From: "Huang, Kai" <kai.huang@intel.com>
To: "Chatre, Reinette" <reinette.chatre@intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"jarkko@kernel.org" <jarkko@kernel.org>
Cc: "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
"Christopherson,, Sean" <seanjc@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>
Subject: Re: [PATCH] x86/intel: Clear SGX bit if both SGX driver and KVM SGX are not enabled
Date: Mon, 12 Sep 2022 20:54:20 +0000 [thread overview]
Message-ID: <b68befe6d17cd60a18cc29d7ca2187d91c19f9bc.camel@intel.com> (raw)
In-Reply-To: <28d7a4bf-591f-3afa-b9ea-526a14abc587@intel.com>
On Mon, 2022-09-12 at 07:34 -0700, Dave Hansen wrote:
> On 9/12/22 07:31, Reinette Chatre wrote:
> >
> > On 9/12/2022 3:47 AM, Jarkko Sakkinen wrote:
> > > On Fri, Sep 09, 2022 at 08:08:53PM +1200, Kai Huang wrote:
> > > > Currently on platform which has SGX enabled, if CONFIG_X86_SGX is not
> > > > enabled, the X86_FEATURE_SGX is not cleared, resulting in /proc/cpuinfo
> > > > shows "sgx" feature. This is not desired.
> > > >
> > > > Clear SGX feature bit if both SGX driver and KVM SGX are not enabled in
> > > > init_ia32_feat_ctl().
> > > >
> > > > Signed-off-by: Kai Huang <kai.huang@intel.com>
> > > Is it a pattern that flags are cleared when they are disabled by the
> > > kernel? I don't know the answer for this.
>
> There's no good pattern.
>
> But, one guideline is that the X86_FEATURE_*'s are for the *kernel*.
> They are *not* for userspace. The fact that the features are exposed to
> userspace in cpuinfo is unfortunate, but it doesn't change our guideline.
>
> So, if this patch is done only for the benefit of userspace, I don't
> think we should apply it.
It's not done for the userspace. AFAICT no one is complaining about this. I
just happened to see this and thought it's a right thing to do.
Also, in my other reply to this thread I put one reason that I think it's
reasonable:
"
But for SGX even the current upstream code clears SGX feature in some
conditions, for example, when SGX_LC is disabled by BIOS (in which case only KVM
SGX can be supported) and KVM SGX is also disabled, i.e. due to
CONFIG_X86_SGX_KVM isn't set:
if (!(msr & FEAT_CTL_SGX_LC_ENABLED) && enable_sgx_driver) {
if (!enable_sgx_kvm) {
pr_err_once("SGX Launch Control is locked. Disable SGX.\n");
clear_cpu_cap(c, X86_FEATURE_SGX);
else {
...
}
}
So I think it makes sense to clear SGX if both SGX driver and KVM SGX are not
enabled by the kernel.
"
--
Thanks,
-Kai
prev parent reply other threads:[~2022-09-12 20:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-09 8:08 [PATCH] x86/intel: Clear SGX bit if both SGX driver and KVM SGX are not enabled Kai Huang
2022-09-09 11:05 ` Huang, Kai
2022-09-09 12:11 ` Dave Hansen
2022-09-12 3:09 ` Huang, Kai
2022-09-12 10:47 ` Jarkko Sakkinen
2022-09-12 14:31 ` Reinette Chatre
2022-09-12 14:34 ` Dave Hansen
2022-09-12 20:54 ` Huang, Kai [this message]
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