--- /dev/null
+From 89a12f2a42b989e7925b4a71e503209971eaa271 Mon Sep 17 00:00:00 2001
+From: Gerd Hoffmann <kraxel@redhat.com>
+Date: Thu, 1 Jun 2023 09:57:31 +0200
+Subject: [PATCH] OvmfPkg/PlatformInitLib: limit phys-bits to 46.
+
+Older linux kernels have problems with phys-bits larger than 46,
+ubuntu 18.04 (kernel 4.15) has been reported to be affected.
+
+Reduce phys-bits limit from 47 to 46.
+
+Reported-by: Fiona Ebner <f.ebner@proxmox.com>
+Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
+---
+ OvmfPkg/Library/PlatformInitLib/MemDetect.c | 9 ++++++---
+ 1 file changed, 6 insertions(+), 3 deletions(-)
+
+diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
+index 38cece9173..4d0522ce22 100644
+--- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
++++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
+@@ -657,16 +657,19 @@ PlatformAddressWidthFromCpuid (
+ ));
+
+ if (Valid) {
+- if (PhysBits > 47) {
++ if (PhysBits > 46) {
+ /*
+ * Avoid 5-level paging altogether for now, which limits
+ * PhysBits to 48. Also avoid using address bit 48, due to sign
+ * extension we can't identity-map these addresses (and lots of
+ * places in edk2 assume we have everything identity-mapped).
+ * So the actual limit is 47.
++ *
++ * Also some older linux kernels apparently have problems handling
++ * phys-bits > 46 correctly, so use that as limit.
+ */
+- DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 47 (avoid 5-level paging)\n", __func__));
+- PhysBits = 47;
++ DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 46 (avoid 5-level paging)\n", __func__));
++ PhysBits = 46;
+ }
+
+ if (!Page1GSupport && (PhysBits > 40)) {
+--
+2.39.2
+