>It conflicts with your new code. We can have an argument on whether IB should >follow how SSB is being handled. Before that is settled,
Thank you for the information. It conflicts but I think users who read the below document get confused. Documentation/userspace-api/spec_ctrl.rst. Especially, seccomp users must know the difference of this implicit specification because both IB and SSB are force disabled simultaneously when seccomp is enabled without SECCOMP_FILTER_FLAG_SPEC_ALLOW on x86. -----Original Message----- From: Waiman Long <long...@redhat.com> Sent: Thursday, June 4, 2020 12:40 AM To: Tada, Kenta (Sony) <kenta.t...@sony.com>; x...@kernel.org; t...@linutronix.de; mi...@redhat.com; b...@alien8.de; h...@zytor.com; jpoim...@redhat.com; pet...@infradead.org; tony.l...@intel.com; pawan.kumar.gu...@linux.intel.com Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/speculation: Check whether speculation is force disabled On 6/3/20 3:12 AM, Tada, Kenta (Sony) wrote: > Once PR_SPEC_FORCE_DISABLE is set, users cannot set PR_SPEC_ENABLE. > This commit checks whether PR_SPEC_FORCE_DISABLE was previously set. > > Signed-off-by: Kenta Tada <kenta.t...@sony.com> > --- > arch/x86/kernel/cpu/bugs.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > index ed54b3b21c39..678ace157035 100644 > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -1173,6 +1173,9 @@ static int ib_prctl_set(struct task_struct *task, > unsigned long ctrl) > if (spectre_v2_user == SPECTRE_V2_USER_STRICT || > spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED) > return -EPERM; > + /* If speculation is force disabled, enable is not allowed */ > + if (task_spec_ib_force_disable(task)) > + return -EPERM; > task_clear_spec_ib_disable(task); > task_update_spec_tif(task); > break; There is a comment up a few lines about this: /* * Indirect branch speculation is always allowed when * mitigation is force disabled. */ It conflicts with your new code. We can have an argument on whether IB should follow how SSB is being handled. Before that is settled, Nacked-by: Waiman Long <long...@redhat.com>
