Re: [patch] i386: remove IOPL check on task switch

Zachary Amsden
2006-11-04T19:19:54Z

Chuck Ebbert wrote:
> In-Reply-To: <454B850C.3050402@vmware.com>
>
> On Fri, 03 Nov 2006 10:06:04 -0800, Zachary Amsden wrote:
>
>
>> Chuck Ebbert wrote:
>>
>>> IOPL is implicitly saved and restored on task switch,
>>> so explicit check is no longer needed.
>>>
>> Nack. This is used for paravirt-ops kernels that use IOPL'd userspace.
>>
>
> How does that work? In the stock kernel, anything done by
> the call to set_iopl_mask() (that was removed by the patch)
> will be nullified by the 'popfl' at the end of the switch_to()
> macro.
>

Who put a popfl back in switch_to? I took it out some time ago. It
should not be there. The only reason for it was to stop IOPL leaking
from one process to another from a sleep during a sysenter based system
call.

Zach