debian/patches/0001-OvmfPkg-PlatformInitLib-limit-phys-bits-to-46.patch

   1 From 89a12f2a42b989e7925b4a71e503209971eaa271 Mon Sep 17 00:00:00 2001
   2 From: Gerd Hoffmann <kraxel@redhat.com>
   3 Date: Thu, 1 Jun 2023 09:57:31 +0200
   4 Subject: [PATCH] OvmfPkg/PlatformInitLib: limit phys-bits to 46.
   5
   6 Older linux kernels have problems with phys-bits larger than 46,
   7 ubuntu 18.04 (kernel 4.15) has been reported to be affected.
   8
   9 Reduce phys-bits limit from 47 to 46.
  10
  11 Reported-by: Fiona Ebner <f.ebner@proxmox.com>
  12 Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
  13 ---
  14  OvmfPkg/Library/PlatformInitLib/MemDetect.c | 9 ++++++---
  15  1 file changed, 6 insertions(+), 3 deletions(-)
  16
  17 diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
  18 index 38cece9173..4d0522ce22 100644
  19 --- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
  20 +++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
  21 @@ -657,16 +657,19 @@ PlatformAddressWidthFromCpuid (
  22      ));
  23
  24    if (Valid) {
  25 -    if (PhysBits > 47) {
  26 +    if (PhysBits > 46) {
  27        /*
  28         * Avoid 5-level paging altogether for now, which limits
  29         * PhysBits to 48.  Also avoid using address bit 48, due to sign
  30         * extension we can't identity-map these addresses (and lots of
  31         * places in edk2 assume we have everything identity-mapped).
  32         * So the actual limit is 47.
  33 +       *
  34 +       * Also some older linux kernels apparently have problems handling
  35 +       * phys-bits > 46 correctly, so use that as limit.
  36         */
  37 -      DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 47 (avoid 5-level paging)\n", __func__));
  38 -      PhysBits = 47;
  39 +      DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 46 (avoid 5-level paging)\n", __func__));
  40 +      PhysBits = 46;
  41      }
  42
  43      if (!Page1GSupport && (PhysBits > 40)) {
  44 --
  45 2.39.2
  46