On 8/27/2021 11:21 AM, Borislav Petkov wrote:
On Fri, Aug 27, 2021 at 11:10:31AM -0700, Yu, Yu-cheng wrote:
Because on context switches the whole xstates are switched together,
we need to make sure all are in registers.
There's context switch code which does that already.
Why would shstk_setup() be responsible for switching the whole extended
states buffer instead of only the shadow stack stuff only?
Right now, the kernel does lazy restore, and it waits until right before
a task goes back to ring-3 to restore xstates. If a task needs to write
to any xstate registers before that (e.g. for signals), it restores the
whole xstates first and clears TIF_NEED_FPU_LOAD, which will prevent
xstates being restored again later.
