[Qemu-devel] [PATCH] s390x: initialize virtio dev region

[Alexander Graf <agraf@suse.de>]

When running the s390x virtio machine we can potentially use uninitialized
memory for the virtio device backing ram. That can lead to weird breakge.

So let's better initialize it to 0 properly.

Reported-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
 hw/s390-virtio.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/hw/s390-virtio.c b/hw/s390-virtio.c
index 37945d5..d936809 100644
--- a/hw/s390-virtio.c
+++ b/hw/s390-virtio.c
@@ -165,6 +165,8 @@ static void s390_init(ram_addr_t my_ram_size,
     ram_addr_t initrd_size = 0;
     int shift = 0;
     uint8_t *storage_keys;
+    void *virtio_region;
+    target_phys_addr_t virtio_region_len;
     int i;
 
     /* s390x ram size detection needs a 16bit multiplier + an increment. So
@@ -184,6 +186,13 @@ static void s390_init(ram_addr_t my_ram_size,
     memory_region_init_ram(ram, NULL, "s390.ram", my_ram_size);
     memory_region_add_subregion(sysmem, 0, ram);
 
+    /* clear virtio region */
+    virtio_region_len = my_ram_size - ram_size;
+    virtio_region = cpu_physical_memory_map(ram_size, &virtio_region_len, true);
+    memset(virtio_region, 0, virtio_region_len);
+    cpu_physical_memory_unmap(virtio_region, virtio_region_len, 1,
+                              virtio_region_len);
+
     /* allocate storage keys */
     storage_keys = g_malloc0(my_ram_size / TARGET_PAGE_SIZE);
 
-- 
1.6.0.2