RE: [Xen-devel] [patch 3/3] VT-d cleanup: correct way to submit command to GCMD register

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

The patch attached in previous mail is obsolete. Attached the right one. Thanks.

Regards,
Weidong


Han, Weidong wrote:
> 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>

gcmd-2.patch
Description: gcmd-2.patch

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