On Wed, Jun 20, 2018 at 07:47:02AM -0700, Dave Hansen wrote:

On 06/13/2018 05:44 PM, Ram Pai wrote:

quoted

If the flag is 0, no bits will be set. Hence we cant expect
the resulting bitmap to have a higher value than what it
was earlier

...

quoted

 	if (flags)
-		pkey_assert(read_pkey_reg() > orig_pkey_reg);
+		pkey_assert(read_pkey_reg() >= orig_pkey_reg);
 	dprintf1("END<---%s(%d, 0x%x)\n", __func__,
 		pkey, flags);
 }

This is the kind of thing where I'd love to hear the motivation and
background.  This "disable a key that was already disabled" operation
obviously doesn't happen today.  What motivated you to change it now?

On powerpc, hardware supports READ_DISABLE and WRITE_DISABLE.
ACCESS_DISABLE is basically READ_DISABLE|WRITE_DISABLE on powerpc.

If access disable is called on a key followed by a write disable, the
second operation becomes a nop. In such cases, 
       read_pkey_reg() == orig_pkey_reg


Hence the code above is modified to 
	pkey_assert(read_pkey_reg() >= orig_pkey_reg);


-- 
Ram Pai