From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Daney Subject: Re: [PATCH v3 5/5] mips/kvm: Fix ABI by moving manipulation of CP0 registers to KVM_{G,S}ET_MSRS Date: Tue, 21 May 2013 09:34:22 -0700 Message-ID: <519BA20E.6080101@caviumnetworks.com> References: <1369083686-27524-1-git-send-email-ddaney.cavm@gmail.com> <1369083686-27524-6-git-send-email-ddaney.cavm@gmail.com> <20130521153752.GD14287@redhat.com> <519B9EF2.8020107@caviumnetworks.com> <20130521162811.GE14287@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: David Daney , , , , Sanjay Lal , , David Daney To: Gleb Natapov Return-path: In-Reply-To: <20130521162811.GE14287@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 05/21/2013 09:28 AM, Gleb Natapov wrote: > On Tue, May 21, 2013 at 09:21:06AM -0700, David Daney wrote: >> On 05/21/2013 08:37 AM, Gleb Natapov wrote: >>> On Mon, May 20, 2013 at 02:01:26PM -0700, David Daney wrote: >>>> From: David Daney >>>> >>>> Because not all 256 CP0 registers are ever implemented, we need a >>>> different method of manipulating them. Use the >>>> KVM_GET_MSRS/KVM_SET_MSRS mechanism as x86 does for its MSRs. >>>> >>> Have you looked at KVM_(GET|SET)_ONE_REG interface (not used by x86, but is >>> used bu arm/ppc/s390). It looks like it is more suitable for your case. >>> Actually you can use it instead of KVM_(GET|SET)_REGS for all registers. >> >> Yes, I suppose it could be used. One problem it has is that there >> is no way to query the set of supported registers. > KVM_GET_REG_LIST OK, I guess we can switch to KVM_GET_REG_LIST/KVM_(GET|SET)_ONE_REG. I will revise this patch. Thanks. > >> Also you have to >> make multiple calls to set multiple registers, which involves >> vcpu_{load,put} for each register. >> > How often this happens on the fast path on mips? Rarely, if ever once, the VCPU is running. Only when initializing the VCPU do we need to set a bunch of registers. > On x86 this never > happens on the fast path so it uses KVM_(GET|SET)_REGS mostly for > historical reasons. > >> We will definitely implement it for all the FP and General Purpose >> registers. >> >>> >>>> Code related to implementing KVM_GET_MSRS/KVM_SET_MSRS is consolidated >> > > -- > Gleb. >