[PATCH V2] mm/ptdump: Drop GENERIC_PTDUMP

[PATCH V2] mm/ptdump: Drop GENERIC_PTDUMP

[Anshuman Khandual]

GENERIC_PTDUMP does not guard any code but instead just used for platform's
subscription into core ptdump defined under PTDUMP_CORE, which is selected.
Instead use PTDUMP_CORE for platform subscription and drop GENERIC_PTDUMP.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kvmarm@lists.linux.dev
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: linux-mm@kvack.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This patch applies on v6.14-rc1

Changes in V2:

- Keep arch/powerpc/Kconfig alphabetically sorted per Christophe

Changes in V1:

https://lore.kernel.org/all/20241217034807.2541349-1-anshuman.khandual@arm.com/

 Documentation/arch/arm64/ptdump.rst       | 1 -
 arch/arm64/Kconfig                        | 2 +-
 arch/arm64/kvm/Kconfig                    | 3 +--
 arch/powerpc/Kconfig                      | 2 +-
 arch/powerpc/configs/mpc885_ads_defconfig | 1 -
 arch/riscv/Kconfig                        | 2 +-
 arch/s390/Kconfig                         | 2 +-
 arch/x86/Kconfig                          | 2 +-
 arch/x86/Kconfig.debug                    | 2 +-
 kernel/configs/debug.config               | 1 -
 mm/Kconfig.debug                          | 8 ++------
 11 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/Documentation/arch/arm64/ptdump.rst b/Documentation/arch/arm64/ptdump.rst
index 5dcfc5d7cddf..61ca040a885b 100644
--- a/Documentation/arch/arm64/ptdump.rst
+++ b/Documentation/arch/arm64/ptdump.rst
@@ -22,7 +22,6 @@ offlining of memory being accessed by the ptdump code.
 In order to dump the kernel page tables, enable the following
 configurations and mount debugfs::
 
- CONFIG_GENERIC_PTDUMP=y
  CONFIG_PTDUMP_CORE=y
  CONFIG_PTDUMP_DEBUGFS=y
 
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fcdd0ed3eca8..1f516bed81dd 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -157,7 +157,7 @@ config ARM64
 	select GENERIC_IRQ_SHOW_LEVEL
 	select GENERIC_LIB_DEVMEM_IS_ALLOWED
 	select GENERIC_PCI_IOMAP
-	select GENERIC_PTDUMP
+	select PTDUMP_CORE
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index ead632ad01b4..fe17d7f5b061 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -71,8 +71,7 @@ config PTDUMP_STAGE2_DEBUGFS
 	depends on KVM
 	depends on DEBUG_KERNEL
 	depends on DEBUG_FS
-	depends on GENERIC_PTDUMP
-	select PTDUMP_CORE
+	depends on PTDUMP_CORE
 	default n
 	help
 	  Say Y here if you want to show the stage-2 kernel pagetables
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 424f188e62d9..97312440f715 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -206,7 +206,6 @@ config PPC
 	select GENERIC_IRQ_SHOW
 	select GENERIC_IRQ_SHOW_LEVEL
 	select GENERIC_PCI_IOMAP		if PCI
-	select GENERIC_PTDUMP
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
 	select GENERIC_VDSO_TIME_NS
@@ -314,6 +313,7 @@ config PPC
 	select PCI_MSI_ARCH_FALLBACKS		if PCI_MSI
 	select PCI_SYSCALL			if PCI
 	select PPC_DAWR				if PPC64
+	select PTDUMP_CORE
 	select RTC_LIB
 	select SPARSE_IRQ
 	select STRICT_KERNEL_RWX if STRICT_MODULE_RWX
diff --git a/arch/powerpc/configs/mpc885_ads_defconfig b/arch/powerpc/configs/mpc885_ads_defconfig
index 77306be62e9e..ea6f836407d2 100644
--- a/arch/powerpc/configs/mpc885_ads_defconfig
+++ b/arch/powerpc/configs/mpc885_ads_defconfig
@@ -78,4 +78,3 @@ CONFIG_DEBUG_VM_PGTABLE=y
 CONFIG_DETECT_HUNG_TASK=y
 CONFIG_BDI_SWITCH=y
 CONFIG_PPC_EARLY_DEBUG=y
-CONFIG_GENERIC_PTDUMP=y
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 7612c52e9b1e..bdaf08c1e1da 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -112,7 +112,7 @@ config RISCV
 	select GENERIC_IRQ_SHOW_LEVEL
 	select GENERIC_LIB_DEVMEM_IS_ALLOWED
 	select GENERIC_PCI_IOMAP
-	select GENERIC_PTDUMP if MMU
+	select PTDUMP_CORE if MMU
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL if MMU && 64BIT
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9c9ec08d78c7..ecf6b4cb3e33 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -163,7 +163,7 @@ config S390
 	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_ENTRY
 	select GENERIC_GETTIMEOFDAY
-	select GENERIC_PTDUMP
+	select PTDUMP_CORE
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
 	select GENERIC_VDSO_TIME_NS
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 87198d957e2f..b6097b6178de 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -174,7 +174,7 @@ config X86
 	select GENERIC_IRQ_RESERVATION_MODE
 	select GENERIC_IRQ_SHOW
 	select GENERIC_PENDING_IRQ		if SMP
-	select GENERIC_PTDUMP
+	select PTDUMP_CORE
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_TIME_VSYSCALL
 	select GENERIC_GETTIMEOFDAY
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 1eb4d23cdaae..090c44d7e1a5 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -59,7 +59,7 @@ config EARLY_PRINTK_USB_XDBC
 config EFI_PGT_DUMP
 	bool "Dump the EFI pagetable"
 	depends on EFI
-	select PTDUMP_CORE
+	depends on PTDUMP_CORE
 	help
 	  Enable this if you want to dump the EFI page table before
 	  enabling virtual mode. This can be used to debug miscellaneous
diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config
index 20552f163930..8aafd050b754 100644
--- a/kernel/configs/debug.config
+++ b/kernel/configs/debug.config
@@ -73,7 +73,6 @@ CONFIG_DEBUG_VM=y
 CONFIG_DEBUG_VM_PGFLAGS=y
 CONFIG_DEBUG_VM_RB=y
 CONFIG_DEBUG_VM_VMACACHE=y
-CONFIG_GENERIC_PTDUMP=y
 CONFIG_KASAN=y
 CONFIG_KASAN_GENERIC=y
 CONFIG_KASAN_INLINE=y
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 41a58536531d..b206e5a11f96 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -187,7 +187,7 @@ config DEBUG_WX
 	bool "Warn on W+X mappings at boot"
 	depends on ARCH_HAS_DEBUG_WX
 	depends on MMU
-	select PTDUMP_CORE
+	depends on PTDUMP_CORE
 	help
 	  Generate a warning if any W+X mappings are found at boot.
 
@@ -212,9 +212,6 @@ config DEBUG_WX
 
 	  If in doubt, say "Y".
 
-config GENERIC_PTDUMP
-	bool
-
 config PTDUMP_CORE
 	bool
 
@@ -222,8 +219,7 @@ config PTDUMP_DEBUGFS
 	bool "Export kernel pagetable layout to userspace via debugfs"
 	depends on DEBUG_KERNEL
 	depends on DEBUG_FS
-	depends on GENERIC_PTDUMP
-	select PTDUMP_CORE
+	depends on PTDUMP_CORE
 	help
 	  Say Y here if you want to show the kernel pagetable layout in a
 	  debugfs file. This information is only useful for kernel developers
-- 
2.30.2

Re: [PATCH V2] mm/ptdump: Drop GENERIC_PTDUMP

[Mark Rutland]

On Wed, Feb 05, 2025 at 10:30:39AM +0530, Anshuman Khandual wrote:
> GENERIC_PTDUMP does not guard any code but instead just used for platform's
> subscription into core ptdump defined under PTDUMP_CORE, which is selected.

Selected by what?

> Instead use PTDUMP_CORE for platform subscription and drop GENERIC_PTDUMP.
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Paul Walmsley <paul.walmsley@sifive.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Heiko Carstens <hca@linux.ibm.com>
> Cc: Vasily Gorbik <gor@linux.ibm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kvmarm@lists.linux.dev
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-riscv@lists.infradead.org
> Cc: linux-s390@vger.kernel.org
> Cc: linux-mm@kvack.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> This patch applies on v6.14-rc1
> 
> Changes in V2:
> 
> - Keep arch/powerpc/Kconfig alphabetically sorted per Christophe
> 
> Changes in V1:
> 
> https://lore.kernel.org/all/20241217034807.2541349-1-anshuman.khandual@arm.com/
> 
>  Documentation/arch/arm64/ptdump.rst       | 1 -
>  arch/arm64/Kconfig                        | 2 +-
>  arch/arm64/kvm/Kconfig                    | 3 +--
>  arch/powerpc/Kconfig                      | 2 +-
>  arch/powerpc/configs/mpc885_ads_defconfig | 1 -
>  arch/riscv/Kconfig                        | 2 +-
>  arch/s390/Kconfig                         | 2 +-
>  arch/x86/Kconfig                          | 2 +-
>  arch/x86/Kconfig.debug                    | 2 +-
>  kernel/configs/debug.config               | 1 -
>  mm/Kconfig.debug                          | 8 ++------
>  11 files changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/Documentation/arch/arm64/ptdump.rst b/Documentation/arch/arm64/ptdump.rst
> index 5dcfc5d7cddf..61ca040a885b 100644
> --- a/Documentation/arch/arm64/ptdump.rst
> +++ b/Documentation/arch/arm64/ptdump.rst
> @@ -22,7 +22,6 @@ offlining of memory being accessed by the ptdump code.
>  In order to dump the kernel page tables, enable the following
>  configurations and mount debugfs::
>  
> - CONFIG_GENERIC_PTDUMP=y
>   CONFIG_PTDUMP_CORE=y
>   CONFIG_PTDUMP_DEBUGFS=y
>  
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index fcdd0ed3eca8..1f516bed81dd 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -157,7 +157,7 @@ config ARM64
>  	select GENERIC_IRQ_SHOW_LEVEL
>  	select GENERIC_LIB_DEVMEM_IS_ALLOWED
>  	select GENERIC_PCI_IOMAP
> -	select GENERIC_PTDUMP
> +	select PTDUMP_CORE
>  	select GENERIC_SCHED_CLOCK
>  	select GENERIC_SMP_IDLE_THREAD
>  	select GENERIC_TIME_VSYSCALL

This change means that the ptdump core code will be built regardless of
whether any users are selected:

  [mark@lakrids:~/src/linux]% git grep CONFIG_PTDUMP_CORE
  Documentation/arch/arm64/ptdump.rst: CONFIG_PTDUMP_CORE=y
  arch/arm64/include/asm/ptdump.h:#ifdef CONFIG_PTDUMP_CORE
  arch/arm64/include/asm/ptdump.h:#endif /* CONFIG_PTDUMP_CORE */
  arch/arm64/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE)        += ptdump.o
  arch/powerpc/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE)      += ptdump/
  arch/riscv/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
  arch/s390/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += dump_pagetables.o
  arch/x86/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE)  += dump_pagetables.o
  mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump.o

GENERIC_PTDUMP means "this architecture uses generic ptdump code for
ptdump", i.e. the architecture implements all the necessary bits for
that to work *IF* it is built.

PTDUMP_CORE means "actually build the core ptdump code".

If everyone uses the generic ptdump code now, maybe it's worth renaming
GENERIC_PTDUMP to ARCH_HAS_PTDUMP or something like that, but I don't
think this change makes sense as-is.

[...]

> diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config
> index 20552f163930..8aafd050b754 100644
> --- a/kernel/configs/debug.config
> +++ b/kernel/configs/debug.config
> @@ -73,7 +73,6 @@ CONFIG_DEBUG_VM=y
>  CONFIG_DEBUG_VM_PGFLAGS=y
>  CONFIG_DEBUG_VM_RB=y
>  CONFIG_DEBUG_VM_VMACACHE=y
> -CONFIG_GENERIC_PTDUMP=y
>  CONFIG_KASAN=y
>  CONFIG_KASAN_GENERIC=y
>  CONFIG_KASAN_INLINE=y

I think this is wrong today, and removing it is the right thing to do.

Architectures with support will select this themselves, and on
architectures without support this either does nothing or causes a build
failure.

Mark.

Re: [PATCH V2] mm/ptdump: Drop GENERIC_PTDUMP

[Anshuman Khandual]

On 2/5/25 15:31, Mark Rutland wrote:
> On Wed, Feb 05, 2025 at 10:30:39AM +0530, Anshuman Khandual wrote:
>> GENERIC_PTDUMP does not guard any code but instead just used for platform's
>> subscription into core ptdump defined under PTDUMP_CORE, which is selected.
> 
> Selected by what?

I guess that sentence was incomplete. PTDUMP_CORE gets selected by all
the real users which requires core PTDUMP to be built and enabled.

arch/arm64/kvm/Kconfig: select PTDUMP_CORE	/* config PTDUMP_STAGE2_DEBUGFS */
arch/x86/Kconfig.debug: select PTDUMP_CORE	/* config EFI_PGT_DUMP */

mm/Kconfig.debug:       select PTDUMP_CORE	/* config PTDUMP_DEBUGFS */
mm/Kconfig.debug:       select PTDUMP_CORE	/* config DEBUG_WX */

> 
>> Instead use PTDUMP_CORE for platform subscription and drop GENERIC_PTDUMP.
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Jonathan Corbet <corbet@lwn.net>
>> Cc: Marc Zyngier <maz@kernel.org>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: Nicholas Piggin <npiggin@gmail.com>
>> Cc: Paul Walmsley <paul.walmsley@sifive.com>
>> Cc: Palmer Dabbelt <palmer@dabbelt.com>
>> Cc: Heiko Carstens <hca@linux.ibm.com>
>> Cc: Vasily Gorbik <gor@linux.ibm.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: linux-doc@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Cc: kvmarm@lists.linux.dev
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Cc: linux-riscv@lists.infradead.org
>> Cc: linux-s390@vger.kernel.org
>> Cc: linux-mm@kvack.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>> This patch applies on v6.14-rc1
>>
>> Changes in V2:
>>
>> - Keep arch/powerpc/Kconfig alphabetically sorted per Christophe
>>
>> Changes in V1:
>>
>> https://lore.kernel.org/all/20241217034807.2541349-1-anshuman.khandual@arm.com/
>>
>>  Documentation/arch/arm64/ptdump.rst       | 1 -
>>  arch/arm64/Kconfig                        | 2 +-
>>  arch/arm64/kvm/Kconfig                    | 3 +--
>>  arch/powerpc/Kconfig                      | 2 +-
>>  arch/powerpc/configs/mpc885_ads_defconfig | 1 -
>>  arch/riscv/Kconfig                        | 2 +-
>>  arch/s390/Kconfig                         | 2 +-
>>  arch/x86/Kconfig                          | 2 +-
>>  arch/x86/Kconfig.debug                    | 2 +-
>>  kernel/configs/debug.config               | 1 -
>>  mm/Kconfig.debug                          | 8 ++------
>>  11 files changed, 9 insertions(+), 17 deletions(-)
>>
>> diff --git a/Documentation/arch/arm64/ptdump.rst b/Documentation/arch/arm64/ptdump.rst
>> index 5dcfc5d7cddf..61ca040a885b 100644
>> --- a/Documentation/arch/arm64/ptdump.rst
>> +++ b/Documentation/arch/arm64/ptdump.rst
>> @@ -22,7 +22,6 @@ offlining of memory being accessed by the ptdump code.
>>  In order to dump the kernel page tables, enable the following
>>  configurations and mount debugfs::
>>  
>> - CONFIG_GENERIC_PTDUMP=y
>>   CONFIG_PTDUMP_CORE=y
>>   CONFIG_PTDUMP_DEBUGFS=y
>>  
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index fcdd0ed3eca8..1f516bed81dd 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -157,7 +157,7 @@ config ARM64
>>  	select GENERIC_IRQ_SHOW_LEVEL
>>  	select GENERIC_LIB_DEVMEM_IS_ALLOWED
>>  	select GENERIC_PCI_IOMAP
>> -	select GENERIC_PTDUMP
>> +	select PTDUMP_CORE
>>  	select GENERIC_SCHED_CLOCK
>>  	select GENERIC_SMP_IDLE_THREAD
>>  	select GENERIC_TIME_VSYSCALL
> 
> This change means that the ptdump core code will be built regardless of
> whether any users are selected:
> 
>   [mark@lakrids:~/src/linux]% git grep CONFIG_PTDUMP_CORE
>   Documentation/arch/arm64/ptdump.rst: CONFIG_PTDUMP_CORE=y
>   arch/arm64/include/asm/ptdump.h:#ifdef CONFIG_PTDUMP_CORE
>   arch/arm64/include/asm/ptdump.h:#endif /* CONFIG_PTDUMP_CORE */
>   arch/arm64/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE)        += ptdump.o
>   arch/powerpc/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE)      += ptdump/
>   arch/riscv/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
>   arch/s390/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += dump_pagetables.o
>   arch/x86/mm/Makefile:obj-$(CONFIG_PTDUMP_CORE)  += dump_pagetables.o
>   mm/Makefile:obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
> 
> GENERIC_PTDUMP means "this architecture uses generic ptdump code for
> ptdump", i.e. the architecture implements all the necessary bits for
> that to work *IF* it is built.
> 
> PTDUMP_CORE means "actually build the core ptdump code".
> 
> If everyone uses the generic ptdump code now, maybe it's worth renaming
> GENERIC_PTDUMP to ARCH_HAS_PTDUMP or something like that, but I don't
> think this change makes sense as-is.

Seems like a combination of ARCH_HAS_CORE_PTDUMP for subscription and
CORE_PTDUMP for actual enablement will make things clear. _CORE_ here
would still let platforms define their own CONFIG_PTDUMP if preferred
and not subscribe the generic CORE_DUMP.

currently GENERIC_PTDUMP and CORE_PTDUMP just seems disjoint, because
GENERIC_PTDUMP does not not appear to be the platform opt in required
for CORE_PTDUMP.

There is another problem.

mm/Kconfig.debug

config DEBUG_WX
        bool "Warn on W+X mappings at boot"
        depends on ARCH_HAS_DEBUG_WX
        depends on MMU
        select PTDUMP_CORE
        help

Before selecting PTDUMP_CORE it does not ensure platform has opted in
via GENERIC_PTDUMP or not. Instead it should be

config DEBUG_WX
        bool "Warn on W+X mappings at boot"
        depends on ARCH_HAS_DEBUG_WX
	depends on GENERIC_PTDUMP
	depends on 
        depends on MMU
        select PTDUMP_CORE
        help

PTDUMP_STAGE2_DEBUGFS on arm64 does that where as EFI_PGT_DUMP on x86
does not. Although it will be ideal but that's not a problem if the
platform knows for sure that it opts in GENERIC_PTDUMP.

> 
> [...]
> 
>> diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config
>> index 20552f163930..8aafd050b754 100644
>> --- a/kernel/configs/debug.config
>> +++ b/kernel/configs/debug.config
>> @@ -73,7 +73,6 @@ CONFIG_DEBUG_VM=y
>>  CONFIG_DEBUG_VM_PGFLAGS=y
>>  CONFIG_DEBUG_VM_RB=y
>>  CONFIG_DEBUG_VM_VMACACHE=y
>> -CONFIG_GENERIC_PTDUMP=y
>>  CONFIG_KASAN=y
>>  CONFIG_KASAN_GENERIC=y
>>  CONFIG_KASAN_INLINE=y
> 
> I think this is wrong today, and removing it is the right thing to do.
> 
> Architectures with support will select this themselves, and on
> architectures without support this either does nothing or causes a build
> failure.

Alright, will separate this change out first.