linux-kernel - Re: [RFC PATCH v2 3/3] resource, crash: Make kexec_file

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Date:   Fri, 28 Apr 2023 07:10:02 +0000
From:   "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To:     Jane Chu <jane.chu@...cle.com>, "x86@...nel.org" <x86@...nel.org>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yasunori Gotou (Fujitsu)" <y-goto@...itsu.com>,
        "Xiao Yang (Fujitsu)" <yangx.jy@...itsu.com>,
        "Shiyang Ruan (Fujitsu)" <ruansy.fnst@...itsu.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Takashi Iwai <tiwai@...e.de>, Baoquan He <bhe@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Sean Christopherson <seanjc@...gle.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Raul E Rangel <rrangel@...omium.org>,
        Colin Foster <colin.foster@...advantage.com>,
        Vishal Verma <vishal.l.verma@...el.com>
Subject: Re: [RFC PATCH v2 3/3] resource, crash: Make kexec_file_load support
 pmem

Jane,


On 28/04/2023 04:41, Jane Chu wrote:
>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>> index cdd92ab43cda..dc9d03083565 100644
>> --- a/arch/x86/kernel/crash.c
>> +++ b/arch/x86/kernel/crash.c
>> @@ -178,6 +178,7 @@ static struct crash_mem *fill_up_crash_elf_data(void)
>>       if (!nr_ranges)
>>           return NULL;
>> +    walk_pmem_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
> 
> So this will overwrite 'nr_ranges' produced by the previous walk_system_ram_res() call, sure it's correct?


It depends on how the callback walk_system_ram_res() handle 'nr_ranges', so it's safe for this changes IMHO.

163 static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
164 {
165         unsigned int *nr_ranges = arg;
166
167         (*nr_ranges)++;
168         return 0;
169 }
170
171 /* Gather all the required information to prepare elf headers for ram regions */
172 static struct crash_mem *fill_up_crash_elf_data(void)
173 {
174         unsigned int nr_ranges = 0;
175         struct crash_mem *cmem;
176
177         walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
178         if (!nr_ranges)
179                 return NULL;
180
181         walk_pmem_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);

At last, nr_ranges = #ram_res + #pmem_res.

Thanks
Zhijian

> 
> Regards,
> -jane