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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Jethro Beekman <jethro@fortanix.com>,
	x86@kernel.org, linux-sgx@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Andy Lutomirski <luto@amacapital.net>,
	Cedric Xing <cedric.xing@intel.com>,
	akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
	asapek@google.com, bp@alien8.de, chenalexchen@google.com,
	conradparker@google.com, cyhanish@google.com,
	dave.hansen@intel.com, haitao.huang@intel.com,
	kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com,
	ludloff@google.com, luto@kernel.org, nhorman@redhat.com,
	npmccallum@redhat.com, puiterwijk@redhat.com,
	rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com,
	mikko.ylinen@intel.com
Subject: Re: [PATCH v39 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call
Date: Wed, 7 Oct 2020 06:14:02 +0300
Message-ID: <20201007031402.GA143690@linux.intel.com> (raw)
In-Reply-To: <20201007011738.GE28981@linux.intel.com>

On Tue, Oct 06, 2020 at 06:17:38PM -0700, Sean Christopherson wrote:
> On Wed, Oct 07, 2020 at 03:22:36AM +0300, Jarkko Sakkinen wrote:
> > On Tue, Oct 06, 2020 at 04:21:29PM -0700, Sean Christopherson wrote:
> > > On Tue, Oct 06, 2020 at 08:28:19PM +0300, Jarkko Sakkinen wrote:
> > > > On Tue, Oct 06, 2020 at 08:15:32AM -0700, Sean Christopherson wrote:
> > > > > On Tue, Oct 06, 2020 at 10:30:16AM +0200, Jethro Beekman wrote:
> > > > > > On 2020-10-06 04:57, Sean Christopherson wrote:
> > > > > > > On Sat, Oct 03, 2020 at 07:50:56AM +0300, Jarkko Sakkinen wrote:
> > > > > > >> +struct sgx_enclave_run {
> > > > > > >> +  __u64 tcs;
> > > > > > >> +  __u64 user_handler;
> > > > > > >> +  __u64 user_data;
> > > > > > >> +  __u32 leaf;
> > > > > > >
> > > > > > > I am still very strongly opposed to omitting exit_reason.  It is not at all
> > > > > > > difficult to imagine scenarios where 'leaf' alone is insufficient for the
> > > > > > > caller or its handler to deduce why the CPU exited the enclave.  E.g. see
> > > > > > > Jethro's request for intercepting interrupts.
> > > > > >
> > > > > > Not entirely sure what this has to do with my request, I just expect to see
> > > > > > leaf=ERESUME in this case, I think? E.g. as you would see in EAX when calling
> > > > > > ENCLU.
> > > > > 
> > > > > But how would you differentiate from the case that an exception occured in
> > > > > the enclave?  That will also transfer control with leaf=ERESUME.  If there
> > > > > was a prior exception and userspace didn't zero out the struct, there would
> > > > > be "valid" data in the exception fields.
> > > > > 
> > > > > An exit_reason also would allow retrofitting the exception fields into a
> > > > > union, i.e. the fields are valid if and only if exit_reason is exception.
> > > > 
> > > > Let's purge this a bit. Please remark where my logic goes wrong. I'm
> > > > just explaining how I've deduced the whole thing.
> > > > 
> > > > The information was encoded in v38 version of the vDSO was exactly this:
> > > > 
> > > > - On normal EEXIT, it got the value 0.
> > > > - Otherwise, it got the value 1.
> > > > 
> > > > The leaf, then embdded to struct sgx_exception but essentially the same
> > > > field got the value from EAX, and the value that EAX had was only
> > > > written on exception path.
> > > > 
> > > > Thus, I deduced that if you write $EEXIT to leaf on synchrous exit you
> > > > get the same information content, nothing gets overwritten. I.e. you
> > > > can make same conclusions as you would with those two struct fields.
> > > 
> > > And then a third flavor comes along, e.g. Jethro's request interrupt case,
> > > and exit_reason can also return '2'.  How do you handle that with only the
> > > leaf?
> > 
> > I'm listening. How was that handled before? I saw only '0' and '1'.  Can
> > you bring some context on that? I did read the emails that were swapped
> > when the run structure was added but I'm not sure what is the exact
> > differentiator. Maybe I'm missing something.
> 
> https://patchwork.kernel.org/patch/11719889/

Thank you.

There's aboslutely nothing that is blocking adding such support for such
AEP handling in the current implementation. SGX_SYNCHRONOUS_EXIT is just
another name for EEXIT. Even if that was in place, you'd need to
separate normal and interrupt. Tristate is useless here. As far as I'm
concerned, no bottlenecks have been created.

/Jarkko

  reply index

Thread overview: 117+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-03  4:50 [PATCH v39 00/24] Intel SGX foundations Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 01/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2020-10-19 14:10   ` Dave Hansen
2020-10-19 17:49     ` Sean Christopherson
2020-10-03  4:50 ` [PATCH v39 02/24] x86/cpufeatures: x86/msr: Add Intel SGX Launch Control " Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 03/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 04/24] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 05/24] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2020-10-19 14:30   ` Dave Hansen
2020-10-19 17:38     ` Sean Christopherson
2020-10-19 17:48       ` Dave Hansen
2020-10-19 17:53         ` Sean Christopherson
2020-10-19 17:58           ` Dave Hansen
2020-10-03  4:50 ` [PATCH v39 06/24] x86/cpu/intel: Detect SGX support Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 07/24] x86/cpu/intel: Add nosgx kernel parameter Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 08/24] x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections Jarkko Sakkinen
2020-10-19  8:45   ` Jarkko Sakkinen
2020-10-19 12:39     ` Borislav Petkov
2020-10-23  9:01       ` Jarkko Sakkinen
2020-10-19 13:40     ` Dave Hansen
2020-10-23  9:03       ` Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 09/24] x86/sgx: Add __sgx_alloc_epc_page() and sgx_free_epc_page() Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 10/24] mm: Add 'mprotect' hook to struct vm_operations_struct Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 11/24] x86/sgx: Add SGX enclave driver Jarkko Sakkinen
2020-10-03 14:39   ` Greg KH
2020-10-04 14:32     ` Jarkko Sakkinen
2020-10-04 15:01       ` Jarkko Sakkinen
2020-10-05  9:42       ` Greg KH
2020-10-05 12:42         ` Jarkko Sakkinen
2020-10-07 18:09           ` Haitao Huang
2020-10-07 19:26             ` Greg KH
2020-10-09  6:44               ` Jarkko Sakkinen
2020-10-14 20:16                 ` Dave Hansen
2020-10-05  8:45     ` Christoph Hellwig
2020-10-05 11:42       ` Jarkko Sakkinen
2020-10-05 11:50         ` Greg KH
2020-10-05 14:23           ` Jarkko Sakkinen
2020-10-05 15:02             ` Greg KH
2020-10-05 16:40               ` Dave Hansen
2020-10-05 20:02                 ` Jarkko Sakkinen
2020-10-09  7:10     ` Pavel Machek
2020-10-09  7:21       ` Greg KH
2020-10-09  8:21         ` Pavel Machek
2020-10-03 19:54   ` Matthew Wilcox
2020-10-04 21:50     ` Jarkko Sakkinen
2020-10-04 22:02       ` Jarkko Sakkinen
2020-10-04 22:27       ` Matthew Wilcox
2020-10-04 23:41         ` Jarkko Sakkinen
2020-10-05  1:30           ` Matthew Wilcox
2020-10-05  3:06             ` Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 12/24] x86/sgx: Add SGX_IOC_ENCLAVE_CREATE Jarkko Sakkinen
2020-10-16 17:07   ` Dave Hansen
2020-10-18  4:26     ` Jarkko Sakkinen
2020-10-19 20:21       ` Dave Hansen
2020-10-19 20:48         ` Sean Christopherson
2020-10-03  4:50 ` [PATCH v39 13/24] x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES Jarkko Sakkinen
2020-10-16 21:25   ` Dave Hansen
2020-10-18  5:03     ` Jarkko Sakkinen
2020-10-19  7:03       ` Jarkko Sakkinen
2020-10-19 20:48       ` Dave Hansen
2020-10-19 21:15         ` Sean Christopherson
2020-10-19 21:44           ` Dave Hansen
2020-10-23 10:11             ` Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 14/24] x86/sgx: Add SGX_IOC_ENCLAVE_INIT Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 15/24] x86/sgx: Add SGX_IOC_ENCLAVE_PROVISION Jarkko Sakkinen
2020-10-20 15:48   ` Dave Hansen
2020-10-23 10:14     ` Jarkko Sakkinen
2020-10-20 21:19   ` Dave Hansen
2020-10-23 10:17     ` Jarkko Sakkinen
2020-10-23 14:19       ` Dave Hansen
2020-10-24 11:34         ` Jarkko Sakkinen
2020-10-24 15:47           ` Andy Lutomirski
2020-10-24 20:23             ` Jarkko Sakkinen
2020-10-27 10:38               ` Dr. Greg
2020-10-23 14:23       ` Jethro Beekman
2020-10-24 11:40         ` Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 16/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2020-10-03  5:22   ` Haitao Huang
2020-10-03 13:32     ` Jarkko Sakkinen
2020-10-03 18:23       ` Haitao Huang
2020-10-04 22:39         ` Jarkko Sakkinen
2020-10-07 17:25           ` Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 17/24] x86/sgx: Add ptrace() support for the SGX driver Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 18/24] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 19/24] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 20/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call Jarkko Sakkinen
2020-10-06  2:57   ` Sean Christopherson
2020-10-06  8:30     ` Jethro Beekman
2020-10-06 15:15       ` Sean Christopherson
2020-10-06 17:28         ` Jarkko Sakkinen
2020-10-06 23:21           ` Sean Christopherson
2020-10-07  0:22             ` Jarkko Sakkinen
2020-10-07  1:17               ` Sean Christopherson
2020-10-07  3:14                 ` Jarkko Sakkinen [this message]
2020-10-07  4:34                   ` Sean Christopherson
2020-10-07  7:39                     ` Jarkko Sakkinen
2020-10-07  8:04                       ` Jarkko Sakkinen
2020-10-07 15:25                       ` Sean Christopherson
2020-10-07 17:08                         ` Jarkko Sakkinen
2020-10-07 17:13                           ` Jarkko Sakkinen
2020-10-06 15:49       ` Jarkko Sakkinen
2020-10-06 15:36     ` Jarkko Sakkinen
2020-10-06 21:39     ` Jarkko Sakkinen
2020-10-07  0:23       ` Jarkko Sakkinen
2020-10-17  1:48   ` Andy Lutomirski
2020-10-17 21:02     ` Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 22/24] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2020-10-12 16:50   ` Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 23/24] docs: x86/sgx: Document SGX micro architecture and kernel internals Jarkko Sakkinen
2020-10-03  4:50 ` [PATCH v39 24/24] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2020-10-16 21:04   ` Dave Hansen
2020-10-18  4:27     ` Jarkko Sakkinen
2020-10-03 14:32 ` [PATCH v39 00/24] Intel SGX foundations Greg KH
2020-10-03 14:53   ` Jarkko Sakkinen
2020-10-15 19:06 ` Dave Hansen
2020-10-17 20:43   ` Jarkko Sakkinen

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