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Message-ID: <YG6cFKKimksg+FX3@kernel.org>
Date: Thu, 8 Apr 2021 09:00:52 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-arm-kernel@...ts.infradead.org,
Ard Biesheuvel <ardb@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
David Hildenbrand <david@...hat.com>,
Marc Zyngier <maz@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Will Deacon <will@...nel.org>, kvmarm@...ts.cs.columbia.edu,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC/RFT PATCH 2/3] arm64: decouple check whether pfn is normal
memory from pfn_valid()
On Thu, Apr 08, 2021 at 10:44:58AM +0530, Anshuman Khandual wrote:
>
> On 4/7/21 10:56 PM, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@...ux.ibm.com>
> >
> > The intended semantics of pfn_valid() is to verify whether there is a
> > struct page for the pfn in question and nothing else.
>
> Should there be a comment affirming this semantics interpretation, above the
> generic pfn_valid() in include/linux/mmzone.h ?
Yeah, that would have been helpful :)
> >
> > Yet, on arm64 it is used to distinguish memory areas that are mapped in the
> > linear map vs those that require ioremap() to access them.
> >
> > Introduce a dedicated pfn_is_memory() to perform such check and use it
> > where appropriate.
> >
> > Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> > ---
> > arch/arm64/include/asm/memory.h | 2 +-
> > arch/arm64/include/asm/page.h | 1 +
> > arch/arm64/kvm/mmu.c | 2 +-
> > arch/arm64/mm/init.c | 6 ++++++
> > arch/arm64/mm/ioremap.c | 4 ++--
> > arch/arm64/mm/mmu.c | 2 +-
> > 6 files changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> > index 0aabc3be9a75..7e77fdf71b9d 100644
> > --- a/arch/arm64/include/asm/memory.h
> > +++ b/arch/arm64/include/asm/memory.h
> > @@ -351,7 +351,7 @@ static inline void *phys_to_virt(phys_addr_t x)
> >
> > #define virt_addr_valid(addr) ({ \
> > __typeof__(addr) __addr = __tag_reset(addr); \
> > - __is_lm_address(__addr) && pfn_valid(virt_to_pfn(__addr)); \
> > + __is_lm_address(__addr) && pfn_is_memory(virt_to_pfn(__addr)); \
> > })
> >
> > void dump_mem_limit(void);
> > diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
> > index 012cffc574e8..32b485bcc6ff 100644
> > --- a/arch/arm64/include/asm/page.h
> > +++ b/arch/arm64/include/asm/page.h
> > @@ -38,6 +38,7 @@ void copy_highpage(struct page *to, struct page *from);
> > typedef struct page *pgtable_t;
> >
> > extern int pfn_valid(unsigned long);
> > +extern int pfn_is_memory(unsigned long);
> >
> > #include <asm/memory.h>
> >
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 8711894db8c2..ad2ea65a3937 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -85,7 +85,7 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
> >
> > static bool kvm_is_device_pfn(unsigned long pfn)
> > {
> > - return !pfn_valid(pfn);
> > + return !pfn_is_memory(pfn);
> > }
> >
> > /*
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 3685e12aba9b..258b1905ed4a 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -258,6 +258,12 @@ int pfn_valid(unsigned long pfn)
> > }
> > EXPORT_SYMBOL(pfn_valid);
> >
> > +int pfn_is_memory(unsigned long pfn)
> > +{
> > + return memblock_is_map_memory(PFN_PHYS(pfn));
> > +}
> > +EXPORT_SYMBOL(pfn_is_memory);> +
>
> Should not this be generic though ? There is nothing platform or arm64
> specific in here.
As NOMAP itself is quite ARM specific, this check is currently only
relevant for arm64 and maybe arm32.
But probably having an EXPORT_SYMBOL wrapper for memblock_is_map_memory(),
say in memblock does make sense for all architectures that have
KEEP_MEMBLOCK.
> Wondering as pfn_is_memory() just indicates that the
> pfn is linear mapped, should not it be renamed as pfn_is_linear_memory()
> instead ? Regardless, it's fine either way.
Yeah, I agree that naming could be better here. I think that for a generic name
we'd need pfn_is_directly_mapped() so that it can be used on x86 ;-)
> > static phys_addr_t memory_limit = PHYS_ADDR_MAX;
> >
> > /*
> > diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
> > index b5e83c46b23e..82a369b22ef5 100644
> > --- a/arch/arm64/mm/ioremap.c
> > +++ b/arch/arm64/mm/ioremap.c
> > @@ -43,7 +43,7 @@ static void __iomem *__ioremap_caller(phys_addr_t phys_addr, size_t size,
> > /*
> > * Don't allow RAM to be mapped.
> > */
> > - if (WARN_ON(pfn_valid(__phys_to_pfn(phys_addr))))
> > + if (WARN_ON(pfn_is_memory(__phys_to_pfn(phys_addr))))
> > return NULL;
> >
> > area = get_vm_area_caller(size, VM_IOREMAP, caller);
> > @@ -84,7 +84,7 @@ EXPORT_SYMBOL(iounmap);
> > void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size)
> > {
> > /* For normal memory we already have a cacheable mapping. */
> > - if (pfn_valid(__phys_to_pfn(phys_addr)))
> > + if (pfn_is_memory(__phys_to_pfn(phys_addr)))
> > return (void __iomem *)__phys_to_virt(phys_addr);
> >
> > return __ioremap_caller(phys_addr, size, __pgprot(PROT_NORMAL),
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 5d9550fdb9cf..038d20fe163f 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -81,7 +81,7 @@ void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd)
> > pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> > unsigned long size, pgprot_t vma_prot)
> > {
> > - if (!pfn_valid(pfn))
> > + if (!pfn_is_memory(pfn))
> > return pgprot_noncached(vma_prot);
> > else if (file->f_flags & O_SYNC)
> > return pgprot_writecombine(vma_prot);
> >
--
Sincerely yours,
Mike.
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