Re: [PATCH v3 4/7] x86/mm: Introduce _set_memory_prot()

[Logan Gunthorpe]

On 2020-02-29 3:33 p.m., Dan Williams wrote:
> On Fri, Feb 21, 2020 at 10:25 AM Logan Gunthorpe  wrote:
>>
>> For use in the 32bit arch_add_memory() to set the pgprot type of the
>> memory to add.
>>
>> Cc: Thomas Gleixner 
>> Cc: Ingo Molnar 
>> Cc: Borislav Petkov 
>> Cc: "H. Peter Anvin" 
>> Cc: x...@kernel.org
>> Cc: Dave Hansen 
>> Cc: Andy Lutomirski 
>> Cc: Peter Zijlstra 
>> Signed-off-by: Logan Gunthorpe 
>> ---
>>  arch/x86/include/asm/set_memory.h | 1 +
>>  arch/x86/mm/pat/set_memory.c  | 7 +++
>>  2 files changed, 8 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/set_memory.h 
>> b/arch/x86/include/asm/set_memory.h
>> index 64c3dce374e5..0aca959cf9a4 100644
>> --- a/arch/x86/include/asm/set_memory.h
>> +++ b/arch/x86/include/asm/set_memory.h
>> @@ -34,6 +34,7 @@
>>   * The caller is required to take care of these.
>>   */
>>
>> +int _set_memory_prot(unsigned long addr, int numpages, pgprot_t prot);
> 
> I wonder if this should be separated from the naming convention of the
> other routines because this is only an internal helper for code paths
> where the prot was established by an upper layer. For example, I
> expect that the kernel does not want new usages to make the mistake of
> calling:
> 
>_set_memory_prot(..., pgprot_writecombine(pgprot))
> 
> ...instead of
> 
> _set_memory_wc()
> 
> I'm thinking just a double underscore rename (__set_memory_prot) and a
> kerneldoc comment for that  pointing people to use the direct
> _set_memory_ helpers.

Thanks! Will do. Note, though, that even _set_memory_wc() is an internal
x86-specific function. But the extra comment and underscore still make
sense.

> With that you can add:
> 
> Reviewed-by: Dan Williams 
> 

Re: [PATCH v3 4/7] x86/mm: Introduce _set_memory_prot()

[Dan Williams]

On Fri, Feb 21, 2020 at 10:25 AM Logan Gunthorpe  wrote:
>
> For use in the 32bit arch_add_memory() to set the pgprot type of the
> memory to add.
>
> Cc: Thomas Gleixner 
> Cc: Ingo Molnar 
> Cc: Borislav Petkov 
> Cc: "H. Peter Anvin" 
> Cc: x...@kernel.org
> Cc: Dave Hansen 
> Cc: Andy Lutomirski 
> Cc: Peter Zijlstra 
> Signed-off-by: Logan Gunthorpe 
> ---
>  arch/x86/include/asm/set_memory.h | 1 +
>  arch/x86/mm/pat/set_memory.c  | 7 +++
>  2 files changed, 8 insertions(+)
>
> diff --git a/arch/x86/include/asm/set_memory.h 
> b/arch/x86/include/asm/set_memory.h
> index 64c3dce374e5..0aca959cf9a4 100644
> --- a/arch/x86/include/asm/set_memory.h
> +++ b/arch/x86/include/asm/set_memory.h
> @@ -34,6 +34,7 @@
>   * The caller is required to take care of these.
>   */
>
> +int _set_memory_prot(unsigned long addr, int numpages, pgprot_t prot);

I wonder if this should be separated from the naming convention of the
other routines because this is only an internal helper for code paths
where the prot was established by an upper layer. For example, I
expect that the kernel does not want new usages to make the mistake of
calling:

   _set_memory_prot(..., pgprot_writecombine(pgprot))

...instead of

_set_memory_wc()

I'm thinking just a double underscore rename (__set_memory_prot) and a
kerneldoc comment for that  pointing people to use the direct
_set_memory_ helpers.

With that you can add:

Reviewed-by: Dan Williams 

[PATCH v3 4/7] x86/mm: Introduce _set_memory_prot()

[Logan Gunthorpe]

For use in the 32bit arch_add_memory() to set the pgprot type of the
memory to add.

Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: x...@kernel.org
Cc: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Peter Zijlstra 
Signed-off-by: Logan Gunthorpe 
---
 arch/x86/include/asm/set_memory.h | 1 +
 arch/x86/mm/pat/set_memory.c  | 7 +++
 2 files changed, 8 insertions(+)

diff --git a/arch/x86/include/asm/set_memory.h 
b/arch/x86/include/asm/set_memory.h
index 64c3dce374e5..0aca959cf9a4 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -34,6 +34,7 @@
  * The caller is required to take care of these.
  */
 
+int _set_memory_prot(unsigned long addr, int numpages, pgprot_t prot);
 int _set_memory_uc(unsigned long addr, int numpages);
 int _set_memory_wc(unsigned long addr, int numpages);
 int _set_memory_wt(unsigned long addr, int numpages);
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index c4aedd00c1ba..2ba83d53d835 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1792,6 +1792,13 @@ static inline int cpa_clear_pages_array(struct page 
**pages, int numpages,
CPA_PAGES_ARRAY, pages);
 }
 
+int _set_memory_prot(unsigned long addr, int numpages, pgprot_t prot)
+{
+   return change_page_attr_set_clr(, numpages, prot,
+   __pgprot(~pgprot_val(prot)), 0, 0,
+   NULL);
+}
+
 int _set_memory_uc(unsigned long addr, int numpages)
 {
/*
-- 
2.20.1