        return;
+    }
+
+    memslots = memory_device_get_memslots(md);
+    addr = mdc->get_addr(md);
+
     /*
      * We expect that a previous call to memory_device_pre_plug() succeeded, so
      * it can't fail at this point.
@@ -408,6 +435,10 @@ void memory_device_unplug(MemoryDeviceState *md, MachineState *ms)
     const unsigned int memslots = memory_device_get_memslots(md);
     MemoryRegion *mr;
 
+    if (memory_device_is_empty(md)) {
+        return;
+    }
+
     /*
      * We expect that a previous call to memory_device_pre_plug() succeeded, so
      * it can't fail at this point.