From: ebiederm@xmission.com (Eric W. Biederman)
To: Hari Bathini <hbathini@linux.ibm.com>
Cc: Joonsoo Kim <js1304@gmail.com>,
kernel-team@lge.com, Michal Hocko <mhocko@suse.com>,
Minchan Kim <minchan@kernel.org>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
Rik van Riel <riel@surriel.com>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
LKML <linux-kernel@vger.kernel.org>,
Christian Koenig <christian.koenig@amd.com>,
Christoph Hellwig <hch@infradead.org>,
Linux Memory Management List <linux-mm@kvack.org>,
Huang Rui <ray.huang@amd.com>,
Kexec Mailing List <kexec@lists.infradead.org>,
Pavel Machek <pavel@ucw.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Laura Abbott <labbott@redhat.com>,
Mel Gorman <mgorman@techsingularity.net>,
Roman Gushchin <guro@fb.com>, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [RFC][PATCH] kexec: Teach indirect pages how to live in high memory
Date: Tue, 05 May 2020 13:39:16 -0500 [thread overview]
Message-ID: <87sggekyzv.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <54a53bfe-6929-2790-9b1d-943e9f47cd62@linux.ibm.com> (Hari Bathini's message of "Tue, 5 May 2020 23:14:32 +0530")
Hari Bathini <hbathini@linux.ibm.com> writes:
> On 05/05/20 3:29 am, Eric W. Biederman wrote:
>>
>> Recently a patch was proposed to kimage_alloc_page to slightly alter
>> the logic of how pages allocated with incompatible flags were
>> detected. The logic was being altered because the semantics of the
>> page alloctor were changing yet again.
>>
>> Looking at that case I realized that there is no reason for it to even
>> exist. Either the indirect page allocations and the source page
>> allocations could be separated out, or I could do as I am doing now
>> and simply teach the indirect pages to live in high memory.
>>
>> This patch replaced pointers of type kimage_entry_t * with a new type
>> kimage_entry_pos_t. This new type holds the physical address of the
>> indirect page and the offset within that page of the next indirect
>> entry to write. A special constant KIMAGE_ENTRY_POS_INVALID is added
>> that kimage_image_pos_t variables that don't currently have a valid
>> may be set to.
>>
>> Two new functions kimage_read_entry and kimage_write_entry have been
>> provided to write entries in way that works if they live in high
>> memory.
>>
>> The now unnecessary checks to see if a destination entry is non-zero
>> and to increment it if so have been removed. For safety new indrect
>> pages are now cleared so we have a guarantee everything that has not
>> been used yet is zero. Along with this writing an extra trailing 0
>> entry has been removed, as it is known all trailing entries are now 0.
>>
>> With highmem support implemented for indirect pages
>> kimage_image_alloc_page has been updated to always allocate
>> GFP_HIGHUSER pages, and handling of pages with different
>> gfp flags has been removed.
>>
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>
> Eric, the patch failed with data access exception on ppc64. Using the below patch on top
> got me going...
Doh! Somehow I thought I had put that logic or something equivalent
into kimage_write_entry and it appears I did not. I will see if I can
respin the patch.
Thank you very much for testing.
Eric
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 45862fd..bef52f1 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -570,7 +570,12 @@ static int kimage_add_entry(struct kimage *image, kimage_entry_t entry)
> return -ENOMEM;
>
> ind_addr = page_to_boot_pfn(page) << PAGE_SHIFT;
> - kimage_write_entry(image->entry_pos, ind_addr | IND_INDIRECTION);
> +
> + /* If it is the first entry, handle it here */
> + if (!image->head)
> + image->head = ind_addr | IND_INDIRECTION;
> + else
> + kimage_write_entry(image->entry_pos, ind_addr | IND_INDIRECTION);
>
> clear_highpage(page);
>
> @@ -623,7 +628,11 @@ int __weak machine_kexec_post_load(struct kimage *image)
>
> void kimage_terminate(struct kimage *image)
> {
> - kimage_write_entry(image->entry_pos, IND_DONE);
> + /* This could be the only entry in case of kdump */
> + if (!image->head)
> + image->head = IND_DONE;
> + else
> + kimage_write_entry(image->entry_pos, IND_DONE);
> }
>
> #define for_each_kimage_entry(image, pos, entry) \
>
>
> Thanks
> Hari
next prev parent reply other threads:[~2020-05-05 18:43 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 3:26 [PATCH v2 00/10] change the implementation of the PageHighMem() js1304
2020-04-29 3:26 ` [PATCH v2 01/10] mm/page-flags: introduce PageHighMemZone() js1304
2020-04-29 3:26 ` [PATCH v2 02/10] drm/ttm: separate PageHighMem() and PageHighMemZone() use case js1304
2020-04-29 3:26 ` [PATCH v2 03/10] kexec: " js1304
2020-05-01 14:03 ` Eric W. Biederman
2020-05-04 3:10 ` Joonsoo Kim
2020-05-04 14:03 ` Eric W. Biederman
2020-05-04 21:59 ` [RFC][PATCH] kexec: Teach indirect pages how to live in high memory Eric W. Biederman
2020-05-05 17:44 ` Hari Bathini
2020-05-05 18:39 ` Eric W. Biederman [this message]
2020-10-09 1:35 ` Joonsoo Kim
2020-05-06 5:23 ` [PATCH v2 03/10] kexec: separate PageHighMem() and PageHighMemZone() use case Joonsoo Kim
2020-04-29 3:26 ` [PATCH v2 04/10] power: " js1304
2020-05-01 12:22 ` Christoph Hellwig
2020-05-04 3:01 ` Joonsoo Kim
2020-04-29 3:26 ` [PATCH v2 05/10] mm/gup: " js1304
2020-05-01 12:24 ` Christoph Hellwig
2020-05-04 3:02 ` Joonsoo Kim
2020-04-29 3:26 ` [PATCH v2 06/10] mm/hugetlb: " js1304
2020-05-01 12:26 ` Christoph Hellwig
2020-05-04 3:03 ` Joonsoo Kim
2020-04-29 3:26 ` [PATCH v2 07/10] mm: " js1304
2020-05-01 12:30 ` Christoph Hellwig
2020-05-04 3:08 ` Joonsoo Kim
2020-04-29 3:26 ` [PATCH v2 08/10] mm/page_alloc: correct the use of is_highmem_idx() js1304
2020-04-29 3:26 ` [PATCH v2 09/10] mm/migrate: replace PageHighMem() with open-code js1304
2020-04-29 3:26 ` [PATCH v2 10/10] mm/page-flags: change the implementation of the PageHighMem() js1304
2020-04-30 1:47 ` [PATCH v2 00/10] " Andrew Morton
2020-05-01 10:52 ` Joonsoo Kim
2020-05-01 10:55 ` Christoph Hellwig
2020-05-01 12:15 ` Joonsoo Kim
2020-05-01 12:34 ` Christoph Hellwig
2020-05-04 3:09 ` Joonsoo Kim
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