[Xen-devel] [patch 0/3] VT-d: code cleanup

["Han, Weidong" <weidong.han@xxxxxxxxx>]

We started to do some cleanup on VT-d code. You will see more cleanup patches 
in coming weeks.

This patchset includes following patches:

1. remove-useless.patch: 
  remove global variable "vtd_enabled", which is redundant. "iommu_enabled" is 
enough. And also removed useless global variables qi_ctrl and ir_ctrl, which 
are not used at all.

2. iommu-wait-op.patch:
  when set some registers of VT-d, it must wait for hardware completion. There 
are lots of duplicated code to do that. This patch defines a macro for it, thus 
it is much cleaner.

3. gcmd.patch: 
  per VT-d spec, software should submit only one "incremental" command at a 
time to Global Command reigster. Current implementation uses a variable (gcmd) 
to record the state of Global Status register. It's error prone. A good 
algorithm to use is as follows, whenver software needs to submit a command:
        Read current value of Global Status Register (X);               //  
This tells what is the current state of commands enabled in hardware
        X = Bitwise OR the new command bit to X;                // The only new 
bit set in X is the one new command we are going to issue
        Write X  to Global Command register;                    // Submit the 
command
        Poll Global Status register until it has new value of X ;       // Poll 
until command is done


Signed-off-by: Weidong Han <weidong.han@xxxxxxxxx>


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