[Qemu-devel] [PATCH] hw/i386/pc: run the multiboot loader before the PVH loader

[Stefano Garzarella <sgarzare@redhat.com>]

Some multiboot images could be in the ELF format. In the current
implementation QEMU fails because we try to load these images
as a PVH image.

In order to fix this issue, we should try multiboot first (we
already check the multiboot magic header before to load it).
If it is not a multiboot image, we can try the PVH loader.

Fixes: ab969087da6 ("pvh: Boot uncompressed kernel using direct boot ABI", 2019-01-15)
Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 hw/i386/pc.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 3889eccdc3..207c267093 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1209,6 +1209,17 @@ static void load_linux(PCMachineState *pcms,
     if (ldl_p(header+0x202) == 0x53726448) {
         protocol = lduw_p(header+0x206);
     } else {
+        /*
+         * This could be a multiboot kernel. If it is, let's stop treating it
+         * like a Linux kernel.
+         * Note: some multiboot images could be in the ELF format (the same of
+         * PVH), so we try multiboot first since we check the multiboot magic
+         * header before to load it.
+         */
+        if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename,
+                           kernel_cmdline, kernel_size, header)) {
+            return;
+        }
         /*
          * Check if the file is an uncompressed kernel file (ELF) and load it,
          * saving the PVH entry point used by the x86/HVM direct boot ABI.
@@ -1262,12 +1273,6 @@ static void load_linux(PCMachineState *pcms,
 
             return;
         }
-        /* This looks like a multiboot kernel. If it is, let's stop
-           treating it like a Linux kernel. */
-        if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename,
-                           kernel_cmdline, kernel_size, header)) {
-            return;
-        }
         protocol = 0;
     }
 
-- 
2.20.1