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Date: Sat, 18 Apr 2009 01:33:24 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Ingo Molnar <mingo@...e.hu>,
Jesse Barnes <jbarnes@...tuousgeek.org>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-pci@...r.kernel.org, yannick.roehlly@...e.fr
Subject: Re: [PATCH] x86/pci: make pci_mem_start to be aligned only -v4
Linus Torvalds wrote:
>
> On Thu, 16 Apr 2009, Yinghai Lu wrote:
>> please check.
>>
>> [PATCH] x86/pci: make pci_mem_start to be aligned only -v4
>
> I like the approach. That said, I think that rather than do the "modify
> the e820 array" thing, why not just do it in the in the resource tree, and
> do it at "e820_reserve_resources_late()" time?
>
> IOW, something like this.
>
> TOTALLY UNTESTED! The point is to take all RAM resources we haev, and
> _after_ we've added all the resources we've seen in the E820 tree, we then
> _also_ try to add fake reserved entries for any "round up to X" at the end
> of the RAM resources.
>
> NOTE! I really didn't want to use "reserve_region_with_split()". I didn't
> want to recurse into any conflicting resources, I really wanted to just do
> the other failure cases.
>
> THIS PATCH IS NOT MEANT TO BE USED. Just a rough "almost like this" kind
> of thing. That includes the rough draft of how much to round things up to
> based on where the end of RAM region is etc. I'm really throwing this out
> more as a "wouldn't this be a readable way to handle any missing reserved
> entries" kind of thing..
>
> Linus
>
> ---
> arch/x86/kernel/e820.c | 34 ++++++++++++++++++++++++++++++++++
> 1 files changed, 34 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index ef2c356..e8b8d33 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -1370,6 +1370,23 @@ void __init e820_reserve_resources(void)
> }
> }
>
> +/* How much should we pad RAM ending depending on where it is? */
> +static unsigned long ram_alignment(resource_size_t pos)
> +{
> + unsigned long mb = pos >> 20;
> +
> + /* To 64kB in the first megabyte */
> + if (!mb)
> + return 64*1024;
> +
> + /* To 1MB in the first 16MB */
> + if (mb < 16)
> + return 1024*1024;
> +
> + /* To 32MB for anything above that */
> + return 32*1024*1024;
> +}
> +
> void __init e820_reserve_resources_late(void)
> {
> int i;
> @@ -1381,6 +1398,23 @@ void __init e820_reserve_resources_late(void)
> insert_resource_expand_to_fit(&iomem_resource, res);
> res++;
> }
> +
> + /*
> + * Try to bump up RAM regions to reasonable boundaries to
> + * avoid stolen RAM
> + */
> + for (i = 0; i < e820.nr_map; i++) {
> + struct e820entry *entry = &e820_saved.map[i];
> + resource_size_t start, end;
> +
> + if (entry->type != E820_RAM)
> + continue;
> + start = entry->addr + entry->size;
> + end = round_up(start, ram_alignment(start));
> + if (start == end)
> + continue;
> + reserve_region_with_split(&iomem_resource, start, end, "RAM buffer");
> + }
> }
>
> char *__init default_machine_specific_memory_setup(void)
except need to change
> + reserve_region_with_split(&iomem_resource, start, end, "RAM buffer");
==> > + reserve_region_with_split(&iomem_resource, start, end - 1, "RAM buffer");
it will make sure dynmical allocating code will not use those range.
and could make e820_setup_gap much simple.
---
arch/x86/kernel/e820.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
Index: linux-2.6/arch/x86/kernel/e820.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/e820.c
+++ linux-2.6/arch/x86/kernel/e820.c
@@ -635,14 +635,12 @@ __init void e820_setup_gap(void)
#endif
/*
- * See how much we want to round up: start off with
- * rounding to the next 1MB area.
+ * e820_reserve_resources_late will protect stolen RAM
+ * so just round it to 1M
*/
round = 0x100000;
- while ((gapsize >> 4) > round)
- round += round;
- /* Fun with two's complement */
- pci_mem_start = (gapstart + round) & -round;
+
+ pci_mem_start = roundup(gapstart, round);
printk(KERN_INFO
"Allocating PCI resources starting at %lx (gap: %lx:%lx)\n",
Ingo, can you put those two patches in tip?
YH
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