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* arm64: mm: update max_pfn after memory hotplug
@ 2021-09-28 18:51 Chris Goldsworthy
  2021-09-28 18:51 ` [PATCH] " Chris Goldsworthy
  2021-09-29 17:48 ` Will Deacon
  0 siblings, 2 replies; 7+ messages in thread
From: Chris Goldsworthy @ 2021-09-28 18:51 UTC (permalink / raw)
  To: Andrew Morton
  Cc: David Hildenbrand, Catalin Marinas, Will Deacon,
	Sudarshan Rajagopalan, Georgi Djakov, linux-arm-kernel,
	linux-kernel, linux-mm, Chris Goldsworthy

Follow up of RFC patch:

https://lore.kernel.org/linux-mm/a3bf84c4-8f35-f273-145c-55928a06f332@quicinc.com/T/#m219937b1acdd40318bbe90ab39f187804775eb74

On arm64 we set max_pfn at boot in arch/arm64/mm/init.c. If you
hotplug in memory after booting up, max_pfn is not updated. This
breaks diagnostic functions executed from user space like
read_page_owner():

https://elixir.bootlin.com/linux/v5.14.7/source/mm/page_owner.c#L472

or kpageflags_read() (see how get_max_dump_pfn() is used):

https://elixir.bootlin.com/linux/v5.14.7/source/fs/proc/page.c#L47

Thus, this patch updates max_pfn and max_low_pfn in arm64's
arch_add_memory() function, mirroring what is updatated during boot:

https://elixir.bootlin.com/linux/v5.14.7/source/arch/arm64/mm/init.c#L448

Quick reference for David's Acked-by, with a follow-up discussion on
max_low_pfn:

https://lore.kernel.org/linux-mm/a3bf84c4-8f35-f273-145c-55928a06f332@quicinc.com/T/#m7d30b3afa632a4fa836f5fe55f4ee8e7bbc83e5d
https://lore.kernel.org/linux-mm/a3bf84c4-8f35-f273-145c-55928a06f332@quicinc.com/T/#m0d0e509375af1504d25451d079c5cbd6e7aa513b

Sudarshan Rajagopalan (1):
  arm64: mm: update max_pfn after memory hotplug

 arch/arm64/mm/mmu.c | 5 +++++
 1 file changed, 5 insertions(+)

-- 
2.7.4


^ permalink raw reply	[flat|nested] 7+ messages in thread

* [PATCH] arm64: mm: update max_pfn after memory hotplug
  2021-09-28 18:51 arm64: mm: update max_pfn after memory hotplug Chris Goldsworthy
@ 2021-09-28 18:51 ` Chris Goldsworthy
  2021-09-28 19:34   ` Georgi Djakov
                     ` (2 more replies)
  2021-09-29 17:48 ` Will Deacon
  1 sibling, 3 replies; 7+ messages in thread
From: Chris Goldsworthy @ 2021-09-28 18:51 UTC (permalink / raw)
  To: Andrew Morton
  Cc: David Hildenbrand, Catalin Marinas, Will Deacon,
	Sudarshan Rajagopalan, Georgi Djakov, linux-arm-kernel,
	linux-kernel, linux-mm, Chris Goldsworthy, Florian Fainelli

From: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>

After new memory blocks have been hotplugged, max_pfn and max_low_pfn
needs updating to reflect on new PFNs being hot added to system.
Without this patch, debug-related functions that use max_pfn such as
get_max_dump_pfn() or read_page_owner() will not work with any page in
memory that is hot-added after boot. 

Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
Signed-off-by: Chris Goldsworthy <quic_cgoldswo@quicinc.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Georgi Djakov <quic_c_gdjako@quicinc.com>
---
 arch/arm64/mm/mmu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index cfd9deb..fd85b51 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
 	if (ret)
 		__remove_pgd_mapping(swapper_pg_dir,
 				     __phys_to_virt(start), size);
+	else {
+		max_pfn = PFN_UP(start + size);
+		max_low_pfn = max_pfn;
+	}
+
 	return ret;
 }
 
-- 
2.7.4


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] arm64: mm: update max_pfn after memory hotplug
  2021-09-28 18:51 ` [PATCH] " Chris Goldsworthy
@ 2021-09-28 19:34   ` Georgi Djakov
  2021-10-01  6:38   ` Anshuman Khandual
  2021-10-01  8:52   ` Anshuman Khandual
  2 siblings, 0 replies; 7+ messages in thread
From: Georgi Djakov @ 2021-09-28 19:34 UTC (permalink / raw)
  To: Chris Goldsworthy, Andrew Morton
  Cc: David Hildenbrand, Catalin Marinas, Will Deacon,
	Sudarshan Rajagopalan, linux-arm-kernel, linux-kernel, linux-mm,
	Florian Fainelli

On 9/28/2021 9:51 PM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
> 
> After new memory blocks have been hotplugged, max_pfn and max_low_pfn
> needs updating to reflect on new PFNs being hot added to system.
> Without this patch, debug-related functions that use max_pfn such as
> get_max_dump_pfn() or read_page_owner() will not work with any page in
> memory that is hot-added after boot.
> 
> Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
> Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
> Signed-off-by: Chris Goldsworthy <quic_cgoldswo@quicinc.com>
> Acked-by: David Hildenbrand <david@redhat.com>

Tested-by: Georgi Djakov <quic_c_gdjako@quicinc.com>

> Cc: Florian Fainelli <f.fainelli@gmail.com>
> Cc: Georgi Djakov <quic_c_gdjako@quicinc.com>
> ---
>   arch/arm64/mm/mmu.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index cfd9deb..fd85b51 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
>   	if (ret)
>   		__remove_pgd_mapping(swapper_pg_dir,
>   				     __phys_to_virt(start), size);
> +	else {
> +		max_pfn = PFN_UP(start + size);
> +		max_low_pfn = max_pfn;
> +	}
> +
>   	return ret;
>   }
>   
> 

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: arm64: mm: update max_pfn after memory hotplug
  2021-09-28 18:51 arm64: mm: update max_pfn after memory hotplug Chris Goldsworthy
  2021-09-28 18:51 ` [PATCH] " Chris Goldsworthy
@ 2021-09-29 17:48 ` Will Deacon
  1 sibling, 0 replies; 7+ messages in thread
From: Will Deacon @ 2021-09-29 17:48 UTC (permalink / raw)
  To: Chris Goldsworthy, Andrew Morton
  Cc: catalin.marinas, kernel-team, Will Deacon, linux-kernel,
	linux-arm-kernel, linux-mm, Georgi Djakov, Sudarshan Rajagopalan,
	David Hildenbrand

On Tue, 28 Sep 2021 11:51:48 -0700, Chris Goldsworthy wrote:
> Follow up of RFC patch:
> 
> https://lore.kernel.org/linux-mm/a3bf84c4-8f35-f273-145c-55928a06f332@quicinc.com/T/#m219937b1acdd40318bbe90ab39f187804775eb74
> 
> On arm64 we set max_pfn at boot in arch/arm64/mm/init.c. If you
> hotplug in memory after booting up, max_pfn is not updated. This
> breaks diagnostic functions executed from user space like
> read_page_owner():
> 
> [...]

Applied to arm64 (for-next/mm), thanks!

[1/1] arm64: mm: update max_pfn after memory hotplug
      https://git.kernel.org/arm64/c/8fac67ca236b

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] arm64: mm: update max_pfn after memory hotplug
  2021-09-28 18:51 ` [PATCH] " Chris Goldsworthy
  2021-09-28 19:34   ` Georgi Djakov
@ 2021-10-01  6:38   ` Anshuman Khandual
  2021-10-01  8:39     ` David Hildenbrand
  2021-10-01  8:52   ` Anshuman Khandual
  2 siblings, 1 reply; 7+ messages in thread
From: Anshuman Khandual @ 2021-10-01  6:38 UTC (permalink / raw)
  To: Chris Goldsworthy, Andrew Morton
  Cc: David Hildenbrand, Catalin Marinas, Will Deacon,
	Sudarshan Rajagopalan, Georgi Djakov, linux-arm-kernel,
	linux-kernel, linux-mm, Florian Fainelli



On 9/29/21 12:21 AM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
> 
> After new memory blocks have been hotplugged, max_pfn and max_low_pfn
> needs updating to reflect on new PFNs being hot added to system.
> Without this patch, debug-related functions that use max_pfn such as
> get_max_dump_pfn() or read_page_owner() will not work with any page in
> memory that is hot-added after boot. 
> 
> Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
> Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
> Signed-off-by: Chris Goldsworthy <quic_cgoldswo@quicinc.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> Cc: Florian Fainelli <f.fainelli@gmail.com>
> Cc: Georgi Djakov <quic_c_gdjako@quicinc.com>
> ---
>  arch/arm64/mm/mmu.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index cfd9deb..fd85b51 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
>  	if (ret)
>  		__remove_pgd_mapping(swapper_pg_dir,
>  				     __phys_to_virt(start), size);
> +	else {
> +		max_pfn = PFN_UP(start + size);
> +		max_low_pfn = max_pfn;
> +	}

Do these variables get updated on *all* platforms that support memory
hotplug via an arch_add_memory() ? If not, dont they all face similar
issues as well ? Why not just update these in generic hotplug instead
, after looking into arch_add_memory() return code.

> +
>  	return ret;
>  }
>  
> 

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] arm64: mm: update max_pfn after memory hotplug
  2021-10-01  6:38   ` Anshuman Khandual
@ 2021-10-01  8:39     ` David Hildenbrand
  0 siblings, 0 replies; 7+ messages in thread
From: David Hildenbrand @ 2021-10-01  8:39 UTC (permalink / raw)
  To: Anshuman Khandual, Chris Goldsworthy, Andrew Morton
  Cc: Catalin Marinas, Will Deacon, Sudarshan Rajagopalan,
	Georgi Djakov, linux-arm-kernel, linux-kernel, linux-mm,
	Florian Fainelli

On 01.10.21 08:38, Anshuman Khandual wrote:
> 
> 
> On 9/29/21 12:21 AM, Chris Goldsworthy wrote:
>> From: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
>>
>> After new memory blocks have been hotplugged, max_pfn and max_low_pfn
>> needs updating to reflect on new PFNs being hot added to system.
>> Without this patch, debug-related functions that use max_pfn such as
>> get_max_dump_pfn() or read_page_owner() will not work with any page in
>> memory that is hot-added after boot.
>>
>> Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
>> Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
>> Signed-off-by: Chris Goldsworthy <quic_cgoldswo@quicinc.com>
>> Acked-by: David Hildenbrand <david@redhat.com>
>> Cc: Florian Fainelli <f.fainelli@gmail.com>
>> Cc: Georgi Djakov <quic_c_gdjako@quicinc.com>
>> ---
>>   arch/arm64/mm/mmu.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index cfd9deb..fd85b51 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
>>   	if (ret)
>>   		__remove_pgd_mapping(swapper_pg_dir,
>>   				     __phys_to_virt(start), size);
>> +	else {
>> +		max_pfn = PFN_UP(start + size);
>> +		max_low_pfn = max_pfn;
>> +	}
> 
> Do these variables get updated on *all* platforms that support memory
> hotplug via an arch_add_memory() ? If not, dont they all face similar
> issues as well ? Why not just update these in generic hotplug instead
> , after looking into arch_add_memory() return code.

s390x sets them to the possible maximum (based on the direct mapping 
size) in init code.

Other archs like x86-64 have to update other parameters. So I guess it 
just made sense to let the archs handle updating these 2 variables.

-- 
Thanks,

David / dhildenb


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH] arm64: mm: update max_pfn after memory hotplug
  2021-09-28 18:51 ` [PATCH] " Chris Goldsworthy
  2021-09-28 19:34   ` Georgi Djakov
  2021-10-01  6:38   ` Anshuman Khandual
@ 2021-10-01  8:52   ` Anshuman Khandual
  2 siblings, 0 replies; 7+ messages in thread
From: Anshuman Khandual @ 2021-10-01  8:52 UTC (permalink / raw)
  To: Chris Goldsworthy, Andrew Morton
  Cc: David Hildenbrand, Catalin Marinas, Will Deacon,
	Sudarshan Rajagopalan, Georgi Djakov, linux-arm-kernel,
	linux-kernel, linux-mm, Florian Fainelli



On 9/29/21 12:21 AM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
> 
> After new memory blocks have been hotplugged, max_pfn and max_low_pfn
> needs updating to reflect on new PFNs being hot added to system.
> Without this patch, debug-related functions that use max_pfn such as
> get_max_dump_pfn() or read_page_owner() will not work with any page in
> memory that is hot-added after boot. 
> 
> Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
> Signed-off-by: Sudarshan Rajagopalan <quic_sudaraja@quicinc.com>
> Signed-off-by: Chris Goldsworthy <quic_cgoldswo@quicinc.com>
> Acked-by: David Hildenbrand <david@redhat.com>
> Cc: Florian Fainelli <f.fainelli@gmail.com>
> Cc: Georgi Djakov <quic_c_gdjako@quicinc.com>

As these variables need to be updated in the platform.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

> ---
>  arch/arm64/mm/mmu.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index cfd9deb..fd85b51 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1499,6 +1499,11 @@ int arch_add_memory(int nid, u64 start, u64 size,
>  	if (ret)
>  		__remove_pgd_mapping(swapper_pg_dir,
>  				     __phys_to_virt(start), size);
> +	else {
> +		max_pfn = PFN_UP(start + size);
> +		max_low_pfn = max_pfn;
> +	}
> +
>  	return ret;
>  }
>  
> 

^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2021-10-01  8:51 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-09-28 18:51 arm64: mm: update max_pfn after memory hotplug Chris Goldsworthy
2021-09-28 18:51 ` [PATCH] " Chris Goldsworthy
2021-09-28 19:34   ` Georgi Djakov
2021-10-01  6:38   ` Anshuman Khandual
2021-10-01  8:39     ` David Hildenbrand
2021-10-01  8:52   ` Anshuman Khandual
2021-09-29 17:48 ` Will Deacon

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