Re: [PATCH] To crash dump, we need keep other memory type exceptE820_RAM, because other type come from BIOS or firmware is used by othercode(for example: PCI_MMCONFIG).
From: Paul Gortmaker
Date: Fri Nov 02 2012 - 11:10:33 EST
[RE: [PATCH] To crash dump, we need keep other memory type except E820_RAM, because other type come from BIOS or firmware is used by other code(for example: PCI_MMCONFIG).] On 01/11/2012 (Thu 08:49) Zhang, Jun wrote:
> Hello, Anvin
>
> Thank for your advice.
>
> Hello, All
>
> the next patch is made by 2), please review it. Thanks!
>
> Subject: [PATCH] When we are doing a crash dump, we still need non-E820_RAM
> memory information in order to do I/O. So only remove all
> RAM ranges which need to be dumped.
It is typical to do a "short log" in the subject, and then a "long log"
in what would be the following paragraph, i.e.
---------
Subject: crash dump: don't delete non-E820_RAM during init
Currently we delete the non-E820_RAM, which causes <describe the end
user symptoms here -- i.e. how things visibly break>
This happens because <describe the underlying technical reason
that causes the problem>
We can fix this by doing <describe the non-obvious aspects of your
change and why it is the right way to fix the problem>
---------
This "rule of three" is a good way to write commit logs. Just remember
(1)symptoms, (2)underlying problem, (3)how best to fix it.
Also, ...
>
> Signed-off-by: jzha144 <jun.zhang@xxxxxxxxx>
> ---
> arch/x86/kernel/e820.c | 8 --------
> arch/x86/kernel/setup.c | 22 ++++++++++++++++++++++
> 2 files changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index df06ade..0bc1687 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -844,14 +844,6 @@ static int __init parse_memmap_opt(char *p)
> return -EINVAL;
>
> if (!strncmp(p, "exactmap", 8)) {
> -#ifdef CONFIG_CRASH_DUMP
> - /*
> - * If we are doing a crash dump, we still need to know
> - * the real mem size before original memory map is
> - * reset.
> - */
> - saved_max_pfn = e820_end_of_ram_pfn();
> -#endif
> e820.nr_map = 0;
> userdef = 1;
> return 0;
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index ca45696..5eb178b 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -480,6 +480,25 @@ static void __init e820_reserve_setup_data(void)
> e820_print_map("reserve setup_data");
> }
>
> +#ifdef CONFIG_CRASH_DUMP
> +static void __init e820_crashdump_remove_ram(void)
> +{
... if you move this ifdef/endif within the { } of the function, then
we'll have one less ugly ifdef set below at the call site.
I'll leave the real technical review for Peter, who understands this
area better than I ever will.
Thanks,
Paul.
--
> + /*
> + * We are doing a crash dump, so remove all RAM ranges
> + * as they are the ones that need to be dumped.
> + * We still need all non-RAM information in order to do I/O.
> + */
> + /* NOTE: if you use old kexec, please remove memmap=exactmap
> + * which remove all ranges, not only RAM ranges.
> + */
> + saved_max_pfn = e820_end_of_ram_pfn();
> + e820_remove_range(0, ULLONG_MAX, E820_RAM, 1);
> + sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
> + printk(KERN_INFO "crash dump non-RAM map:\n");
> + e820_print_map("crash_dump");
> +}
> +#endif
> +
> static void __init memblock_x86_reserve_range_setup_data(void)
> {
> struct setup_data *data;
> @@ -751,6 +770,9 @@ void __init setup_arch(char **cmdline_p)
> parse_setup_data();
> /* update the e820_saved too */
> e820_reserve_setup_data();
> +#ifdef CONFIG_CRASH_DUMP
> + e820_crashdump_remove_ram();
> +#endif
>
> copy_edd();
>
> --
> 1.7.6
>
> Best Regards!
>
> Jun Zhang
> Inet: 8821-4273
> Dir.Tel: 86-21-6116-4273
> Email: jun.zhang@xxxxxxxxx
>
>
> -----Original Message-----
> From: H. Peter Anvin [mailto:hpa@xxxxxxxxx]
> Sent: Thursday, November 01, 2012 12:20 PM
> To: Zhang, Jun
> Cc: Thomas Gleixner; Ingo Molnar; x86@xxxxxxxxxx; Andrew Morton; Fleming, Matt; Paul Gortmaker; linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [PATCH] To crash dump, we need keep other memory type except E820_RAM, because other type come from BIOS or firmware is used by other code(for example: PCI_MMCONFIG).
>
> 2) would make most sense to me, but I'd be okay with 3) as well.
>
> "Zhang, Jun" <jun.zhang@xxxxxxxxx> wrote:
>
> >Hello, Anvin
> >
> >I want to explain why I modify in this place. In kexec, it pass three
> >parameters, memmap=exactmap memmap=544K@64K memmap=64964K@32768K I
> >think my patch modify the least code.
> >Actually, there are some choise to fix it.
> >1) my patch.
> >2) modify kexec, only pass two parameters -- memmap=544K@64K
> >memmap=64964K@32768K, in kernel setup_memory_map, we can remove RAM
> >range.
> >3) add extra optional, like memmap=REMOVERAM
> >
> >Which one do you like? Maybe you have better solution, please share it.
> >Thanks!
> >
> >Best Regards!
> >
> >Jun Zhang
> >Inet: 8821-4273
> >Dir.Tel: 86-21-6116-4273
> >Email: jun.zhang@xxxxxxxxx
> >
> >-----Original Message-----
> >From: H. Peter Anvin [mailto:hpa@xxxxxxxxx]
> >Sent: Wednesday, October 31, 2012 1:39 PM
> >To: Zhang, Jun
> >Cc: Thomas Gleixner; Ingo Molnar; x86@xxxxxxxxxx; Andrew Morton;
> >Fleming, Matt; Paul Gortmaker; linux-kernel@xxxxxxxxxxxxxxx
> >Subject: Re: [PATCH] To crash dump, we need keep other memory type
> >except E820_RAM, because other type come from BIOS or firmware is used
> >by other code(for example: PCI_MMCONFIG).
> >
> >On 10/30/2012 10:22 PM, Zhang, Jun wrote:
> >> Hello, Anvin
> >> You are right. Thanks!
> >>
> >> Hello, All
> >> Please review it again. Thanks!
> >>
> >> From bf7506ac7e9ce0df0b915164dbb7a6d858ef2e40 Mon Sep 17 00:00:00
> >> 2001
> >> From: jzha144 <jun.zhang@xxxxxxxxx>
> >> Date: Wed, 31 Oct 2012 08:51:18 +0800
> >> Subject: [PATCH] When we are doing a crash dump, we still need
> >non-E820_RAM
> >> memory type address information in order to do I/O. so only
> >> remove all RAM ranges which need to be dumped.
> >>
> >> Signed-off-by: jzha144 <jun.zhang@xxxxxxxxx>
> >> ---
> >> arch/x86/kernel/e820.c | 9 +++++++++
> >> 1 files changed, 9 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index
> >> df06ade..77be839 100644
> >> --- a/arch/x86/kernel/e820.c
> >> +++ b/arch/x86/kernel/e820.c
> >> @@ -851,6 +851,15 @@ static int __init parse_memmap_opt(char *p)
> >> * reset.
> >> */
> >> saved_max_pfn = e820_end_of_ram_pfn();
> >> +
> >> + /*
> >> + * We are doing a crash dump, so remove all RAM ranges
> >> + * as they are the ones that need to be dumped.
> >> + * We still need all non-RAM information in order to do I/O.
> >> + */
> >> + e820_remove_range(0, ULLONG_MAX, E820_RAM, 1);
> >> + userdef = 1;
> >> + return 0;
> >> #endif
> >> e820.nr_map = 0;
> >> userdef = 1;
> >>
> >
> >The code is still wrong...
> >
> > -hpa
> >
> >
> >--
> >H. Peter Anvin, Intel Open Source Technology Center I work for Intel.
> >I don't speak on their behalf.
>
> --
> Sent from my mobile phone. Please excuse brevity and lack of formatting.
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