linux-kernel - Re: [PATCH] x86/e820: don't merge consecutive E820

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Date:   Fri, 14 Oct 2016 07:15:02 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        X86 ML <x86@...nel.org>, Dave Chinner <david@...morbit.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Jeff Moyer <jmoyer@...hat.com>, Zhang Yi <yizhan@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/e820: don't merge consecutive E820_PRAM ranges

On Wed, Oct 12, 2016 at 11:01 AM, Dan Williams <dan.j.williams@...el.com> wrote:
> Commit 917db484dc6a "x86/boot: Fix kdump, cleanup aborted E820_PRAM
> max_pfn manipulation" fixed up the broken manipulations of max_pfn in
> the presence of E820_PRAM ranges. However, it also broke the
> sanitize_e820_map() support for not merging E820_PRAM ranges.
> Re-introduce the enabling to keep resource boundaries between
> consecutive defined ranges. Otherwise, for example, an environment that
> boots with memmap=2G!8G,2G!10G will end up with a single 4G /dev/pmem0
> device instead of a /dev/pmem0 and /dev/pmem1 device 2G in size.
>
> Cc: <stable@...r.kernel.org>
> Cc: Zhang Yi <yizhan@...hat.com>
> Cc: Jeff Moyer <jmoyer@...hat.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Reported-by: Dave Chinner <david@...morbit.com>
> Fixes: 917db484dc6a ("x86/boot: Fix kdump, cleanup aborted E820_PRAM max_pfn manipulation")
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  arch/x86/kernel/e820.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index b85fe5f91c3f..90e8dde3ec26 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -350,7 +350,7 @@ int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
>                  * continue building up new bios map based on this
>                  * information
>                  */
> -               if (current_type != last_type) {
> +               if (current_type != last_type || current_type == E820_PRAM) {
>                         if (last_type != 0)      {
>                                 new_bios[new_bios_entry].size =
>                                         change_point[chgidx]->addr - last_addr;
>

Hi Ingo, can you grab this one for 4.9-rc1?  The regression is now
making its way to the -stable branches, so this fix is needed there
now as well.

Let me know, I can also just take it through libnvdimm.git with an ack.