The comment being referred to was deleted in commit af1bbc3dd3d5 ("powerpc:
Remove UP only lazy floating point and vector optimisations").Add a bit more detail so it's clear why we need to clear the FP/VEC/VSX bits here. Signed-off-by: Rashmica Gupta <[email protected]> --- arch/powerpc/kernel/signal_64.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c index 472596a109e2..86bb5bb4c143 100644 --- a/arch/powerpc/kernel/signal_64.c +++ b/arch/powerpc/kernel/signal_64.c @@ -377,9 +377,12 @@ static long notrace __unsafe_restore_sigcontext(struct task_struct *tsk, sigset_ unsafe_get_user(set->sig[0], &sc->oldmask, efault_out); /* - * Force reload of FP/VEC. - * This has to be done before copying stuff into tsk->thread.fpr/vr - * for the reasons explained in the previous comment. + * Force reload of FP/VEC/VSX so userspace sees any changes. + * Clear these bits from the user process' MSR before copying into the + * thread struct. If we are rescheduled or preempted and another task + * uses FP/VEC/VSX, and this process has the MSR bits set, then the + * context switch code will save the current CPU state into the + * thread_struct - possibly overwriting the data we are updating here. */ regs_set_return_msr(regs, regs->msr & ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX)); -- 2.35.3
