On Thu, Nov 25, 2021 at 03:25:09PM +0100, Thomas Gleixner wrote:

On Tue, Aug 03 2021 at 21:32, ira weiny wrote:

quoted

@@ -200,16 +200,14 @@ __setup("init_pkru=", setup_init_pkru);
  */
 u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags)
 {
-	int pkey_shift = pkey * PKR_BITS_PER_PKEY;
-
 	/*  Mask out old bit values */
-	pk_reg &= ~(((1 << PKR_BITS_PER_PKEY) - 1) << pkey_shift);
+	pk_reg &= ~PKR_PKEY_MASK(pkey);
 
 	/*  Or in new values */
 	if (flags & PKEY_DISABLE_ACCESS)
-		pk_reg |= PKR_AD_BIT << pkey_shift;
+		pk_reg |= PKR_AD_KEY(pkey);
 	if (flags & PKEY_DISABLE_WRITE)
-		pk_reg |= PKR_WD_BIT << pkey_shift;
+		pk_reg |= PKR_WD_KEY(pkey);

I'm not seeing how this is improving that code. Quite the contrary.

Fair enough.  Even more so when using the code you suggested for pkey_update_pkval().

In that case it boils down to:

diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index eb6d6b872652..b7127329d115 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c

@@ -198,7 +198,7 @@ __setup("init_pkru=", setup_init_pkru);
  */
 u32 pkey_update_pkval(u32 pkval, int pkey, u32 accessbits)
 {
-        int shift = pkey * PKR_BITS_PER_PKEY;
+        int shift = PKR_PKEY_SHIFT(pkey);
 
         if (WARN_ON_ONCE(accessbits & ~PKEY_ACCESS_MASK))
                 accessbits &= PKEY_ACCESS_MASK;

Better?

As to the reason of why to put this patch after the other one.  Why would I
improve the old pre-refactoring code only to throw it away when moving it to
pkey_update_pkval()?  This reasoning is even stronger when pkey_update_pkval()
is implemented.

I agree with Dan regarding the macros though.  I think they make it easier to
see what is going on without dealing with masks and shifts directly.  But I can
remove this patch if you feel that strongly about it.

Ira

Thanks,

        tglx