From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Subject: Re: [PATCH v3 5/8] KVM:VMX: Pass through host CET related MSRs to Guest. Date: Mon, 4 Mar 2019 19:21:27 -0800 Message-ID: <20190305032127.GA23534@linux.intel.com> References: <20190225132716.6982-1-weijiang.yang@intel.com> <20190225132716.6982-6-weijiang.yang@intel.com> <20190304185326.GE17120@linux.intel.com> <20190304100714.GA3683@local-michael-cet-test.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: pbonzini@redhat.com, rkrcmar@redhat.com, jmattson@google.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, mst@redhat.com, yu-cheng.yu@intel.com, Zhang Yi Z To: Yang Weijiang Return-path: Content-Disposition: inline In-Reply-To: <20190304100714.GA3683@local-michael-cet-test.sh.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, Mar 04, 2019 at 06:07:14PM +0800, Yang Weijiang wrote: > On Mon, Mar 04, 2019 at 10:53:27AM -0800, Sean Christopherson wrote: > > On Mon, Feb 25, 2019 at 09:27:13PM +0800, Yang Weijiang wrote: > > > The CET runtime settings, i.e., CET state control bits(IA32_U_CET/ > > > IA32_S_CET), CET SSP(IA32_PL3_SSP/IA32_PL0_SSP) and SSP table address > > > (IA32_INTERRUPT_SSP_TABLE_ADDR) are task/thread specific, therefore, > > > OS needs to save/restore the states properly during context switch, > > > e.g., task/thread switching, interrupt/exception handling, it uses > > > xsaves/xrstors to achieve that. > > > > > > The difference between VMCS CET area fields and xsave CET area, is that > > > the former is for state retention during Guest/Host context > > > switch while the latter is for state retention during OS execution. > > > > > > Linux currently doesn't support CPL1 and CPL2, so SSPs for these level > > > are skipped here. > > > > But don't we want to allow a guest to access the MSRs regardless of > > the host kernel's behavior? > > > Do you see any necessity of exposing the access to guest? No, but isn't exposing them to the guest effectively free since XSAVES and XRSTORS will always save/restore them along with SSP0 and SSP3?