Messages in this thread | | | Subject | Re: [RFC/RFT PATCH 2/3] arm64: decouple check whether pfn is normal memory from pfn_valid() | From | David Hildenbrand <> | Date | Thu, 15 Apr 2021 11:31:26 +0200 |
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On 14.04.21 22:29, Mike Rapoport wrote: > On Wed, Apr 14, 2021 at 05:58:26PM +0200, David Hildenbrand wrote: >> On 08.04.21 07:14, Anshuman Khandual wrote: >>> >>> On 4/7/21 10:56 PM, Mike Rapoport wrote: >>>> From: Mike Rapoport <rppt@linux.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 ? >>> >>>> >>>> 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@linux.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. 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. > > Yeah, at the moment NOMAP is very much arm specific so I'd keep it this way > for now. > >> 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. > > In my current version (to be posted soon) I've started with > pfn_lineary_mapped() but then ended up with pfn_mapped() to make it > "upward" compatible with architectures that use direct rather than linear > map :)
And even that is moot. It doesn't tell you if a PFN is *actually* mapped (hello secretmem).
I'd suggest to just use memblock_is_map_memory() in arch specific code. Then it's clear what we are querying exactly and what the semantics might be.
-- Thanks,
David / dhildenb
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