[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <d4e90ed2-f348-0d80-b3d7-d156abe05a90@redhat.com>
Date: Wed, 23 Sep 2020 16:31:34 +1000
From: Gavin Shan <gshan@...hat.com>
To: Anshuman Khandual <anshuman.khandual@....com>,
linux-arm-kernel@...ts.infradead.org
Cc: Mark Rutland <mark.rutland@....com>, Will Deacon <will@...nel.com>,
catalin.marinas@....com, Steve Capper <steve.capper@....com>,
linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
Marc Zyngier <maz@...nel.org>, will@...nel.org
Subject: Re: [PATCH V3 2/3] arm64/mm/hotplug: Enable MEM_OFFLINE event
handling
Hi Anshuman,
On 9/21/20 10:05 PM, Anshuman Khandual wrote:
> This enables MEM_OFFLINE memory event handling. It will help intercept any
> possible error condition such as if boot memory some how still got offlined
> even after an explicit notifier failure, potentially by a future change in
> generic hot plug framework. This would help detect such scenarios and help
> debug further.
>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Steve Capper <steve.capper@....com>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
I'm not sure if it makes sense since MEM_OFFLINE won't be triggered
after NOTIFY_BAD is returned from MEM_GOING_OFFLINE. NOTIFY_BAD means
the whole offline process is stopped. It would be guranteed by generic
framework from syntax standpoint.
However, this looks good if MEM_OFFLINE is triggered without calling
into MEM_GOING_OFFLINE previously, but it would be a bug from generic
framework.
> arch/arm64/mm/mmu.c | 37 ++++++++++++++++++++++++++++++++-----
> 1 file changed, 32 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index df3b7415b128..6b171bd88bcf 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1482,13 +1482,40 @@ static int prevent_bootmem_remove_notifier(struct notifier_block *nb,
> unsigned long end_pfn = arg->start_pfn + arg->nr_pages;
> unsigned long pfn = arg->start_pfn;
>
> - if (action != MEM_GOING_OFFLINE)
> + if ((action != MEM_GOING_OFFLINE) && (action != MEM_OFFLINE))
> return NOTIFY_OK;
>
> - for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> - ms = __pfn_to_section(pfn);
> - if (early_section(ms))
> - return NOTIFY_BAD;
> + if (action == MEM_GOING_OFFLINE) {
> + for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> + ms = __pfn_to_section(pfn);
> + if (early_section(ms)) {
> + pr_warn("Boot memory offlining attempted\n");
> + return NOTIFY_BAD;
> + }
> + }
> + } else if (action == MEM_OFFLINE) {
> + for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> + ms = __pfn_to_section(pfn);
> + if (early_section(ms)) {
> +
> + /*
> + * This should have never happened. Boot memory
> + * offlining should have been prevented by this
> + * very notifier. Probably some memory removal
> + * procedure might have changed which would then
> + * require further debug.
> + */
> + pr_err("Boot memory offlined\n");
> +
> + /*
> + * Core memory hotplug does not process a return
> + * code from the notifier for MEM_OFFLINE event.
> + * Error condition has been reported. Report as
> + * ignored.
> + */
> + return NOTIFY_DONE;
> + }
> + }
> }
> return NOTIFY_OK;
> }
>
It's pretty much irrelevant comment if the patch doesn't make sense:
the logical block for MEM_GOING_OFFLINE would be reused by MEM_OFFLINE
as they looks similar except the return value and error message :)
Cheers,
Gavin
Powered by blists - more mailing lists