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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: 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, bp@alien8.de,
	josh@joshtriplett.org, luto@kernel.org, kai.huang@intel.com,
	rientjes@google.com, cedric.xing@intel.com,
	puiterwijk@redhat.com, linux-security-module@vger.kernel.org,
	Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [PATCH v23 12/24] x86/sgx: Linux Enclave Driver
Date: Tue, 5 Nov 2019 13:11:22 +0200
Message-ID: <20191105111057.GA20879@linux.intel.com> (raw)
In-Reply-To: <20191031211252.GC10507@linux.intel.com>

On Thu, Oct 31, 2019 at 11:12:52PM +0200, Jarkko Sakkinen wrote:
> On Wed, Oct 30, 2019 at 02:30:45AM -0700, Sean Christopherson wrote:
> > Why?  The number of pages processed is effectively returned via the params
> > on any error, e.g. wouldn't it be more appropriate to return -ERESTARTSYS?
> > And I don't see any reason to add an arbitrary cap on the number of pages,
> > e.g. SGX plays nice with the scheduler and signals, and restricting the
> > number of EPC pages available to a process via cgroups (returning -ENOMEM)
> > is a better solution for managing EPC.
> 
> Returning -ENOMEM does not tell you from which page to retry.

API should be robust enough to be able to cap the amount of data
processed with or without cgroups like send(), recv(), read() and
write() are and the call pattern for it must be a loop not a single shot
call for any megalomaniac length.

I'll add @count to address this. This output field will contain the
number of bytes actually written instead of overwriting input
parameters, which is a bad practice in anyway.

We don't need to actually cap to anything but API must be able to
support such scenario. Caller must be prepared to deal with the
situation where the return value is zero but @count < @length.

/Jarkko

  reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-28 21:03 [PATCH v23 00/24] Intel SGX foundations Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 01/24] x86/sgx: Update MAINTAINERS Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 02/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 03/24] x86/cpufeatures: x86/msr: Intel SGX Launch Control " Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 04/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 05/24] x86/sgx: Add SGX microarchitectural data structures Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 06/24] x86/sgx: Add wrappers for ENCLS leaf functions Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 07/24] x86/cpu/intel: Detect SGX supprt Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 08/24] x86/sgx: Enumerate and track EPC sections Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 09/24] x86/sgx: Add functions to allocate and free EPC pages Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 10/24] x86/sgx: Add sgx_einit() for wrapping ENCLS[EINIT] Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 11/24] mm: Introduce vm_ops->may_mprotect() Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 12/24] x86/sgx: Linux Enclave Driver Jarkko Sakkinen
2019-10-29  9:29   ` Jarkko Sakkinen
2019-10-30  9:30     ` Sean Christopherson
2019-10-31 21:12       ` Jarkko Sakkinen
2019-11-05 11:11         ` Jarkko Sakkinen [this message]
2019-11-08  8:20           ` Jarkko Sakkinen
2019-10-30 13:45   ` Stephen Smalley
2019-10-31 21:17     ` Jarkko Sakkinen
2019-11-01 13:16       ` Stephen Smalley
2019-11-01 13:28         ` Stephen Smalley
2019-11-01 15:32           ` Sean Christopherson
2019-11-01 17:16             ` Stephen Smalley
2019-11-08  8:05               ` Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 13/24] selftests/x86: Recurse into subdirectories Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 14/24] selftests/x86: Add a selftest for SGX Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 15/24] x86/sgx: Add provisioning Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 16/24] x86/sgx: Add a page reclaimer Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 17/24] x86/sgx: ptrace() support for the SGX driver Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 18/24] x86/vdso: Add support for exception fixup in vDSO functions Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 19/24] x86/fault: Add helper function to sanitize error code Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 20/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 21/24] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 22/24] selftests/x86: Add vDSO selftest for SGX Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 23/24] docs: x86/sgx: Document microarchitecture Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 24/24] docs: x86/sgx: Document kernel internals Jarkko Sakkinen

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