Messages in this thread | | | Subject | Re: [PATCH V4 2/3] arm64/mm/hotplug: Enable MEM_OFFLINE event handling | From | Gavin Shan <> | Date | Thu, 1 Oct 2020 09:57:04 +1000 |
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Hi Anshuman,
On 9/29/20 11:54 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. While here, also call out the first section being attempted > for offline or got offlined. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Marc Zyngier <maz@kernel.org> > Cc: Steve Capper <steve.capper@arm.com> > Cc: Mark Brown <broonie@kernel.org> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/mm/mmu.c | 29 +++++++++++++++++++++++++++-- > 1 file changed, 27 insertions(+), 2 deletions(-) >
This looks good to me except a nit and it can be improved if that looks reasonable and only when you get a chance for respin.
Reviewed-by: Gavin Shan <gshan@redhat.com>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 4e70f4fea06c..90a30f5ebfc0 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1482,13 +1482,38 @@ 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) { > + unsigned long start = PFN_PHYS(pfn); > + unsigned long end = start + (1UL << PA_SECTION_SHIFT); > + > ms = __pfn_to_section(pfn); > - if (early_section(ms)) > + if (!early_section(ms)) > + continue; > +
The discussion here is irrelevant to this patch itself. It seems early_section() is coarse, which means all memory detected during boot time won't be hotpluggable?
> + if (action == MEM_GOING_OFFLINE) { > + pr_warn("Boot memory [%lx %lx] offlining attempted\n", start, end); > return NOTIFY_BAD; > + } else if (action == MEM_OFFLINE) { > + /* > + * 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 [%lx %lx] offlined\n", start, end); > + > + /* > + * 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; > } >
I think NOTIFY_BAD is returned for MEM_OFFLINE wouldn't be a bad idea, even the core isn't handling the errno. With this, the code can be simplified. However, it's not a big deal and you probably evaluate and change when you need another respin:
pr_warn("Boot memory [%lx %lx] %s\n", (action == MEM_GOING_OFFLINE) ? "offlining attempted" : "offlined", start, end); return NOTIFY_BAD;
Cheers, Gavin
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