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  3. [PATCH 0/2] mm: Always use set_pXX() helpers to write page tables
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[PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables

Samuel Holland posted 2 patches 5 days, 8 hours ago
[PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables
Posted by Samuel Holland 5 days, 8 hours ago 
Generic code must always use the architecture-provided helper function
to write page tables.

Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers")
Fixes: c0fe07b0aa72 ("mm/debug_vm_pgtable: use struct pgtable_debug_args in PMD modifying tests")
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

 mm/debug_vm_pgtable.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index ae9b9310d96fd..8c7996d6c1f2a 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -445,7 +445,7 @@ static void __init pmd_huge_tests(struct pgtable_debug_args *args)
 	 * X86 defined pmd_set_huge() verifies that the given
 	 * PMD is not a populated non-leaf entry.
 	 */
-	WRITE_ONCE(*args->pmdp, __pmd(0));
+	set_pmd(args->pmdp, __pmd(0));
 	WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot));
 	WARN_ON(!pmd_clear_huge(args->pmdp));
 	pmd = pmdp_get(args->pmdp);
@@ -465,7 +465,7 @@ static void __init pud_huge_tests(struct pgtable_debug_args *args)
 	 * X86 defined pud_set_huge() verifies that the given
 	 * PUD is not a populated non-leaf entry.
 	 */
-	WRITE_ONCE(*args->pudp, __pud(0));
+	set_pud(args->pudp, __pud(0));
 	WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot));
 	WARN_ON(!pud_clear_huge(args->pudp));
 	pud = pudp_get(args->pudp);
-- 
2.47.2
Re: [PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables
Posted by kernel test robot 4 days, 4 hours ago 
Hi Samuel,

kernel test robot noticed the following build errors:

[auto build test ERROR on d358e5254674b70f34c847715ca509e46eb81e6f]

url:    https://github.com/intel-lab-lkp/linux/commits/Samuel-Holland/mm-debug_vm_pgtable-Use-set_pXd-to-write-page-tables/20251211-161254
base:   d358e5254674b70f34c847715ca509e46eb81e6f
patch link:    https://lore.kernel.org/r/20251211081117.1126521-2-samuel.holland%40sifive.com
patch subject: [PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables
config: powerpc64-randconfig-r064-20251212 (https://download.01.org/0day-ci/archive/20251212/202512121948.74kTIiJi-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 1335a05ab8bc8339ce24be3a9da89d8c3f4e0571)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251212/202512121948.74kTIiJi-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512121948.74kTIiJi-lkp@intel.com/

All errors (new ones prefixed by >>):

>> mm/debug_vm_pgtable.c:448:2: error: call to undeclared function 'set_pmd'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     448 |         set_pmd(args->pmdp, __pmd(0));
         |         ^
>> mm/debug_vm_pgtable.c:468:2: error: call to undeclared function 'set_pud'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     468 |         set_pud(args->pudp, __pud(0));
         |         ^
   2 errors generated.


vim +/set_pmd +448 mm/debug_vm_pgtable.c

   433	
   434	#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
   435	static void __init pmd_huge_tests(struct pgtable_debug_args *args)
   436	{
   437		pmd_t pmd;
   438	
   439		if (!arch_vmap_pmd_supported(args->page_prot) ||
   440		    args->fixed_alignment < PMD_SIZE)
   441			return;
   442	
   443		pr_debug("Validating PMD huge\n");
   444		/*
   445		 * X86 defined pmd_set_huge() verifies that the given
   446		 * PMD is not a populated non-leaf entry.
   447		 */
 > 448		set_pmd(args->pmdp, __pmd(0));
   449		WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot));
   450		WARN_ON(!pmd_clear_huge(args->pmdp));
   451		pmd = pmdp_get(args->pmdp);
   452		WARN_ON(!pmd_none(pmd));
   453	}
   454	
   455	static void __init pud_huge_tests(struct pgtable_debug_args *args)
   456	{
   457		pud_t pud;
   458	
   459		if (!arch_vmap_pud_supported(args->page_prot) ||
   460		    args->fixed_alignment < PUD_SIZE)
   461			return;
   462	
   463		pr_debug("Validating PUD huge\n");
   464		/*
   465		 * X86 defined pud_set_huge() verifies that the given
   466		 * PUD is not a populated non-leaf entry.
   467		 */
 > 468		set_pud(args->pudp, __pud(0));
   469		WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot));
   470		WARN_ON(!pud_clear_huge(args->pudp));
   471		pud = pudp_get(args->pudp);
   472		WARN_ON(!pud_none(pud));
   473	}
   474	#else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
   475	static void __init pmd_huge_tests(struct pgtable_debug_args *args) { }
   476	static void __init pud_huge_tests(struct pgtable_debug_args *args) { }
   477	#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
   478	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables
Posted by kernel test robot 4 days, 15 hours ago 
Hi Samuel,

kernel test robot noticed the following build errors:

[auto build test ERROR on d358e5254674b70f34c847715ca509e46eb81e6f]

url:    https://github.com/intel-lab-lkp/linux/commits/Samuel-Holland/mm-debug_vm_pgtable-Use-set_pXd-to-write-page-tables/20251211-161254
base:   d358e5254674b70f34c847715ca509e46eb81e6f
patch link:    https://lore.kernel.org/r/20251211081117.1126521-2-samuel.holland%40sifive.com
patch subject: [PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables
config: powerpc64-randconfig-r054-20251212 (https://download.01.org/0day-ci/archive/20251212/202512120808.akRJJMa7-lkp@intel.com/config)
compiler: powerpc64-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251212/202512120808.akRJJMa7-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512120808.akRJJMa7-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/debug_vm_pgtable.c: In function 'pmd_huge_tests':
>> mm/debug_vm_pgtable.c:448:2: error: implicit declaration of function 'set_pmd'; did you mean 'set_pgd'? [-Werror=implicit-function-declaration]
     448 |  set_pmd(args->pmdp, __pmd(0));
         |  ^~~~~~~
         |  set_pgd
   mm/debug_vm_pgtable.c: In function 'pud_huge_tests':
>> mm/debug_vm_pgtable.c:468:2: error: implicit declaration of function 'set_pud'; did you mean 'set_pgd'? [-Werror=implicit-function-declaration]
     468 |  set_pud(args->pudp, __pud(0));
         |  ^~~~~~~
         |  set_pgd
   cc1: some warnings being treated as errors

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for CAN_DEV
   Depends on [n]: NETDEVICES [=n] && CAN [=y]
   Selected by [y]:
   - CAN [=y] && NET [=y]


vim +448 mm/debug_vm_pgtable.c

   433	
   434	#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
   435	static void __init pmd_huge_tests(struct pgtable_debug_args *args)
   436	{
   437		pmd_t pmd;
   438	
   439		if (!arch_vmap_pmd_supported(args->page_prot) ||
   440		    args->fixed_alignment < PMD_SIZE)
   441			return;
   442	
   443		pr_debug("Validating PMD huge\n");
   444		/*
   445		 * X86 defined pmd_set_huge() verifies that the given
   446		 * PMD is not a populated non-leaf entry.
   447		 */
 > 448		set_pmd(args->pmdp, __pmd(0));
   449		WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot));
   450		WARN_ON(!pmd_clear_huge(args->pmdp));
   451		pmd = pmdp_get(args->pmdp);
   452		WARN_ON(!pmd_none(pmd));
   453	}
   454	
   455	static void __init pud_huge_tests(struct pgtable_debug_args *args)
   456	{
   457		pud_t pud;
   458	
   459		if (!arch_vmap_pud_supported(args->page_prot) ||
   460		    args->fixed_alignment < PUD_SIZE)
   461			return;
   462	
   463		pr_debug("Validating PUD huge\n");
   464		/*
   465		 * X86 defined pud_set_huge() verifies that the given
   466		 * PUD is not a populated non-leaf entry.
   467		 */
 > 468		set_pud(args->pudp, __pud(0));
   469		WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot));
   470		WARN_ON(!pud_clear_huge(args->pudp));
   471		pud = pudp_get(args->pudp);
   472		WARN_ON(!pud_none(pud));
   473	}
   474	#else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
   475	static void __init pmd_huge_tests(struct pgtable_debug_args *args) { }
   476	static void __init pud_huge_tests(struct pgtable_debug_args *args) { }
   477	#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
   478	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables
Posted by Ryan Roberts 5 days, 7 hours ago 
On 11/12/2025 08:11, Samuel Holland wrote:
> Generic code must always use the architecture-provided helper function
> to write page tables.
> 
> Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers")
> Fixes: c0fe07b0aa72 ("mm/debug_vm_pgtable: use struct pgtable_debug_args in PMD modifying tests")
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> ---
> 
>  mm/debug_vm_pgtable.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index ae9b9310d96fd..8c7996d6c1f2a 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -445,7 +445,7 @@ static void __init pmd_huge_tests(struct pgtable_debug_args *args)
>  	 * X86 defined pmd_set_huge() verifies that the given
>  	 * PMD is not a populated non-leaf entry.
>  	 */
> -	WRITE_ONCE(*args->pmdp, __pmd(0));
> +	set_pmd(args->pmdp, __pmd(0));

My guess is that this should actually be:

	pmd_clear(args->pmdp);

As the "clear" value may not be zero on some arches (see um) or there may be
more to do on other arches (see arm32's 2 level pgtable).

>  	WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot));
>  	WARN_ON(!pmd_clear_huge(args->pmdp));
>  	pmd = pmdp_get(args->pmdp);
> @@ -465,7 +465,7 @@ static void __init pud_huge_tests(struct pgtable_debug_args *args)
>  	 * X86 defined pud_set_huge() verifies that the given
>  	 * PUD is not a populated non-leaf entry.
>  	 */
> -	WRITE_ONCE(*args->pudp, __pud(0));
> +	set_pud(args->pudp, __pud(0));

Likewise, I think this should be:

	pud_clear(args->pudp);

Thanks,
Ryan

>  	WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot));
>  	WARN_ON(!pud_clear_huge(args->pudp));
>  	pud = pudp_get(args->pudp);
Re: [PATCH 1/2] mm/debug_vm_pgtable: Use set_pXd() to write page tables
Posted by Lorenzo Stoakes 1 day, 6 hours ago 
On Thu, Dec 11, 2025 at 09:36:27AM +0000, Ryan Roberts wrote:
> On 11/12/2025 08:11, Samuel Holland wrote:
> > Generic code must always use the architecture-provided helper function
> > to write page tables.
> >
> > Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers")
> > Fixes: c0fe07b0aa72 ("mm/debug_vm_pgtable: use struct pgtable_debug_args in PMD modifying tests")
> > Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> > ---
> >
> >  mm/debug_vm_pgtable.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> > index ae9b9310d96fd..8c7996d6c1f2a 100644
> > --- a/mm/debug_vm_pgtable.c
> > +++ b/mm/debug_vm_pgtable.c
> > @@ -445,7 +445,7 @@ static void __init pmd_huge_tests(struct pgtable_debug_args *args)
> >  	 * X86 defined pmd_set_huge() verifies that the given
> >  	 * PMD is not a populated non-leaf entry.
> >  	 */
> > -	WRITE_ONCE(*args->pmdp, __pmd(0));
> > +	set_pmd(args->pmdp, __pmd(0));
>
> My guess is that this should actually be:
>
> 	pmd_clear(args->pmdp);
>
> As the "clear" value may not be zero on some arches (see um) or there may be
> more to do on other arches (see arm32's 2 level pgtable).

Yeah, seems on looooongarch too for instance there's an invalid value being set
that is later checked by e.g. pmd_none().

>
> >  	WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot));
> >  	WARN_ON(!pmd_clear_huge(args->pmdp));
> >  	pmd = pmdp_get(args->pmdp);
> > @@ -465,7 +465,7 @@ static void __init pud_huge_tests(struct pgtable_debug_args *args)
> >  	 * X86 defined pud_set_huge() verifies that the given
> >  	 * PUD is not a populated non-leaf entry.
> >  	 */
> > -	WRITE_ONCE(*args->pudp, __pud(0));
> > +	set_pud(args->pudp, __pud(0));
>
> Likewise, I think this should be:
>
> 	pud_clear(args->pudp);
>
> Thanks,
> Ryan
>
> >  	WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot));
> >  	WARN_ON(!pud_clear_huge(args->pudp));
> >  	pud = pudp_get(args->pudp);
>

Yeah I'm with Ryan on this, also as the kernel build bot attests, it turns out
we don't even define set_pmd()/set_pud() for powerpc... :)

Patchew 2.1-devel-b67e4c2

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