Host Memory Backends and Memory devices queue 2023-07-12

[GIT PULL 12/21] virtio-mem: Skip most of virtio_mem_unplug_all() without plugged memory

David Hildenbrand posted 21 patches 2 years, 5 months ago

Download mbox

Maintainers: Peter Maydell <peter.maydell@linaro.org>, "Michael S. Tsirkin" <mst@redhat.com>, Igor Mammedov <imammedo@redhat.com>, Ani Sinha <anisinha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <richard.henderson@linaro.org>, Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Xiaojuan Yang <yangxiaojuan@loongson.cn>, Song Gao <gaosong@loongson.cn>, David Hildenbrand <david@redhat.com>, Xiao Guangrong <xiaoguangrong.eric@gmail.com>, Daniel Henrique Barboza <danielhb413@gmail.com>, "Cédric Le Goater" <clg@kaod.org>, David Gibson <david@gibson.dropbear.id.au>, Greg Kurz <groug@kaod.org>, Harsh Prateek Bora <harshpb@linux.ibm.com>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Yanan Wang <wangyanan55@huawei.com>, Juan Quintela <quintela@redhat.com>, Peter Xu <peterx@redhat.com>, Leonardo Bras <leobras@redhat.com>

Expand all Fold all

[GIT PULL 12/21] virtio-mem: Skip most of virtio_mem_unplug_all() without plugged memory

Posted by David Hildenbrand 2 years, 5 months ago

Already when starting QEMU we perform one system reset that ends up
triggering virtio_mem_unplug_all() with no actual memory plugged yet.
That, in turn will trigger ram_block_discard_range() and perform some
other actions that are not required in that case.

Let's optimize virtio_mem_unplug_all() for the case that no memory is
plugged. This will be beneficial for x-ignore-shared support as well.

Message-ID: <20230706075612.67404-3-david@redhat.com>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/virtio/virtio-mem.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index ec0ae32589..a922c21380 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -621,20 +621,20 @@ static int virtio_mem_unplug_all(VirtIOMEM *vmem)
 {
     RAMBlock *rb = vmem->memdev->mr.ram_block;
 
-    if (virtio_mem_is_busy()) {
-        return -EBUSY;
-    }
-
-    if (ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb))) {
-        return -EBUSY;
-    }
-    virtio_mem_notify_unplug_all(vmem);
-
-    bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
     if (vmem->size) {
+        if (virtio_mem_is_busy()) {
+            return -EBUSY;
+        }
+        if (ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb))) {
+            return -EBUSY;
+        }
+        virtio_mem_notify_unplug_all(vmem);
+
+        bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
         vmem->size = 0;
         notifier_list_notify(&vmem->size_change_notifiers, &vmem->size);
     }
+
     trace_virtio_mem_unplugged_all();
     virtio_mem_resize_usable_region(vmem, vmem->requested_size, true);
     return 0;
-- 
2.41.0