From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Subject: Re: [PATCH v17 18/23] platform/x86: Intel SGX driver
Date: Tue, 18 Dec 2018 03:39:18 +0200
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To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>, Dave Hansen <dave.hansen@intel.com>, X86 ML <x86@kernel.org>, Platform Driver <platform-driver-x86@vger.kernel.org>, linux-sgx@vger.kernel.org, nhorman@redhat.com, npmccallum@redhat.com, "Ayoun, Serge" <serge.ayoun@intel.com>, shay.katz-zamir@intel.com, Haitao Huang <haitao.huang@linux.intel.com>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Thomas Gleixner <tglx@linutronix.de>, "Svahn, Kai" <kai.svahn@intel.com>, mark.shanahan@intel.com, Suresh Siddha <suresh.b.siddha@intel.com>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Darren Hart <dvhart@infradead.org>, Andy Shevchenko <andy@infradead.org>, "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <linux-kernel@vge>
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On Mon, Dec 17, 2018 at 02:20:48PM -0800, Sean Christopherson wrote:
> The only potential hiccup I can see is the build flow.  Currently,
> EADD+EEXTEND is done via a work queue to avoid major performance issues
> (10x regression) when userspace is building multiple enclaves in parallel
> using goroutines to wrap Cgo (the issue might apply to any M:N scheduler,
> but I've only confirmed the Golang case).  The issue is that allocating
> an EPC page acts like a blocking syscall when the EPC is under pressure,
> i.e. an EPC page isn't immediately available.  This causes Go's scheduler
> to thrash and tank performance[1].

I don't see any major issues having that kthread. All the code that
maps the enclave would be removed.

I would only allow to map enclave to process address space after the
enclave has been initialized i.e. SGX_IOC_ENCLAVE_ATTACH.

/Jarkko