grub2/0312-kern-efi-mm-Always-request-a-fixed-number-of-pages-o.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Patrick Steinhardt <ps@pks.im>
Date: Thu, 21 Apr 2022 15:24:19 +1000
Subject: [PATCH] kern/efi/mm: Always request a fixed number of pages on init

When initializing the EFI memory subsystem, we will by default request
a quarter of the available memory, bounded by a minimum/maximum value.
Given that we're about to extend the EFI memory system to dynamically
request additional pages from the firmware as required, this scaling of
requested memory based on available memory will not make a lot of sense
anymore.

Remove this logic as a preparatory patch such that we'll instead defer
to the runtime memory allocator. Note that ideally, we'd want to change
this after dynamic requesting of pages has been implemented for the EFI
platform. But because we'll need to split up initialization of the
memory subsystem and the request of pages from the firmware, we'd have
to duplicate quite some logic at first only to remove it afterwards
again. This seems quite pointless, so we instead have patches slightly
out of order.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Patrick Steinhardt <ps@pks.im>
(cherry picked from commit 938c3760b8c0fca759140be48307179b50107ff6)
---
 grub-core/kern/efi/mm.c | 35 +++--------------------------------
 1 file changed, 3 insertions(+), 32 deletions(-)

diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
index e460b072e6..782a1365a1 100644
--- a/grub-core/kern/efi/mm.c
+++ b/grub-core/kern/efi/mm.c
@@ -38,9 +38,8 @@
    a multiplier of 4KB.  */
 #define MEMORY_MAP_SIZE	0x3000
 
-/* The minimum and maximum heap size for GRUB itself.  */
-#define MIN_HEAP_SIZE	0x100000
-#define MAX_HEAP_SIZE	(1600 * 0x100000)
+/* The default heap size for GRUB itself in bytes.  */
+#define DEFAULT_HEAP_SIZE	0x100000
 
 static void *finish_mmap_buf = 0;
 static grub_efi_uintn_t finish_mmap_size = 0;
@@ -514,23 +513,6 @@ filter_memory_map (grub_efi_memory_descriptor_t *memory_map,
   return filtered_desc;
 }
 
-/* Return the total number of pages.  */
-static grub_efi_uint64_t
-get_total_pages (grub_efi_memory_descriptor_t *memory_map,
-		 grub_efi_uintn_t desc_size,
-		 grub_efi_memory_descriptor_t *memory_map_end)
-{
-  grub_efi_memory_descriptor_t *desc;
-  grub_efi_uint64_t total = 0;
-
-  for (desc = memory_map;
-       desc < memory_map_end;
-       desc = NEXT_MEMORY_DESCRIPTOR (desc, desc_size))
-    total += desc->num_pages;
-
-  return total;
-}
-
 /* Add memory regions.  */
 static void
 add_memory_regions (grub_efi_memory_descriptor_t *memory_map,
@@ -694,8 +676,6 @@ grub_efi_mm_init (void)
   grub_efi_memory_descriptor_t *filtered_memory_map_end;
   grub_efi_uintn_t map_size;
   grub_efi_uintn_t desc_size;
-  grub_efi_uint64_t total_pages;
-  grub_efi_uint64_t required_pages;
   int mm_status;
 
   grub_nx_init ();
@@ -737,22 +717,13 @@ grub_efi_mm_init (void)
   filtered_memory_map_end = filter_memory_map (memory_map, filtered_memory_map,
 					       desc_size, memory_map_end);
 
-  /* By default, request a quarter of the available memory.  */
-  total_pages = get_total_pages (filtered_memory_map, desc_size,
-				 filtered_memory_map_end);
-  required_pages = (total_pages >> 2);
-  if (required_pages < BYTES_TO_PAGES (MIN_HEAP_SIZE))
-    required_pages = BYTES_TO_PAGES (MIN_HEAP_SIZE);
-  else if (required_pages > BYTES_TO_PAGES (MAX_HEAP_SIZE))
-    required_pages = BYTES_TO_PAGES (MAX_HEAP_SIZE);
-
   /* Sort the filtered descriptors, so that GRUB can allocate pages
      from smaller regions.  */
   sort_memory_map (filtered_memory_map, desc_size, filtered_memory_map_end);
 
   /* Allocate memory regions for GRUB's memory management.  */
   add_memory_regions (filtered_memory_map, desc_size,
-		      filtered_memory_map_end, required_pages);
+		      filtered_memory_map_end, BYTES_TO_PAGES (DEFAULT_HEAP_SIZE));
 
 #if 0
   /* For debug.  */