From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH v16 06/22] x86/cpu/intel: Detect SGX support and update caps appropriately Date: Wed, 7 Nov 2018 17:58:13 +0200 Message-ID: <20181107155813.GA9730@linux.intel.com> References: <20181106134758.10572-1-jarkko.sakkinen@linux.intel.com> <20181106134758.10572-7-jarkko.sakkinen@linux.intel.com> <1541512681.7839.14.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <1541512681.7839.14.camel@intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Sean Christopherson Cc: x86@kernel.org, platform-driver-x86@vger.kernel.org, linux-sgx@vger.kernel.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, Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Konrad Rzeszutek Wilk , David Woodhouse , "Kirill A. Shutemov" , David Wang , "Levin, Alexander (Sasha Levin)" , Jia Zhang , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" List-Id: platform-driver-x86.vger.kernel.org On Tue, Nov 06, 2018 at 05:58:01AM -0800, Sean Christopherson wrote: > On Tue, 2018-11-06 at 15:45 +0200, Jarkko Sakkinen wrote: > > From: Sean Christopherson > > > > Similar to other large Intel features such as VMX and TXT, SGX must be > > explicitly enabled in IA32_FEATURE_CONTROL MSR to be truly usable. > > Clear all SGX related capabilities if SGX is not fully enabled in > > IA32_FEATURE_CONTROL or if the SGX1 instruction set isn't supported > > (impossible on bare metal, theoretically possible in a VM if the VMM is > > doing something weird). > > > > Like SGX itself, SGX Launch Control must be explicitly enabled via a > > flag in IA32_FEATURE_CONTROL. Clear the SGX_LC capability if Launch > > Control is not fully enabled (or obviously if SGX itself is disabled). > > > > Note that clearing X86_FEATURE_SGX_LC creates a bit of a conundrum > > regarding the SGXLEPUBKEYHASH MSRs, as it may be desirable to read the > > MSRs even if they are not writable, e.g. to query the configured key, > > but clearing the capability leaves no breadcrum for discerning whether > > or not the MSRs exist.  But, such usage will be rare (KVM is the only > > known case at this time) and not performance critical, so it's not > > unreasonable to require the use of rdmsr_safe().  Clearing the cap bit > > eliminates the need for an additional flag to track whether or not > > Launch Control is truly enabled, which is what we care about the vast > > majority of the time. > > > > Signed-off-by: Sean Christopherson > > Co-developed-by: Jarkko Sakkinen > > Signed-off-by: Jarkko Sakkinen > > --- > >  arch/x86/kernel/cpu/intel.c | 37 +++++++++++++++++++++++++++++++++++++ > >  1 file changed, 37 insertions(+) > > > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > > index fc3c07fe7df5..8a20a193d399 100644 > > --- a/arch/x86/kernel/cpu/intel.c > > +++ b/arch/x86/kernel/cpu/intel.c > > @@ -596,6 +596,40 @@ static void detect_tme(struct cpuinfo_x86 *c) > >   c->x86_phys_bits -= keyid_bits; > >  } > >   > > +static void detect_sgx(struct cpuinfo_x86 *c) > > +{ > > + unsigned long long fc; > > + > > + rdmsrl(MSR_IA32_FEATURE_CONTROL, fc); > > + if (!(fc & FEATURE_CONTROL_LOCKED)) { > > + pr_err_once("sgx: IA32_FEATURE_CONTROL MSR is not locked\n"); > > + goto out_unsupported; > > + } > > + > > + if (!(fc & FEATURE_CONTROL_SGX_ENABLE)) { > > + pr_err_once("sgx: not enabled in IA32_FEATURE_CONTROL MSR\n"); > > + goto out_unsupported; > > + } > > + > > + if (!cpu_has(c, X86_FEATURE_SGX1)) { > > + pr_err_once("sgx: SGX1 instruction set not supported\n"); > > + goto out_unsupported; > > + } > > + > > + if (!(fc & FEATURE_CONTROL_SGX_LE_WR)) { > > FEATURE_CONTROL_SGX_LE_WR isn't added until patch 13/22.  The patch > can simply be moved earlier in the series if you want to introduce > the full detect_sgx() in a single patch.  The only reason SGX_LE_WR > was added later in the series was to bundle the Launch Control stuff > together. Ugh, sorry. Had this is mind when I started working on v16 changes :-( /Jarkko