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From: Hari Bathini <hbathini@linux.ibm.com>
To: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Pingfan Liu <piliu@redhat.com>, Nayna Jain <nayna@linux.ibm.com>,
	Kexec-ml <kexec@lists.infradead.org>,
	Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
	Mimi Zohar <zohar@linux.ibm.com>,
	lkml <linux-kernel@vger.kernel.org>,
	linuxppc-dev <linuxppc-dev@ozlabs.org>,
	Sourabh Jain <sourabhjain@linux.ibm.com>,
	Petr Tesarik <ptesarik@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
	Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH v3 10/12] ppc64/kexec_file: prepare elfcore header for crashing kernel
Date: Fri, 17 Jul 2020 02:37:56 +0530	[thread overview]
Message-ID: <929db6fe-b221-a514-8ea1-93227f8d47b0@linux.ibm.com> (raw)
In-Reply-To: <87tuy88ai7.fsf@morokweng.localdomain>



On 16/07/20 7:52 am, Thiago Jung Bauermann wrote:
> 
> Hari Bathini <hbathini@linux.ibm.com> writes:
> 
>>  /**
>> + * get_crash_memory_ranges - Get crash memory ranges. This list includes
>> + *                           first/crashing kernel's memory regions that
>> + *                           would be exported via an elfcore.
>> + * @mem_ranges:              Range list to add the memory ranges to.
>> + *
>> + * Returns 0 on success, negative errno on error.
>> + */
>> +static int get_crash_memory_ranges(struct crash_mem **mem_ranges)
>> +{
>> +	struct memblock_region *reg;
>> +	struct crash_mem *tmem;
>> +	int ret;
>> +
>> +	for_each_memblock(memory, reg) {
>> +		u64 base, size;
>> +
>> +		base = (u64)reg->base;
>> +		size = (u64)reg->size;
>> +
>> +		/* Skip backup memory region, which needs a separate entry */
>> +		if (base == BACKUP_SRC_START) {
>> +			if (size > BACKUP_SRC_SIZE) {
>> +				base = BACKUP_SRC_END + 1;
>> +				size -= BACKUP_SRC_SIZE;
>> +			} else
>> +				continue;
>> +		}
>> +
>> +		ret = add_mem_range(mem_ranges, base, size);
>> +		if (ret)
>> +			goto out;
>> +
>> +		/* Try merging adjacent ranges before reallocation attempt */
>> +		if ((*mem_ranges)->nr_ranges == (*mem_ranges)->max_nr_ranges)
>> +			sort_memory_ranges(*mem_ranges, true);
>> +	}
>> +
>> +	/* Reallocate memory ranges if there is no space to split ranges */
>> +	tmem = *mem_ranges;
>> +	if (tmem && (tmem->nr_ranges == tmem->max_nr_ranges)) {
>> +		tmem = realloc_mem_ranges(mem_ranges);
>> +		if (!tmem)
>> +			goto out;
>> +	}
>> +
>> +	/* Exclude crashkernel region */
>> +	ret = crash_exclude_mem_range(tmem, crashk_res.start, crashk_res.end);
>> +	if (ret)
>> +		goto out;
>> +
>> +	ret = add_rtas_mem_range(mem_ranges);
>> +	if (ret)
>> +		goto out;
>> +
>> +	ret = add_opal_mem_range(mem_ranges);
>> +	if (ret)
>> +		goto out;
> 
> Maybe I'm confused, but don't you add the RTAS and OPAL regions as
> usable memory for the crashkernel? In that case they shouldn't show up
> in the core file.

kexec-tools does the same thing. I am not endorsing it but I was trying to stay
in parity to avoid breaking any userspace tools/commands. But as you rightly
pointed, this is NOT right. The right thing to do, to get the rtas/opal data at
the time of crash, is to have a backup region for them just like we have for
the first 64K memory. I was hoping to do that later.

Will check how userspace tools respond to dropping these regions. If that makes
the tools unhappy, will retain the regions with a FIXME. Sorry about the confusion.

Thanks
Hari

WARNING: multiple messages have this Message-ID (diff)
From: Hari Bathini <hbathini@linux.ibm.com>
To: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Pingfan Liu <piliu@redhat.com>, Petr Tesarik <ptesarik@suse.cz>,
	Nayna Jain <nayna@linux.ibm.com>,
	Kexec-ml <kexec@lists.infradead.org>,
	Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
	Mimi Zohar <zohar@linux.ibm.com>,
	lkml <linux-kernel@vger.kernel.org>,
	linuxppc-dev <linuxppc-dev@ozlabs.org>,
	Sourabh Jain <sourabhjain@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
	Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH v3 10/12] ppc64/kexec_file: prepare elfcore header for crashing kernel
Date: Fri, 17 Jul 2020 02:37:56 +0530	[thread overview]
Message-ID: <929db6fe-b221-a514-8ea1-93227f8d47b0@linux.ibm.com> (raw)
In-Reply-To: <87tuy88ai7.fsf@morokweng.localdomain>



On 16/07/20 7:52 am, Thiago Jung Bauermann wrote:
> 
> Hari Bathini <hbathini@linux.ibm.com> writes:
> 
>>  /**
>> + * get_crash_memory_ranges - Get crash memory ranges. This list includes
>> + *                           first/crashing kernel's memory regions that
>> + *                           would be exported via an elfcore.
>> + * @mem_ranges:              Range list to add the memory ranges to.
>> + *
>> + * Returns 0 on success, negative errno on error.
>> + */
>> +static int get_crash_memory_ranges(struct crash_mem **mem_ranges)
>> +{
>> +	struct memblock_region *reg;
>> +	struct crash_mem *tmem;
>> +	int ret;
>> +
>> +	for_each_memblock(memory, reg) {
>> +		u64 base, size;
>> +
>> +		base = (u64)reg->base;
>> +		size = (u64)reg->size;
>> +
>> +		/* Skip backup memory region, which needs a separate entry */
>> +		if (base == BACKUP_SRC_START) {
>> +			if (size > BACKUP_SRC_SIZE) {
>> +				base = BACKUP_SRC_END + 1;
>> +				size -= BACKUP_SRC_SIZE;
>> +			} else
>> +				continue;
>> +		}
>> +
>> +		ret = add_mem_range(mem_ranges, base, size);
>> +		if (ret)
>> +			goto out;
>> +
>> +		/* Try merging adjacent ranges before reallocation attempt */
>> +		if ((*mem_ranges)->nr_ranges == (*mem_ranges)->max_nr_ranges)
>> +			sort_memory_ranges(*mem_ranges, true);
>> +	}
>> +
>> +	/* Reallocate memory ranges if there is no space to split ranges */
>> +	tmem = *mem_ranges;
>> +	if (tmem && (tmem->nr_ranges == tmem->max_nr_ranges)) {
>> +		tmem = realloc_mem_ranges(mem_ranges);
>> +		if (!tmem)
>> +			goto out;
>> +	}
>> +
>> +	/* Exclude crashkernel region */
>> +	ret = crash_exclude_mem_range(tmem, crashk_res.start, crashk_res.end);
>> +	if (ret)
>> +		goto out;
>> +
>> +	ret = add_rtas_mem_range(mem_ranges);
>> +	if (ret)
>> +		goto out;
>> +
>> +	ret = add_opal_mem_range(mem_ranges);
>> +	if (ret)
>> +		goto out;
> 
> Maybe I'm confused, but don't you add the RTAS and OPAL regions as
> usable memory for the crashkernel? In that case they shouldn't show up
> in the core file.

kexec-tools does the same thing. I am not endorsing it but I was trying to stay
in parity to avoid breaking any userspace tools/commands. But as you rightly
pointed, this is NOT right. The right thing to do, to get the rtas/opal data at
the time of crash, is to have a backup region for them just like we have for
the first 64K memory. I was hoping to do that later.

Will check how userspace tools respond to dropping these regions. If that makes
the tools unhappy, will retain the regions with a FIXME. Sorry about the confusion.

Thanks
Hari

  reply	other threads:[~2020-07-16 21:08 UTC|newest]

Thread overview: 125+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-13 17:20 [PATCH v3 00/12] ppc64: enable kdump support for kexec_file_load syscall Hari Bathini
2020-07-13 17:20 ` Hari Bathini
2020-07-13 17:20 ` Hari Bathini
2020-07-13 17:20 ` [PATCH v3 01/12] kexec_file: allow archs to handle special regions while locating memory hole Hari Bathini
2020-07-13 17:20   ` Hari Bathini
2020-07-13 17:20   ` Hari Bathini
2020-07-14 21:00   ` Thiago Jung Bauermann
2020-07-14 21:00     ` Thiago Jung Bauermann
2020-07-14 21:00     ` Thiago Jung Bauermann
2020-07-13 17:21 ` [PATCH v3 02/12] powerpc/kexec_file: mark PPC64 specific code Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-16  1:49   ` Thiago Jung Bauermann
2020-07-16  1:49     ` Thiago Jung Bauermann
2020-07-16  1:49     ` Thiago Jung Bauermann
2020-07-17  4:46     ` Hari Bathini
2020-07-17  4:46       ` Hari Bathini
2020-07-17  4:46       ` Hari Bathini
2020-07-17 18:34       ` Thiago Jung Bauermann
2020-07-17 18:34         ` Thiago Jung Bauermann
2020-07-13 17:21 ` [PATCH v3 03/12] powerpc/kexec_file: add helper functions for getting memory ranges Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-14 23:49   ` Thiago Jung Bauermann
2020-07-14 23:49     ` Thiago Jung Bauermann
2020-07-14 23:49     ` Thiago Jung Bauermann
2020-07-16 21:08     ` Hari Bathini
2020-07-16 21:08       ` Hari Bathini
2020-07-17  4:32     ` Hari Bathini
2020-07-17  4:32       ` Hari Bathini
2020-07-17  4:32       ` Hari Bathini
2020-07-17 20:00       ` Hari Bathini
2020-07-17 20:00         ` Hari Bathini
2020-07-13 17:21 ` [PATCH v3 04/12] ppc64/kexec_file: avoid stomping memory used by special regions Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-15  2:39   ` Thiago Jung Bauermann
2020-07-15  2:39     ` Thiago Jung Bauermann
2020-07-15  2:39     ` Thiago Jung Bauermann
2020-07-16  5:58     ` Thiago Jung Bauermann
2020-07-16  5:58       ` Thiago Jung Bauermann
2020-07-16  5:58       ` Thiago Jung Bauermann
2020-07-16 21:09     ` Hari Bathini
2020-07-16 21:09       ` Hari Bathini
2020-07-16 21:59       ` Thiago Jung Bauermann
2020-07-16 21:59         ` Thiago Jung Bauermann
2020-07-16 21:59         ` Thiago Jung Bauermann
2020-07-13 17:21 ` [PATCH v3 05/12] powerpc/drmem: make lmb walk a bit more flexible Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-13 17:21   ` Hari Bathini
2020-07-15  3:50   ` Thiago Jung Bauermann
2020-07-15  3:50     ` Thiago Jung Bauermann
2020-07-15  3:50     ` Thiago Jung Bauermann
2020-07-16 21:09     ` Hari Bathini
2020-07-16 21:09       ` Hari Bathini
2020-07-16 22:01       ` Thiago Jung Bauermann
2020-07-16 22:01         ` Thiago Jung Bauermann
2020-07-16 22:01         ` Thiago Jung Bauermann
2020-07-13 17:22 ` [PATCH v3 06/12] ppc64/kexec_file: restrict memory usage of kdump kernel Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-15 22:52   ` Thiago Jung Bauermann
2020-07-15 22:52     ` Thiago Jung Bauermann
2020-07-15 22:52     ` Thiago Jung Bauermann
2020-07-16 21:10     ` Hari Bathini
2020-07-16 21:10       ` Hari Bathini
2020-07-16 22:03       ` Thiago Jung Bauermann
2020-07-16 22:03         ` Thiago Jung Bauermann
2020-07-16 22:03         ` Thiago Jung Bauermann
2020-07-17  4:17         ` Hari Bathini
2020-07-17  4:17           ` Hari Bathini
2020-07-13 17:22 ` [PATCH v3 07/12] ppc64/kexec_file: add support to relocate purgatory Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-16  0:20   ` Thiago Jung Bauermann
2020-07-16  0:20     ` Thiago Jung Bauermann
2020-07-16  0:20     ` Thiago Jung Bauermann
2020-07-16 21:11     ` Hari Bathini
2020-07-16 21:11       ` Hari Bathini
2020-07-16 22:12       ` Thiago Jung Bauermann
2020-07-16 22:12         ` Thiago Jung Bauermann
2020-07-16 22:12         ` Thiago Jung Bauermann
2020-07-13 17:22 ` [PATCH v3 08/12] ppc64/kexec_file: setup the stack for purgatory Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-16  0:35   ` Thiago Jung Bauermann
2020-07-16  0:35     ` Thiago Jung Bauermann
2020-07-16  0:35     ` Thiago Jung Bauermann
2020-07-16  1:40   ` Thiago Jung Bauermann
2020-07-16  1:40     ` Thiago Jung Bauermann
2020-07-16  1:40     ` Thiago Jung Bauermann
2020-07-13 17:22 ` [PATCH v3 09/12] ppc64/kexec_file: setup backup region for kdump kernel Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-13 17:22   ` Hari Bathini
2020-07-16  1:38   ` Thiago Jung Bauermann
2020-07-16  1:38     ` Thiago Jung Bauermann
2020-07-16  1:38     ` Thiago Jung Bauermann
2020-07-16 21:10     ` Hari Bathini
2020-07-16 21:10       ` Hari Bathini
2020-07-16 22:06       ` Thiago Jung Bauermann
2020-07-16 22:06         ` Thiago Jung Bauermann
2020-07-16 22:06         ` Thiago Jung Bauermann
2020-07-13 17:23 ` [PATCH v3 10/12] ppc64/kexec_file: prepare elfcore header for crashing kernel Hari Bathini
2020-07-13 17:23   ` Hari Bathini
2020-07-13 17:23   ` Hari Bathini
2020-07-16  2:22   ` Thiago Jung Bauermann
2020-07-16  2:22     ` Thiago Jung Bauermann
2020-07-16  2:22     ` Thiago Jung Bauermann
2020-07-16 21:07     ` Hari Bathini [this message]
2020-07-16 21:07       ` Hari Bathini
2020-07-16 21:57       ` Thiago Jung Bauermann
2020-07-16 21:57         ` Thiago Jung Bauermann
2020-07-16 21:57         ` Thiago Jung Bauermann
2020-07-13 17:23 ` [PATCH v3 11/12] ppc64/kexec_file: add appropriate regions for memory reserve map Hari Bathini
2020-07-13 17:23   ` Hari Bathini
2020-07-13 17:23   ` Hari Bathini
2020-07-16  2:27   ` Thiago Jung Bauermann
2020-07-16  2:27     ` Thiago Jung Bauermann
2020-07-16  2:27     ` Thiago Jung Bauermann
2020-07-13 17:23 ` [PATCH v3 12/12] ppc64/kexec_file: fix kexec load failure with lack of memory hole Hari Bathini
2020-07-13 17:23   ` Hari Bathini
2020-07-13 17:23   ` Hari Bathini
2020-07-16  5:43   ` Thiago Jung Bauermann
2020-07-16  5:43     ` Thiago Jung Bauermann
2020-07-16  5:43     ` Thiago Jung Bauermann

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