Follow up of RFC patch:
https://lore.kernel.org/linux-mm/[email protected]/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/[email protected]/T/#m7d30b3afa632a4fa836f5fe55f4ee8e7bbc83e5d
https://lore.kernel.org/linux-mm/[email protected]/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
From: Sudarshan Rajagopalan <[email protected]>
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 <[email protected]>
Signed-off-by: Chris Goldsworthy <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Florian Fainelli <[email protected]>
Cc: Georgi Djakov <[email protected]>
---
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
On 9/28/2021 9:51 PM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Chris Goldsworthy <[email protected]>
> Acked-by: David Hildenbrand <[email protected]>
Tested-by: Georgi Djakov <[email protected]>
> Cc: Florian Fainelli <[email protected]>
> Cc: Georgi Djakov <[email protected]>
> ---
> 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;
> }
>
>
On Tue, 28 Sep 2021 11:51:48 -0700, Chris Goldsworthy wrote:
> Follow up of RFC patch:
>
> https://lore.kernel.org/linux-mm/[email protected]/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
On 9/29/21 12:21 AM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Chris Goldsworthy <[email protected]>
> Acked-by: David Hildenbrand <[email protected]>
> Cc: Florian Fainelli <[email protected]>
> Cc: Georgi Djakov <[email protected]>
> ---
> 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;
> }
>
>
On 01.10.21 08:38, Anshuman Khandual wrote:
>
>
> On 9/29/21 12:21 AM, Chris Goldsworthy wrote:
>> From: Sudarshan Rajagopalan <[email protected]>
>>
>> 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 <[email protected]>
>> Signed-off-by: Chris Goldsworthy <[email protected]>
>> Acked-by: David Hildenbrand <[email protected]>
>> Cc: Florian Fainelli <[email protected]>
>> Cc: Georgi Djakov <[email protected]>
>> ---
>> 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
On 9/29/21 12:21 AM, Chris Goldsworthy wrote:
> From: Sudarshan Rajagopalan <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Chris Goldsworthy <[email protected]>
> Acked-by: David Hildenbrand <[email protected]>
> Cc: Florian Fainelli <[email protected]>
> Cc: Georgi Djakov <[email protected]>
As these variables need to be updated in the platform.
Reviewed-by: Anshuman Khandual <[email protected]>
> ---
> 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;
> }
>
>