From: Thomas Lamprecht <t.lamprecht@proxmox.com>
Date: Thu, 17 Nov 2022 16:40:35 +0000 (+0100)
Subject: memory hot plug: round down to nearest even phys-bits for heuristics
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=305e9cec5d74610650aa627176d048b1c7e44877;p=qemu-server.git

memory hot plug: round down to nearest even phys-bits for heuristics

Mira found out that 41 phys-bits the limit is pretty much the same as
with 40, as such odd sizes are a bit unexpected anyway lets mask the
LSB and use that as base, that way we're good again.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---

diff --git a/PVE/QemuServer/Memory.pm b/PVE/QemuServer/Memory.pm
index 013917e..f8fc534 100644
--- a/PVE/QemuServer/Memory.pm
+++ b/PVE/QemuServer/Memory.pm
@@ -55,8 +55,10 @@ my sub get_max_mem {
 	}
     }
 
-    # remove 20 bits to get MB and half that as QEMU needs some overhead
-    my $bits_to_max_mem = int(1 << ($bits - 21));
+    $bits = $bits & ~1; # round down to nearest even as limit is lower with odd bit sizes
+
+    # heuristic: remove 20 bits to get MB and half that as QEMU needs some overhead
+    my $bits_to_max_mem = int(1<<($bits - 21));
 
     return $bits_to_max_mem > 4*1024*1024 ? 4*1024*1024 : $bits_to_max_mem;
 }