[qemu-xen staging-4.18] qxl: don't assert() if device isn't yet initialized

[patchbot@xxxxxxx]

commit 5929f5309194e46f40b20aa07797f531663e323f
Author:     Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>
AuthorDate: Mon Aug 14 23:33:30 2023 +0400
Commit:     Michael Tokarev <mjt@xxxxxxxxxx>
CommitDate: Sun Sep 10 19:40:11 2023 +0300

    qxl: don't assert() if device isn't yet initialized
    
    If the PCI BAR isn't yet mapped or was unmapped, QXL_IO_SET_MODE will
    assert(). Instead, report a guest bug and keep going.
    
    This can be reproduced with:
    
    cat << EOF | ./qemu-system-x86_64 -vga qxl -m 2048 -nodefaults -qtest stdio
    outl 0xcf8 0x8000101c
    outl 0xcfc 0xc000
    outl 0xcf8 0x80001001
    outl 0xcfc 0x01000000
    outl 0xc006 0x00
    EOF
    
    Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1829
    
    Signed-off-by: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>
    Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
    Cc: qemu-stable@xxxxxxxxxx
    Signed-off-by: Michael Tokarev <mjt@xxxxxxxxxx>
    (cherry picked from commit 95bef686e490bc3afc3f51f5fc6e20bf260b938c)
    Signed-off-by: Michael Tokarev <mjt@xxxxxxxxxx>
---
 hw/display/qxl.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/display/qxl.c b/hw/display/qxl.c
index f1c0eb7dfc..70b73820b2 100644
--- a/hw/display/qxl.c
+++ b/hw/display/qxl.c
@@ -1591,7 +1591,10 @@ static void qxl_set_mode(PCIQXLDevice *d, unsigned int 
modenr, int loadvm)
     }
 
     d->guest_slots[0].slot = slot;
-    assert(qxl_add_memslot(d, 0, devmem, QXL_SYNC) == 0);
+    if (qxl_add_memslot(d, 0, devmem, QXL_SYNC) != 0) {
+        qxl_set_guest_bug(d, "device isn't initialized yet");
+        return;
+    }
 
     d->guest_primary.surface = surface;
     qxl_create_guest_primary(d, 0, QXL_SYNC);
--
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