From: Josh Poimboeuf <jpoimboe@redhat.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH v8] Command-line
Date: Mon, 9 Jul 2018 18:00:15 -0500 [thread overview]
Message-ID: <20180709230015.bds6d7snkyl4kk67@treble> (raw)
In-Reply-To: <nycvar.YFH.7.76.1807100046050.997@cbobk.fhfr.pm>
On Tue, Jul 10, 2018 at 12:53:12AM +0200, speck for Jiri Kosina wrote:
> On Mon, 9 Jul 2018, speck for Josh Poimboeuf wrote:
>
> > > @@ -13235,6 +13243,20 @@ static int __init vmx_setup_l1d_flush(void)
> > > {
> > > struct page *page;
> > >
> > > + /* Take the l1tf= command line parameter into account */
> > > + switch (l1tf_mitigation) {
> > > + case L1TF_MITIGATION_FULL:
> > > + case L1TF_MITIGATION_FULL_FORCE:
> > > + /* Respect the FLUSH ALWAYS module param */
> > > + if (vmentry_l1d_flush == VMENTER_L1D_FLUSH_NEVER)
> > > + vmentry_l1d_flush = VMENTER_L1D_FLUSH_COND;
> > > + break;
> > > + default:
> > > + break;
> > > + }
> > > +
> > > + l1tf_vmx_mitigation = vmentry_l1d_flush;
> > > +
> > > if (vmentry_l1d_flush == VMENTER_L1D_FLUSH_NEVER ||
> > > !boot_cpu_has_bug(X86_BUG_L1TF) ||
> > > vmx_l1d_use_msr_save_list())
> >
> > Quoting my earlier comment:
> >
> > I'm not sure about this for the non-force case. If somebody goes to the
> > trouble of setting the vmx option, it seems like we should honor that.
> >
> > However, I think it *does* make sense for the force case.
> >
> > I'm not sure if my comment was overlooked, or just disagreed with. The
> > fix should be as simple as removing the following line:
> >
> > case L1TF_MITIGATION_FULL:
> >
> > Or if you and Thomas disagree with this change, I can live with that.
>
> So Thomas didn't have a strong option on that, and I frankly don't either.
>
> So far we've mostly related the the 'force' for the full mitigation to SMT
> disabling, with your proposed change it'd have a slightly broader meaning,
> but it'd make sense as well.
>
> One would hope it's really just a corner case though, as it'd happen
> *only* if the administrator of the system explicitly changes l1tf to
> 'full*', and explicitly changes the kvm parameter to 'never', which is a
> combination that by itself doesn't make too much sense .. so "anything
> could happen".
>
> So I am fine either way.
Yeah, the combination doesn't really make much sense. Eh, whatever...
--
Josh
prev parent reply other threads:[~2018-07-09 23:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-09 22:24 [MODERATED] [PATCH v8] Command-line Jiri Kosina
2018-07-09 22:44 ` [MODERATED] " Josh Poimboeuf
2018-07-09 22:53 ` Jiri Kosina
2018-07-09 23:00 ` Josh Poimboeuf [this message]
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