lkml.org 
[lkml]   [2017]   [Jan]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 20/50] x86/boot/e820: Rename memblock_x86_fill() to e820__memblock_setup() and improve the explanations
Date
So memblock_x86_fill() is another E820 code misnomer:

- nothing in its name tells us that it's part of the E820 subsystem ...

- The 'fill' wording is ambiguous and doesn't tell us whether it's a single
entry or some process - while the _real_ purpose of the function is hidden,
which is to do a complete setup of the (platform independent) memblock regions.

So rename it accordingly, to e820__memblock_setup().

Also translate this incomprehensible and misleading comment:

/*
* EFI may have more than 128 entries
* We are safe to enable resizing, beause memblock_x86_fill()
* is rather later for x86
*/
memblock_allow_resize();

The worst aspect of this comment isn't even the sloppy typos, but that it
casually mentions a '128' number with no explanation, which makes one lead
to the assumption that this is related to the well-known limit of a maximum
of 128 E820 entries passed via legacy bootloaders.

But no, the _real_ meaning of 128 here is that of the memblock subsystem,
which too happens to have a 128 entries limit for very early memblock
regions (which is unrelated to E820), via INIT_MEMBLOCK_REGIONS ...

So change the comment to a more comprehensible version:

/*
* The bootstrap memblock region count maximum is 128 entries
* (INIT_MEMBLOCK_REGIONS), but EFI might pass us more E820 entries
* than that - so allow memblock resizing.
*
* This is safe, because this call happens pretty late during x86 setup,
* so we know about reserved memory regions already. (This is important
* so that memblock resizing does no stomp over reserved areas.)
*/
memblock_allow_resize();

No change in functionality.

Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Jackson <pj@sgi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/e820/api.h | 2 +-
arch/x86/kernel/e820.c | 14 +++++++++-----
arch/x86/kernel/setup.c | 4 ++--
3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/e820/api.h b/arch/x86/include/asm/e820/api.h
index 2c336d8a8593..01698548fbc8 100644
--- a/arch/x86/include/asm/e820/api.h
+++ b/arch/x86/include/asm/e820/api.h
@@ -21,7 +21,7 @@ extern void parse_e820_ext(u64 phys_addr, u32 data_len);
extern unsigned long e820_end_of_ram_pfn(void);
extern unsigned long e820_end_of_low_ram_pfn(void);
extern u64 early_reserve_e820(u64 sizet, u64 align);
-extern void memblock_x86_fill(void);
+extern void e820__memblock_setup(void);
extern void memblock_find_dma_reserve(void);
extern void finish_e820_parsing(void);
extern void e820_reserve_resources(void);
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 624190fe86a7..b8e216b3957a 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1138,15 +1138,19 @@ void __init e820__memory_setup(void)
e820_print_map(who);
}

-void __init memblock_x86_fill(void)
+void __init e820__memblock_setup(void)
{
int i;
u64 end;

/*
- * EFI may have more than 128 entries
- * We are safe to enable resizing, beause memblock_x86_fill()
- * is rather later for x86
+ * The bootstrap memblock region count maximum is 128 entries
+ * (INIT_MEMBLOCK_REGIONS), but EFI might pass us more E820 entries
+ * than that - so allow memblock resizing.
+ *
+ * This is safe, because this call happens pretty late during x86 setup,
+ * so we know about reserved memory regions already. (This is important
+ * so that memblock resizing does no stomp over reserved areas.)
*/
memblock_allow_resize();

@@ -1163,7 +1167,7 @@ void __init memblock_x86_fill(void)
memblock_add(ei->addr, ei->size);
}

- /* throw away partial pages */
+ /* Throw away partial pages: */
memblock_trim_memory(PAGE_SIZE);

memblock_dump_all();
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index f905430d7b04..838e4b5707ae 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1109,7 +1109,7 @@ void __init setup_arch(char **cmdline_p)
early_alloc_pgt_buf();

/*
- * Need to conclude brk, before memblock_x86_fill()
+ * Need to conclude brk, before e820__memblock_setup()
* it could use memblock_find_in_range, could overlap with
* brk area.
*/
@@ -1118,7 +1118,7 @@ void __init setup_arch(char **cmdline_p)
cleanup_highmap();

memblock_set_current_limit(ISA_END_ADDRESS);
- memblock_x86_fill();
+ e820__memblock_setup();

reserve_bios_regions();

--
2.7.4
\
 
 \ /
  Last update: 2017-01-28 23:22    [W:0.214 / U:17.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site