grub2/0001-powerpc-increase-MIN-RMA-size-for-CAS-negotiation.patch

From 68a2663cc316d55c2670a639c8a4a2a43ffdb141 Mon Sep 17 00:00:00 2001
From: Avnish Chouhan <avnish@linux.ibm.com>
Date: Wed, 15 Jan 2025 17:46:05 +0530
Subject: [PATCH] powerpc: increase MIN RMA size for CAS negotiation

Change RMA size from 512 MB to 768 MB which will result
in more memory at boot time for PowerPC. When PowerPC LPAR use/uses vTPM,
Secure Boot or FADump, the 512 MB RMA memory is not sufficient for
booting. With this 512 MB RMA, GRUB2 run out of memory and unable to
load the necessary. Sometimes even usage of CDROM which requires more
memory for installation along with the options mentioned above troubles
the boot memory and result in boot failures. Increasing the RMA size
will resolves multiple out of memory issues observed in PowerPC.

Failure details (GRUB2 debugs):

kern/ieee1275/init.c:550: mm requested region of size 8513000, flags 1
kern/ieee1275/init.c:563: Cannot satisfy allocation and retain minimum runtime
space
kern/ieee1275/init.c:550: mm requested region of size 8513000, flags 0
kern/ieee1275/init.c:563: Cannot satisfy allocation and retain minimum runtime
space
kern/file.c:215: Closing `/ppc/ppc64/initrd.img' ...
kern/disk.c:297: Closing
`ieee1275//vdevice/v-scsi
@30000067/disk@8300000000000000'...
kern/disk.c:311: Closing
`ieee1275//vdevice/v-scsi
@30000067/disk@8300000000000000' succeeded.
kern/file.c:225: Closing `/ppc/ppc64/initrd.img' failed with 3.
kern/file.c:148: Opening `/ppc/ppc64/initrd.img' succeeded.
error: ../../grub-core/kern/mm.c:552:out of memory.

Signed-off-by: Avnish Chouhan <avnish@linux.ibm.com>
Link: https://lore.kernel.org/r/20250115121605.56049-1-avnish@linux.ibm.com
---
 grub-core/kern/ieee1275/init.c | 33 +++++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/grub-core/kern/ieee1275/init.c b/grub-core/kern/ieee1275/init.c
index 8e08e5dd5c..e0634603ef 100644
--- a/grub-core/kern/ieee1275/init.c
+++ b/grub-core/kern/ieee1275/init.c
@@ -855,7 +855,7 @@ grub_ieee1275_ibm_cas (void)
     .vec1 = 0x80, /* ignore */
     .vec2_size = 1 + sizeof (struct option_vector2) - 2,
     .vec2 = {
-      0, 0, -1, -1, -1, -1, -1, 512, -1, 0, 48
+      0, 0, -1, -1, -1, -1, -1, 768, -1, 0, 48
     },
     .vec3_size = 2 - 1,
     .vec3 = 0x00e0, /* ask for FP + VMX + DFP but don't halt if unsatisfied */
@@ -892,6 +892,10 @@ grub_claim_heap (void)
 {
   grub_err_t err;
   grub_uint32_t total = HEAP_MAX_SIZE;
+#if defined(__powerpc__)
+  grub_uint32_t ibm_ca_support_reboot;
+  grub_ssize_t actual;
+#endif
 
   err = grub_ieee1275_total_mem (&rmo_top);
 
@@ -904,11 +908,32 @@ grub_claim_heap (void)
     grub_mm_add_region_fn = grub_ieee1275_mm_add_region;
 
 #if defined(__powerpc__)
+  /* Check if it's a CAS reboot with below property. If so, we will skip CAS call */
+  ibm_ca_support_reboot = 0;
+  if (grub_ieee1275_get_integer_property (grub_ieee1275_chosen,
+                                          "ibm,client-architecture-support-reboot",
+                                          &ibm_ca_support_reboot,
+                                          sizeof (ibm_ca_support_reboot),
+                                          &actual) >= 0)
+    grub_dprintf ("ieee1275", "ibm,client-architecture-support-reboot: %u\n",
+                  ibm_ca_support_reboot);
+
   if (grub_ieee1275_test_flag (GRUB_IEEE1275_FLAG_CAN_TRY_CAS_FOR_MORE_MEMORY))
     {
-      /* if we have an error, don't call CAS, just hope for the best */
-      if (err == GRUB_ERR_NONE && rmo_top < (512 * 1024 * 1024))
-	grub_ieee1275_ibm_cas ();
+      /*
+       * If we have an error or the reboot is detected as CAS reboot,
+       * don't call CAS, just hope for the best.
+       * Along with the above, if the rmo_top is 512 MB or above. We
+       * will skip the CAS call. Though if we call CAS, the rmo_top will
+       * be set to 768 MB via CAS Vector2. This condition is required to avoid the
+       * issue where the older Linux kernels are still using rmo_top as 512 MB.
+       * Calling CAS when rmo_top is less then 768 MB will result in a issue
+       * where we won't be able to boot to a newer kernel and continue to
+       * boot with older kernel having rmo_top as 512 MB.
+       */
+      if (!ibm_ca_support_reboot && err == GRUB_ERR_NONE
+          && rmo_top < (512 * 1024 * 1024))
+        grub_ieee1275_ibm_cas ();
     }
 #endif
 
-- 
2.48.1