On 14.04.21 22:29, Mike Rapoport wrote:

On Wed, Apr 14, 2021 at 05:58:26PM +0200, David Hildenbrand wrote:

quoted

On 08.04.21 07:14, Anshuman Khandual wrote:

quoted

On 4/7/21 10:56 PM, Mike Rapoport wrote:

quoted

From: Mike Rapoport <redacted>

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 ?

quoted

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 <redacted>
---
   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.

quoted

  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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