Messages in this thread | | | Subject | Re: [PATCH] x86/speculation: Check whether speculation is force disabled | From | Waiman Long <> | Date | Wed, 3 Jun 2020 11:39:38 -0400 |
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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.Tada@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 <longman@redhat.com>
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