| Message ID | 20220617043135.426897-1-rashmica@linux.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | powerpc/signal: Update comment for clarity | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 23 jobs. |
On Fri, 17 Jun 2022 14:31:35 +1000, Rashmica Gupta wrote: > 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. > > > [...] Applied to powerpc/next. [1/1] powerpc/signal: Update comment for clarity https://git.kernel.org/powerpc/c/e4787e71ae2de3f60bc04fe09d1be4ef628b6c68 cheers
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));
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 <rashmica@linux.ibm.com> --- arch/powerpc/kernel/signal_64.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)