On Wed, Jun 20, 2018 at 07:47:02AM -0700, Dave Hansen wrote:
On 06/13/2018 05:44 PM, Ram Pai wrote:
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
...
if (flags)
pkey_assert(read_pkey_reg() > orig_pkey_reg);
pkey_assert(read_pkey_reg() >= orig_pkey_reg);}
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);