From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Huang, Kai" Subject: Re: [intel-sgx-kernel-dev] [PATCH 08/10] kvm: vmx: add guest's IA32_SGXLEPUBKEYHASHn runtime switch support Date: Tue, 16 May 2017 11:56:38 +1200 Message-ID: <478d9303-00b7-4f29-6124-0c1433851952@linux.intel.com> References: <20170508052434.3627-1-kai.huang@linux.intel.com> <20170508052434.3627-9-kai.huang@linux.intel.com> <58dcdb2d-6894-b0a3-8d6f-2ab752fd6d22@linux.intel.com> <20170515124622.piupyk57vjdoppl5@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm list , Radim Krcmar , haim.cohen@intel.com, "intel-sgx-kernel-dev@lists.01.org" , Paolo Bonzini To: Jarkko Sakkinen , Andy Lutomirski Return-path: Received: from mga11.intel.com ([192.55.52.93]:38832 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752987AbdEOX4p (ORCPT ); Mon, 15 May 2017 19:56:45 -0400 In-Reply-To: <20170515124622.piupyk57vjdoppl5@intel.com> Sender: kvm-owner@vger.kernel.org List-ID: On 5/16/2017 12:46 AM, Jarkko Sakkinen wrote: > On Thu, May 11, 2017 at 08:28:37PM -0700, Andy Lutomirski wrote: >> [resending due to some kind of kernel.org glitch -- sorry if anyone >> gets duplicates] >> >> On Thu, May 11, 2017 at 5:32 PM, Huang, Kai wrote: >>> My current patch is based on this assumption. For KVM guest, naturally, we >>> will write the cached value to real MSRs when vcpu is scheduled in. For >>> host, SGX driver should write its own value to MSRs when it performs EINIT >>> for LE. >> >> This seems unnecessarily slow (perhaps *extremely* slow) to me. I >> would propose a totally different solution: >> >> Have a percpu variable that stores the current SGXLEPUBKEYHASH along >> with whatever lock is needed (probably just a mutex). Users of EINIT >> will take the mutex, compare the percpu variable to the desired value, >> and, if it's different, do WRMSR and update the percpu variable. > > This is exactly what I've been suggesting internally: trap EINIT and > check the value and write conditionally. > > I think this would be the best starting point. OK. Assuming we are going to have this percpu variable for IA32_SGXLEPUBKEYHASHn, I suppose KVM also will update guest's value to this percpu variable after KVM writes guest's value to hardware MSR? And host (SGX driver) need to do the same thing (check the value and write conditionally), correct? Thanks, -Kai > > /Jarkko >