Re: [PATCH v3 4/4] arch, mm: make kernel_page_present() always available

[David Hildenbrand <david@redhat.com>]

On 01.11.20 18:08, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.ibm.com>
> 
> For architectures that enable ARCH_HAS_SET_MEMORY having the ability to
> verify that a page is mapped in the kernel direct map can be useful
> regardless of hibernation.
> 
> Add RISC-V implementation of kernel_page_present(), update its forward
> declarations and stubs to be a part of set_memory API and remove ugly
> ifdefery in inlcude/linux/mm.h around current declarations of
> kernel_page_present().
> 
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
>   arch/arm64/include/asm/cacheflush.h |  1 +
>   arch/arm64/mm/pageattr.c            |  4 +---
>   arch/riscv/include/asm/set_memory.h |  1 +
>   arch/riscv/mm/pageattr.c            | 29 +++++++++++++++++++++++++++++
>   arch/x86/include/asm/set_memory.h   |  1 +
>   arch/x86/mm/pat/set_memory.c        |  4 +---
>   include/linux/mm.h                  |  7 -------
>   include/linux/set_memory.h          |  5 +++++
>   8 files changed, 39 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
> index 9384fd8fc13c..45217f21f1fe 100644
> --- a/arch/arm64/include/asm/cacheflush.h
> +++ b/arch/arm64/include/asm/cacheflush.h
> @@ -140,6 +140,7 @@ int set_memory_valid(unsigned long addr, int numpages, int enable);
>   
>   int set_direct_map_invalid_noflush(struct page *page);
>   int set_direct_map_default_noflush(struct page *page);
> +bool kernel_page_present(struct page *page);
>   
>   #include <asm-generic/cacheflush.h>
>   
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 439325532be1..92eccaf595c8 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -186,8 +186,8 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
>   
>   	set_memory_valid((unsigned long)page_address(page), numpages, enable);
>   }
> +#endif /* CONFIG_DEBUG_PAGEALLOC */
>   
> -#ifdef CONFIG_HIBERNATION
>   /*
>    * This function is used to determine if a linear map page has been marked as
>    * not-valid. Walk the page table and check the PTE_VALID bit. This is based
> @@ -234,5 +234,3 @@ bool kernel_page_present(struct page *page)
>   	ptep = pte_offset_kernel(pmdp, addr);
>   	return pte_valid(READ_ONCE(*ptep));
>   }
> -#endif /* CONFIG_HIBERNATION */
> -#endif /* CONFIG_DEBUG_PAGEALLOC */
> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
> index 4c5bae7ca01c..d690b08dff2a 100644
> --- a/arch/riscv/include/asm/set_memory.h
> +++ b/arch/riscv/include/asm/set_memory.h
> @@ -24,6 +24,7 @@ static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
>   
>   int set_direct_map_invalid_noflush(struct page *page);
>   int set_direct_map_default_noflush(struct page *page);
> +bool kernel_page_present(struct page *page);
>   
>   #endif /* __ASSEMBLY__ */
>   
> diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
> index 321b09d2e2ea..87ba5a68bbb8 100644
> --- a/arch/riscv/mm/pageattr.c
> +++ b/arch/riscv/mm/pageattr.c
> @@ -198,3 +198,32 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
>   			     __pgprot(0), __pgprot(_PAGE_PRESENT));
>   }
>   #endif
> +
> +bool kernel_page_present(struct page *page)
> +{
> +	unsigned long addr = (unsigned long)page_address(page);
> +	pgd_t *pgd;
> +	pud_t *pud;
> +	p4d_t *p4d;
> +	pmd_t *pmd;
> +	pte_t *pte;
> +
> +	pgd = pgd_offset_k(addr);
> +	if (!pgd_present(*pgd))
> +		return false;
> +
> +	p4d = p4d_offset(pgd, addr);
> +	if (!p4d_present(*p4d))
> +		return false;
> +
> +	pud = pud_offset(p4d, addr);
> +	if (!pud_present(*pud))
> +		return false;
> +
> +	pmd = pmd_offset(pud, addr);
> +	if (!pmd_present(*pmd))
> +		return false;
> +
> +	pte = pte_offset_kernel(pmd, addr);
> +	return pte_present(*pte);
> +}
> diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
> index 5948218f35c5..4352f08bfbb5 100644
> --- a/arch/x86/include/asm/set_memory.h
> +++ b/arch/x86/include/asm/set_memory.h
> @@ -82,6 +82,7 @@ int set_pages_rw(struct page *page, int numpages);
>   
>   int set_direct_map_invalid_noflush(struct page *page);
>   int set_direct_map_default_noflush(struct page *page);
> +bool kernel_page_present(struct page *page);
>   
>   extern int kernel_set_to_readonly;
>   
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index bc9be96b777f..16f878c26667 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -2226,8 +2226,8 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
>   
>   	arch_flush_lazy_mmu_mode();
>   }
> +#endif /* CONFIG_DEBUG_PAGEALLOC */
>   
> -#ifdef CONFIG_HIBERNATION
>   bool kernel_page_present(struct page *page)
>   {
>   	unsigned int level;
> @@ -2239,8 +2239,6 @@ bool kernel_page_present(struct page *page)
>   	pte = lookup_address((unsigned long)page_address(page), &level);
>   	return (pte_val(*pte) & _PAGE_PRESENT);
>   }
> -#endif /* CONFIG_HIBERNATION */
> -#endif /* CONFIG_DEBUG_PAGEALLOC */
>   
>   int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
>   				   unsigned numpages, unsigned long page_flags)
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ab0ef6bd351d..44b82f22e76a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2937,16 +2937,9 @@ static inline void debug_pagealloc_map_pages(struct page *page,
>   	if (debug_pagealloc_enabled_static())
>   		__kernel_map_pages(page, numpages, enable);
>   }
> -
> -#ifdef CONFIG_HIBERNATION
> -extern bool kernel_page_present(struct page *page);
> -#endif	/* CONFIG_HIBERNATION */
>   #else	/* CONFIG_DEBUG_PAGEALLOC */
>   static inline void debug_pagealloc_map_pages(struct page *page,
>   					     int numpages, int enable) {}
> -#ifdef CONFIG_HIBERNATION
> -static inline bool kernel_page_present(struct page *page) { return true; }
> -#endif	/* CONFIG_HIBERNATION */
>   #endif	/* CONFIG_DEBUG_PAGEALLOC */
>   
>   #ifdef __HAVE_ARCH_GATE_AREA
> diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
> index 860e0f843c12..fe1aa4e54680 100644
> --- a/include/linux/set_memory.h
> +++ b/include/linux/set_memory.h
> @@ -23,6 +23,11 @@ static inline int set_direct_map_default_noflush(struct page *page)
>   {
>   	return 0;
>   }
> +
> +static inline bool kernel_page_present(struct page *page)
> +{
> +	return true;
> +}
>   #endif
>   
>   #ifndef set_mce_nospec
> 

It's somewhat weird to move this to set_memory.h - it's only one 
possible user. I think include/linux/mm.h is a better fit. Ack to making 
it independent of CONFIG_HIBERNATION.

in include/linux/mm.h , I'd prefer:

#if defined(CONFIG_DEBUG_PAGEALLOC) || \
     defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP)
bool kernel_page_present(struct page *page);
#else
static inline bool kernel_page_present(struct page *page)
{
	return true;
}
#endif

-- 
Thanks,

David / dhildenb