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SubjectRe: [PATCH v3 4/4] arch, mm: make kernel_page_present() always available
On Mon, Nov 02, 2020 at 10:28:14AM +0100, David Hildenbrand wrote:
> 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.

Semantically this is a part of direct map manipulation, that's primarily
why I put it into set_memory.h

> in include/linux/mm.h , I'd prefer:
>
> #if defined(CONFIG_DEBUG_PAGEALLOC) || \
> defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP)

The second reason was to avoid this ^
and the third is -7 lines to include/linux/mm.h :)

> bool kernel_page_present(struct page *page);
> #else
> static inline bool kernel_page_present(struct page *page)
> {
> return true;
> }
> #endif
>
> --
> Thanks,
>
> David / dhildenb
>
>

--
Sincerely yours,
Mike.

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