diff mbox series

[2/2] arm64: allow hotpluggable sections to be offlined

Message ID c5f96b483158871ff65377884955fb0106e43951.1602899443.git.sudaraja@codeaurora.org
State New, archived
Headers show
Series mm/memory_hotplug, arm64: allow certain bootmem sections to be offlinable | expand

Commit Message

Sudarshan Rajagopalan Oct. 17, 2020, 2:02 a.m. UTC
On receiving the MEM_GOING_OFFLINE notification, we disallow offlining of
any boot memory by checking if section_early or not. With the introduction
of SECTION_MARK_HOTPLUGGABLE, allow boot mem sections that are marked as
hotpluggable with this bit set to be offlined and removed. This now allows
certain boot mem sections to be offlined.

Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Gavin Shan <gshan@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
---
 arch/arm64/mm/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

David Hildenbrand Oct. 17, 2020, 7:34 a.m. UTC | #1
> Am 17.10.2020 um 04:03 schrieb Sudarshan Rajagopalan <sudaraja@codeaurora.org>:
> 
> On receiving the MEM_GOING_OFFLINE notification, we disallow offlining of
> any boot memory by checking if section_early or not. With the introduction
> of SECTION_MARK_HOTPLUGGABLE, allow boot mem sections that are marked as
> hotpluggable with this bit set to be offlined and removed. This now allows
> certain boot mem sections to be offlined.
> 

The check (notifier) is in arm64 code. I don‘t see why you cannot make such decisions completely in arm64 code? Why would you have to mark sections?

Also, I think I am missing from *where* the code that marks sections removable is even called? Who makes such decisions?

This feels wrong. 

> Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Gavin Shan <gshan@redhat.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Steven Price <steven.price@arm.com>
> Cc: Suren Baghdasaryan <surenb@google.com>
> ---
> arch/arm64/mm/mmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 75df62fea1b6..fb8878698672 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1487,7 +1487,7 @@ static int prevent_bootmem_remove_notifier(struct notifier_block *nb,
> 
>    for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
>        ms = __pfn_to_section(pfn);
> -        if (early_section(ms))
> +        if (early_section(ms) && !removable_section(ms))
>            return NOTIFY_BAD;
>    }
>    return NOTIFY_OK;
> -- 
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
Anshuman Khandual Oct. 19, 2020, 6:56 a.m. UTC | #2
On 10/17/2020 01:04 PM, David Hildenbrand wrote:
> 
>> Am 17.10.2020 um 04:03 schrieb Sudarshan Rajagopalan <sudaraja@codeaurora.org>:
>>
>> On receiving the MEM_GOING_OFFLINE notification, we disallow offlining of
>> any boot memory by checking if section_early or not. With the introduction
>> of SECTION_MARK_HOTPLUGGABLE, allow boot mem sections that are marked as
>> hotpluggable with this bit set to be offlined and removed. This now allows
>> certain boot mem sections to be offlined.
>>
> 
> The check (notifier) is in arm64 code. I don‘t see why you cannot make such decisions completely in arm64 code? Why would you have to mark sections?
> 
> Also, I think I am missing from *where* the code that marks sections removable is even called? Who makes such decisions?

From the previous patch.

+EXPORT_SYMBOL_GPL(mark_memory_hotpluggable);

> 
> This feels wrong. 
> 
>> Signed-off-by: Sudarshan Rajagopalan <sudaraja@codeaurora.org>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Gavin Shan <gshan@redhat.com>
>> Cc: Logan Gunthorpe <logang@deltatee.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Steven Price <steven.price@arm.com>
>> Cc: Suren Baghdasaryan <surenb@google.com>
>> ---
>> arch/arm64/mm/mmu.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 75df62fea1b6..fb8878698672 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1487,7 +1487,7 @@ static int prevent_bootmem_remove_notifier(struct notifier_block *nb,
>>
>>    for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
>>        ms = __pfn_to_section(pfn);
>> -        if (early_section(ms))
>> +        if (early_section(ms) && !removable_section(ms))

Till challenges related to boot memory removal on arm64 platform get
resolved, no portion of boot memory can be offlined. Let alone via a
driver making such decisions.

>>            return NOTIFY_BAD;
>>    }
>>    return NOTIFY_OK;
>> -- 
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>>
> 
>
diff mbox series

Patch

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 75df62fea1b6..fb8878698672 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1487,7 +1487,7 @@  static int prevent_bootmem_remove_notifier(struct notifier_block *nb,
 
 	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
 		ms = __pfn_to_section(pfn);
-		if (early_section(ms))
+		if (early_section(ms) && !removable_section(ms))
 			return NOTIFY_BAD;
 	}
 	return NOTIFY_OK;