On Fri, Aug 27, 2021 at 11:37:34AM -0700, Yu, Yu-cheng wrote:
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.
shstk_setup() allocates a shadow stack for the task and puts its pointer
in MSR_IA32_PL3_SSP.
What does that have to do with a task having to write any xstate
registers?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette