Commit 157266ed authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/boot/e820: Simplify append_e820_table() and remove restriction on single-entry tables 



So append_e820_table() begins with this weird condition that checks 'nr_entries':

    static int __init append_e820_table(struct boot_e820_entry *entries, u32 nr_entries)
    {
            /* Only one memory region (or negative)? Ignore it */
            if (nr_entries < 2)
                    return -1;

Firstly, 'nr_entries' has been an u32 since 2017 and cannot be negative.

Secondly, there's nothing inherently wrong with single-entry E820 maps,
especially in virtualized environments.

So remove this restriction and remove the __append_e820_table()
indirection.

Also:

 - fix/update comments
 - remove obsolete comments

This shrinks the generated code a bit as well:

   text       data        bss        dec        hex    filename
   7549      44072          0      51621       c9a5    e820.o.before
   7533      44072          0      51605       c995    e820.o.after

Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20250515120549.2820541-26-mingo@kernel.org
parent af0cf164

arch/x86/kernel/e820.c

+11 −24
Original line number Diff line number Diff line
@@ -441,7 +441,12 @@ __init int e820__update_table(struct e820_table *table) 
	return 0;

}



__init static int __append_e820_table(struct boot_e820_entry *entries, u32 nr_entries)

/*

 * Copy the BIOS E820 map into the kernel's e820_table.

 *

 * Sanity-check it while we're at it..

 */

__init static int append_e820_table(struct boot_e820_entry *entries, u32 nr_entries)

{

	struct boot_e820_entry *entry = entries;
@@ -451,7 +456,7 @@ __init static int __append_e820_table(struct boot_e820_entry *entries, u32 nr_en 
		u64 end   = start + size-1;

		u32 type  = entry->type;



		/* Ignore the entry on 64-bit overflow: */

		/* Ignore the remaining entries on 64-bit overflow: */

		if (start > end && likely(size))

			return -1;
@@ -463,24 +468,6 @@ __init static int __append_e820_table(struct boot_e820_entry *entries, u32 nr_en 
	return 0;

}



/*

 * Copy the BIOS E820 map into a safe place.

 *

 * Sanity-check it while we're at it..

 *

 * If we're lucky and live on a modern system, the setup code

 * will have given us a memory map that we can use to properly

 * set up memory.  If we aren't, we'll fake a memory map.

 */

__init static int append_e820_table(struct boot_e820_entry *entries, u32 nr_entries)

{

	/* Only one memory region (or negative)? Ignore it */

	if (nr_entries < 2)

		return -1;



	return __append_e820_table(entries, nr_entries);

}



__init static u64

__e820__range_update(struct e820_table *table, u64 start, u64 size, enum e820_type old_type, enum e820_type new_type)

{
@@ -754,7 +741,7 @@ __init void e820__memory_setup_extended(u64 phys_addr, u32 data_len) 
	entries = sdata->len / sizeof(*extmap);

	extmap = (struct boot_e820_entry *)(sdata->data);



	__append_e820_table(extmap, entries);

	append_e820_table(extmap, entries);

	e820__update_table(e820_table);



	memcpy(e820_table_kexec, e820_table, sizeof(*e820_table_kexec));