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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: "Huang, Kai" <kai.huang@intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	"platform-driver-x86@vger.kernel.org" 
	<platform-driver-x86@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"nhorman@redhat.com" <nhorman@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"suresh.b.siddha@intel.com" <suresh.b.siddha@intel.com>,
	"Ayoun, Serge" <serge.ayoun@intel.com>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"npmccallum@redhat.com" <npmccallum@redhat.com>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
	"Hansen, Dave" <dave.hansen@intel.com>
Subject: Re: [PATCH v13 10/13] x86/sgx: Add sgx_einit() for initializing enclaves
Date: Tue, 4 Sep 2018 07:54:51 -0700	[thread overview]
Message-ID: <20180904145451.GA5233@linux.intel.com> (raw)
In-Reply-To: <105F7BF4D0229846AF094488D65A09893541970F@PGSMSX112.gar.corp.intel.com>

On Mon, Sep 03, 2018 at 04:45:14PM -0700, Huang, Kai wrote:
> > -----Original Message-----
> > From: linux-sgx-owner@vger.kernel.org [mailto:linux-sgx-
> > owner@vger.kernel.org] On Behalf Of Jarkko Sakkinen
> > Sent: Tuesday, September 4, 2018 7:19 AM
> > To: Christopherson, Sean J <sean.j.christopherson@intel.com>
> > Cc: Huang, Kai <kai.huang@intel.com>; platform-driver-x86@vger.kernel.org;
> > x86@kernel.org; nhorman@redhat.com; linux-kernel@vger.kernel.org;
> > tglx@linutronix.de; suresh.b.siddha@intel.com; Ayoun, Serge
> > <serge.ayoun@intel.com>; hpa@zytor.com; npmccallum@redhat.com;
> > mingo@redhat.com; linux-sgx@vger.kernel.org; Hansen, Dave
> > <dave.hansen@intel.com>
> > Subject: Re: [PATCH v13 10/13] x86/sgx: Add sgx_einit() for initializing enclaves
> > 
> > On Fri, Aug 31, 2018 at 11:15:09AM -0700, Sean Christopherson wrote:
> > > On Fri, Aug 31, 2018 at 03:17:03PM +0300, Jarkko Sakkinen wrote:
> > > > On Wed, Aug 29, 2018 at 07:33:54AM +0000, Huang, Kai wrote:
> > > > > [snip..]
> > > > >
> > > > > > > >
> > > > > > > > @@ -38,6 +39,18 @@ static LIST_HEAD(sgx_active_page_list);
> > > > > > > > static DEFINE_SPINLOCK(sgx_active_page_list_lock);
> > > > > > > >  static struct task_struct *ksgxswapd_tsk;  static
> > > > > > > > DECLARE_WAIT_QUEUE_HEAD(ksgxswapd_waitq);
> > > > > > > > +static struct notifier_block sgx_pm_notifier; static u64
> > > > > > > > +sgx_pm_cnt;
> > > > > > > > +
> > > > > > > > +/* The cache for the last known values of
> > > > > > > > +IA32_SGXLEPUBKEYHASHx MSRs
> > > > > > > > for each
> > > > > > > > + * CPU. The entries are initialized when they are first
> > > > > > > > + used by
> > > > > > > > sgx_einit().
> > > > > > > > + */
> > > > > > > > +struct sgx_lepubkeyhash {
> > > > > > > > +	u64 msrs[4];
> > > > > > > > +	u64 pm_cnt;
> > > > > > >
> > > > > > > May I ask why do we need pm_cnt here? In fact why do we need
> > > > > > > suspend staff (namely, sgx_pm_cnt above, and related code in
> > > > > > > this patch) here in this patch? From the patch commit message
> > > > > > > I don't see why we need PM staff here. Please give comment why
> > > > > > > you need PM staff, or you may consider to split the PM staff to another
> > patch.
> > > > > >
> > > > > > Refining the commit message probably makes more sense because
> > > > > > without PM code sgx_einit() would be broken. The MSRs have been reset
> > after waking up.
> > > > > >
> > > > > > Some kind of counter is required to keep track of the power
> > > > > > cycle. When going to sleep the sgx_pm_cnt is increased.
> > > > > > sgx_einit() compares the current value of the global count to
> > > > > > the value in the cache entry to see whether we are in a new power cycle.
> > > > >
> > > > > You mean reset to Intel default? I think we can also just reset
> > > > > the cached MSR values on each power cycle, which would be simpler,
> > IMHO?
> > > >
> > > > I don't really see that much difference in the complexity.
> > >
> > > Tracking the validity of the cache means we're hosed if we miss any
> > > condition that causes the MSRs to be reset.  I think we're better off
> > > assuming the cache can be stale at any time, i.e. don't track power
> > > cyles and instead handle EINIT failure due to INVALID_TOKEN by writing
> > > the cache+MSRs with the desired hash and retrying EINIT.  EINIT is
> > > interruptible and its latency is extremely variable in any case, e.g.
> > > tens of thousands of cycles, so this rarely-hit "slow path" probably
> > > wouldn't affect the worst case latency of EINIT.
> > 
> > Sounds a good refiniment. Pretty good solution to heal from host sleep on the
> > guest VM and then there is no need for driver changes.
> 
> To me either way should be OK, keeping MSR cache or retrying EINIT, since EINIT should not be in performance critical path I think.
> 
> But INVALID_TOKEN is not only returned when MSRs are mismatched, so do you plan to check to rule out other cases that cause INVALID_TOKEN before retrying EINIT, or unconditionally  retry EINIT? And we should only retry once?

I don't see any value in trying to rule out specific causes of
INVALID_TOKEN, but we should only retry EINIT if ret==INVALID_TOKEN
and RDMSR(HASH0) != sgx_lepubkeyhash[0].  Only the first MSR needs to
be checked for validity as they're a package deal, i.e. they'll all be
valid or all be reset.  There shouldn't be a limit on retry attempts,
e.g. the MSRs could theoretically be reset between WRMSR and EINIT.

> 
> Thanks,
> -Kai
> > 
> > /Jarkko

  reply	other threads:[~2018-09-04 14:54 UTC|newest]

Thread overview: 103+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-27 18:53 [PATCH v13 00/13] Intel SGX1 support Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 01/13] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2018-09-03 12:56   ` Andy Shevchenko
2018-09-03 19:10     ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 02/13] x86/cpufeature: Add SGX and SGX_LC CPU features Jarkko Sakkinen
2018-08-28  0:07   ` Huang, Kai
2018-08-28  7:17     ` Jarkko Sakkinen
2018-08-29  7:36       ` Huang, Kai
2018-08-31 12:19         ` Jarkko Sakkinen
2018-08-31 16:18   ` Dr. Greg
2018-08-27 18:53 ` [PATCH v13 03/13] x86/cpufeatures: Add Intel-defined SGX leaf CPUID_12_EAX Jarkko Sakkinen
2018-08-27 19:39   ` Dave Hansen
2018-08-28  7:23     ` Jarkko Sakkinen
2018-08-28 10:21   ` Borislav Petkov
2018-08-28 10:38     ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 04/13] x86/sgx: Architectural structures Jarkko Sakkinen
2018-08-27 19:41   ` Dave Hansen
2018-08-28  8:08     ` Jarkko Sakkinen
2018-09-03 13:16   ` Andy Shevchenko
2018-09-03 19:17     ` Jarkko Sakkinen
2018-09-04 16:04     ` Dave Hansen
2018-09-04 16:06       ` Andy Shevchenko
2018-09-05 17:32       ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 05/13] x86/msr: Add SGX definitions to msr-index.h Jarkko Sakkinen
2018-08-27 19:42   ` Dave Hansen
2018-08-28  8:11     ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 06/13] x86/sgx: Detect Intel SGX Jarkko Sakkinen
2018-08-27 19:53   ` Dave Hansen
2018-08-28  8:28     ` Jarkko Sakkinen
2018-09-03 14:26   ` Andy Shevchenko
2018-09-04  9:56     ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 07/13] x86/sgx: Add data structures for tracking the EPC pages Jarkko Sakkinen
2018-08-27 21:07   ` Dave Hansen
2018-08-28 10:30     ` Jarkko Sakkinen
2018-08-28 16:53       ` Dave Hansen
2018-08-28 21:34         ` Sean Christopherson
2018-08-31 11:13           ` Jarkko Sakkinen
2018-08-31 11:10         ` Jarkko Sakkinen
2018-09-03 14:41   ` Andy Shevchenko
2018-09-04  9:59     ` Jarkko Sakkinen
2018-09-04 17:49     ` Sean Christopherson
2018-09-04 18:01       ` Andy Shevchenko
2018-09-04 18:17         ` Sean Christopherson
2018-09-05 17:36           ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 08/13] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2018-09-03 15:01   ` Andy Shevchenko
2018-09-04 11:09     ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 09/13] x86/sgx: Enclave Page Cache (EPC) memory manager Jarkko Sakkinen
2018-08-27 21:14   ` Dave Hansen
2018-08-28  8:36     ` Jarkko Sakkinen
2018-08-27 21:15   ` Dave Hansen
2018-08-28  8:35     ` Jarkko Sakkinen
2018-08-28 14:07       ` Dave Hansen
2018-08-28 21:22         ` Sean Christopherson
2018-08-28 21:26           ` Dave Hansen
2018-08-28 21:52             ` Sean Christopherson
2018-08-31 11:22           ` Jarkko Sakkinen
2018-09-03 19:02   ` Andy Shevchenko
2018-09-04 15:38     ` Jarkko Sakkinen
2018-09-04 15:45       ` Sean Christopherson
2018-09-11 15:04   ` Sean Christopherson
2018-09-16 11:40     ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 10/13] x86/sgx: Add sgx_einit() for initializing enclaves Jarkko Sakkinen
2018-08-27 21:41   ` Huang, Kai
2018-08-28  7:01     ` Jarkko Sakkinen
2018-08-29  7:33       ` Huang, Kai
2018-08-29 20:33         ` Sean Christopherson
2018-08-29 20:58           ` Huang, Kai
2018-08-29 21:09             ` Sean Christopherson
2018-08-30  1:45               ` Huang, Kai
2018-08-31 17:43                 ` Sean Christopherson
2018-08-31 21:34                   ` Dr. Greg
2018-09-03 19:27                     ` Jarkko Sakkinen
2018-09-03 18:15                 ` Jarkko Sakkinen
2018-08-31 12:17         ` Jarkko Sakkinen
2018-08-31 18:15           ` Sean Christopherson
2018-09-03 19:19             ` Jarkko Sakkinen
2018-09-03 23:45               ` Huang, Kai
2018-09-04 14:54                 ` Sean Christopherson [this message]
2018-09-04 15:30                   ` Jarkko Sakkinen
2018-09-04 16:35                     ` Sean Christopherson
2018-09-04 22:13                       ` Huang, Kai
2018-09-05 17:39                       ` Jarkko Sakkinen
2018-09-04 15:26                 ` Jarkko Sakkinen
2018-09-03 13:53   ` Jann Horn
2018-09-04  9:55     ` Jarkko Sakkinen
2018-09-04 16:05   ` Andy Shevchenko
2018-08-27 18:53 ` [PATCH v13 11/13] platform/x86: Intel SGX driver Jarkko Sakkinen
2018-09-04 17:59   ` Andy Shevchenko
2018-09-05 17:33     ` Jarkko Sakkinen
2018-09-05 17:36       ` Andy Shevchenko
2018-09-06  9:21         ` Jarkko Sakkinen
2018-09-06 17:35           ` Miguel Ojeda
2018-09-07  0:50             ` Joe Perches
2018-09-07 17:02               ` Sean Christopherson
2018-09-10 18:37               ` Jarkko Sakkinen
2018-09-10 21:22                 ` Joe Perches
2018-09-10 18:33             ` Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 12/13] platform/x86: ptrace() support for the " Jarkko Sakkinen
2018-08-27 18:53 ` [PATCH v13 13/13] x86/sgx: Driver documentation Jarkko Sakkinen
2018-08-27 19:40   ` Randy Dunlap
2018-08-28  7:58     ` Jarkko Sakkinen
2018-08-28  8:03   ` Jarkko Sakkinen

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