[PATCH v3 3/6] efi: mm: Always request a fixed number of pages on init

[Patrick Steinhardt <ps@pks.im>]

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When initializing the EFI memory subsytem, 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>
---
 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 9838fb2f5..4d276bc87 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;
@@ -478,23 +477,6 @@ 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,
@@ -583,8 +565,6 @@ 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;
 
   /* Prepare a memory region to store two memory maps.  */
@@ -624,22 +604,13 @@ 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.  */
-- 
2.32.0


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