From: Borislav Petkov <bp@alien8.de>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
linux-sgx@vger.kernel.org, akpm@linux-foundation.org,
dave.hansen@intel.com, nhorman@redhat.com, npmccallum@redhat.com,
serge.ayoun@intel.com, shay.katz-zamir@intel.com,
haitao.huang@intel.com, andriy.shevchenko@linux.intel.com,
tglx@linutronix.de, kai.svahn@intel.com, josh@joshtriplett.org,
luto@kernel.org, kai.huang@intel.com, rientjes@google.com,
cedric.xing@intel.com, Kai Huang <kai.huang@linux.intel.com>,
Haim Cohen <haim.cohen@intel.com>
Subject: Re: [PATCH v22 02/24] x86/cpufeatures: x86/msr: Intel SGX Launch Control hardware bits
Date: Wed, 25 Sep 2019 10:51:56 +0200 [thread overview]
Message-ID: <20190925085156.GA3891@zn.tnic> (raw)
In-Reply-To: <20190924202210.GC16218@linux.intel.com>
On Tue, Sep 24, 2019 at 01:22:10PM -0700, Sean Christopherson wrote:
> The approach we chose (patch 04, which we were discussing) is to disable
> SGX if SGX_LE_WR is not set, i.e. disallow SGX unless the hash MSRs exist
> and are fully writable.
Hmm, so I see
+ if (!(fc & FEATURE_CONTROL_SGX_LE_WR)) {
+ pr_info_once("sgx: The launch control MSRs are not writable\n");
+ goto err_msrs_rdonly;
which clears only X86_FEATURE_SGX_LC but leaves the other three feature
bits set?!
If you'd want to disable SGX then you'd need to jump to the
err_unsupported label and get rid of the err_msrs_rdonly one.
Or am I missing something?
> WRMSR will #GP if FEATURE_CONTROL is locked (bit 0), e.g. attempting to
> set SGX_LE_WR will trap if FEATURE_CONTROL was locked by BIOS.
Right.
> And conversely, the various enable bits in FEATURE_CONTROL don't
> take effect until FEATURE_CONTROL is locked, e.g. the LE hash MSRs
> aren't writable if FEATURE_CONTROL is unlocked, regardless of whether
> SGX_LE_WR is set.
Ok. We want them writable.
> Sadly, because FEATURE_CONTROL must be locked to fully enable SGX, the
> reality is that any BIOS that supports SGX will lock FEATURE_CONTROL.
That's fine. The question is, would OEMs leave the hash MSRs writable?
If, as you say above, we clear SGX feature bit - not only
X86_FEATURE_SGX_LC - when the MSRs are not writable, then we're fine.
Platforms sticking their own hash in there won't be supported but I
guess their aim is not to be supported in Linux anyway.
> That's the status quo today as well since VMX (and SMX/TXT) is also
> enabled via FEATURE_CONTROL. KVM does have logic to enable VMX and lock
> FEATURE_CONTROL if the MSR isn't locked, but AIUI that exists only to work
> with old BIOSes.
>
> If we want to support setting and locking FEATURE_CONTROL in the extremely
> unlikely scenario that BIOS left it unlocked, the proper change would be
I wouldn't be too surprised if this happened. BIOS is very inventive.
> One note on Launch Control that isn't covered in the SDM: the LE hash
> MSRs can also be written before SGX is activated. SGX activation must
> occur before FEATURE_CONTROL is locked, meaning BIOS can set the LE
> hash MSRs to a non-intel and then lock FEATURE_CONTROL with SGX_LE_WR=0.
This is exactly what I'm afraid of. The OEM vendors locking this down.
> Heh, why stop at 4? 12_EBX, 12_1_ECX and 12_1_EDX are effectively feature
> leafs as well, although the kernel can ignore them for the most part.
Yeah, we're mentally prepared for the feature bit space explosion. :)
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2019-09-25 8:53 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-03 14:26 [PATCH v22 00/24] Intel SGX foundations Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 01/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2019-09-24 15:28 ` Borislav Petkov
2019-09-24 16:11 ` Sean Christopherson
2019-09-24 16:25 ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 02/24] x86/cpufeatures: x86/msr: Intel SGX Launch Control " Jarkko Sakkinen
2019-09-24 15:52 ` Borislav Petkov
2019-09-24 20:22 ` Sean Christopherson
2019-09-25 8:51 ` Borislav Petkov [this message]
2019-09-25 17:18 ` Sean Christopherson
2019-09-25 18:31 ` Borislav Petkov
2019-09-25 19:08 ` Sean Christopherson
2019-09-27 16:11 ` Jarkko Sakkinen
2019-09-25 14:09 ` Jarkko Sakkinen
2019-09-25 14:10 ` Jarkko Sakkinen
2019-09-25 14:38 ` Jarkko Sakkinen
2019-09-25 15:19 ` Borislav Petkov
2019-09-25 16:49 ` Sean Christopherson
2019-09-25 17:28 ` Borislav Petkov
2019-09-25 18:18 ` Sean Christopherson
2019-09-03 14:26 ` [PATCH v22 03/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2019-09-24 16:04 ` Borislav Petkov
2019-09-25 14:16 ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 04/24] x86/cpu/intel: Detect SGX supprt Jarkko Sakkinen
2019-09-24 16:13 ` Borislav Petkov
2019-09-24 17:43 ` Sean Christopherson
2019-09-24 18:21 ` Borislav Petkov
2019-09-25 14:46 ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 05/24] x86/sgx: Add ENCLS architectural error codes Jarkko Sakkinen
2019-09-27 10:20 ` Borislav Petkov
2019-09-27 16:08 ` Jarkko Sakkinen
2019-09-27 17:20 ` Sean Christopherson
2019-10-01 20:23 ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 06/24] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2019-09-27 16:27 ` Borislav Petkov
2019-10-01 19:10 ` Jarkko Sakkinen
2019-10-01 20:39 ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 07/24] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2019-10-04 9:45 ` Borislav Petkov
2019-10-04 18:56 ` Jarkko Sakkinen
2019-10-08 4:04 ` Sean Christopherson
2019-10-08 7:18 ` Borislav Petkov
2019-10-08 13:35 ` Sean Christopherson
2019-10-08 14:56 ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 08/24] x86/sgx: Enumerate and track EPC sections Jarkko Sakkinen
2019-10-05 9:26 ` Borislav Petkov
2019-10-07 11:58 ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 09/24] x86/sgx: Add functions to allocate and free EPC pages Jarkko Sakkinen
2019-10-05 16:44 ` Borislav Petkov
2019-10-07 14:50 ` Sean Christopherson
2019-10-08 9:09 ` Borislav Petkov
2019-10-08 13:31 ` Sean Christopherson
2019-10-07 17:55 ` Jarkko Sakkinen
2019-10-07 18:09 ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 10/24] x86/sgx: Add sgx_einit() for wrapping ENCLS[EINIT] Jarkko Sakkinen
2019-10-08 17:30 ` Borislav Petkov
2019-10-08 17:45 ` Sean Christopherson
2019-10-08 17:46 ` Sean Christopherson
2019-10-08 17:53 ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 11/24] mm: Introduce vm_ops->may_mprotect() Jarkko Sakkinen
2019-10-08 17:41 ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 12/24] x86/sgx: Linux Enclave Driver Jarkko Sakkinen
2019-10-08 17:59 ` Borislav Petkov
2019-10-08 18:17 ` Sean Christopherson
2019-10-08 19:19 ` Borislav Petkov
2019-09-03 14:26 ` [PATCH v22 13/24] x86/sgx: Add provisioning Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 14/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 15/24] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 16/24] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2019-10-02 23:18 ` Jarkko Sakkinen
2019-10-02 23:45 ` Jarkko Sakkinen
2019-10-04 0:03 ` Sean Christopherson
2019-10-04 18:49 ` Jarkko Sakkinen
2019-10-04 0:15 ` Sean Christopherson
2019-10-04 18:52 ` Jarkko Sakkinen
2019-10-05 15:54 ` Sean Christopherson
2019-10-07 7:57 ` Jarkko Sakkinen
2019-10-07 8:10 ` Jarkko Sakkinen
2019-10-07 12:04 ` Jarkko Sakkinen
2019-10-08 4:54 ` Sean Christopherson
2019-10-05 18:39 ` Sean Christopherson
2019-10-07 8:01 ` Jarkko Sakkinen
2019-10-06 23:38 ` Jarkko Sakkinen
2019-10-06 23:40 ` Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 17/24] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 18/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 19/24] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 20/24] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 21/24] selftests/x86: Recurse into subdirectories Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 22/24] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2019-09-03 14:26 ` [PATCH v22 23/24] docs: x86/sgx: Document microarchitecture Jarkko Sakkinen
2019-09-27 18:15 ` Randy Dunlap
2019-09-03 14:26 ` [PATCH v22 24/24] docs: x86/sgx: Document kernel internals Jarkko Sakkinen
2019-09-27 17:07 ` Randy Dunlap
2019-10-01 19:34 ` Jarkko Sakkinen
2019-09-13 20:38 ` [PATCH v22 00/24] Intel SGX foundations Dave Hansen
2019-09-14 13:41 ` Jarkko Sakkinen
2019-09-14 15:32 ` Dave Hansen
2019-09-16 5:23 ` Jarkko Sakkinen
2019-09-24 17:20 ` Andy Lutomirski
2019-09-25 14:32 ` Jarkko Sakkinen
2019-10-02 23:42 ` Jarkko Sakkinen
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