From: David Woodhouse <dwmw@amazon.co.uk>
Date: Fri, 20 Oct 2023 17:00:18 +0000 (+0100)
Subject: hw/xen: use correct default protocol for xen-block on x86
X-Git-Tag: v8.2.0-rc0~32^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a1c1082908dde4867b1ac55f546bea0c17d52318;p=thirdparty%2Fqemu.git

hw/xen: use correct default protocol for xen-block on x86

Even on x86_64 the default protocol is the x86-32 one if the guest doesn't
specifically ask for x86-64.

Cc: qemu-stable@nongnu.org
Fixes: b6af8926fb85 ("xen: add implementations of xen-block connect and disconnect functions...")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---

diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index a07cd7eb5df..bfa53960c3a 100644
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -115,9 +115,13 @@ static void xen_block_connect(XenDevice *xendev, Error **errp)
         return;
     }
 
-    if (xen_device_frontend_scanf(xendev, "protocol", "%ms",
-                                  &str) != 1) {
-        protocol = BLKIF_PROTOCOL_NATIVE;
+    if (xen_device_frontend_scanf(xendev, "protocol", "%ms", &str) != 1) {
+        /* x86 defaults to the 32-bit protocol even for 64-bit guests. */
+        if (object_dynamic_cast(OBJECT(qdev_get_machine()), "x86-machine")) {
+            protocol = BLKIF_PROTOCOL_X86_32;
+        } else {
+            protocol = BLKIF_PROTOCOL_NATIVE;
+        }
     } else {
         if (strcmp(str, XEN_IO_PROTO_ABI_X86_32) == 0) {
             protocol = BLKIF_PROTOCOL_X86_32;