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

On 2020-02-29 3:33 p.m., Dan Williams wrote:

On Fri, Feb 21, 2020 at 10:25 AM Logan Gunthorpe [off-list ref] wrote:

quoted

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

Cc: Thomas Gleixner <redacted>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 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_<cachemode> 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 <redacted>