[PATCH v5] limit physical address space size

[Gerd Hoffmann <kraxel@redhat.com>]

For better compatibility with old linux kernels,
see source code comment.

Related (same problem in ovmf):
https://github.com/tianocore/edk2/commit/c1e853769046

Cc: Claudio Fontana <cfontana@suse.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 src/fw/paravirt.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
index e5d4eca0cb5a..a2c9c64d5e78 100644
--- a/src/fw/paravirt.c
+++ b/src/fw/paravirt.c
@@ -182,6 +182,14 @@ static void physbits(int qemu_quirk)
             __func__, signature, pae ? "yes" : "no", CPULongMode ? "yes" : "no",
             physbits, valid ? "yes" : "no");
 
+    if (valid && physbits > 46) {
+        // Old linux kernels have trouble dealing with more than 46
+        // phys-bits, so avoid that for now.  Seems to be a bug in the
+        // virtio-pci driver.  Reported: centos-7, ubuntu-18.04
+        dprintf(1, "%s: using phys-bits=46 (old linux kernel compatibility)\n", __func__);
+        physbits = 46;
+    }
+
     if (valid)
         CPUPhysBits = physbits;
 }
-- 
2.41.0