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[91.12.100.112]) by smtp.gmail.com with ESMTPSA id y31sm5805675wmp.46.2021.04.14.08.58.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Apr 2021 08:58:26 -0700 (PDT) Subject: Re: [RFC/RFT PATCH 2/3] arm64: decouple check whether pfn is normal memory from pfn_valid() To: Anshuman Khandual , Mike Rapoport , linux-arm-kernel@lists.infradead.org Cc: Ard Biesheuvel , Catalin Marinas , Marc Zyngier , Mark Rutland , Mike Rapoport , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210407172607.8812-1-rppt@kernel.org> <20210407172607.8812-3-rppt@kernel.org> <4a788546-b854-fd35-644a-f1d9075a9a78@arm.com> From: David Hildenbrand Organization: Red Hat Message-ID: <9c0956f0-494e-5c6b-bdc2-d4213afd5e2f@redhat.com> Date: Wed, 14 Apr 2021 17:58:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <4a788546-b854-fd35-644a-f1d9075a9a78@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.04.21 07:14, Anshuman Khandual wrote: > > On 4/7/21 10:56 PM, Mike Rapoport wrote: >> From: Mike Rapoport >> >> 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 ? > >> >> 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 >> --- >> 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 >> >> 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. 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. TBH, I dislike (generic) pfn_is_memory(). It feels like we're mixing concepts. NOMAP memory vs !NOMAP memory; even NOMAP is some kind of memory after all. pfn_is_map_memory() would be more expressive, although still sub-optimal. We'd actually want some kind of arm64-specific pfn_is_system_memory() or the inverse pfn_is_device_memory() -- to be improved. -- Thanks, David / dhildenb