From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mario Smarduch Subject: Re: [PATCH 3/3] KVM/arm64: enable enhanced armv8 fp/simd lazy switch Date: Sat, 14 Nov 2015 15:04:23 -0800 Message-ID: <5647BDF7.5070209@samsung.com> References: <1446242193-8424-1-git-send-email-m.smarduch@samsung.com> <1446242193-8424-4-git-send-email-m.smarduch@samsung.com> <20151105150255.GD5819@cbox> <5641288B.90105@samsung.com> <20151110111822.GC12968@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: marc.zyngier@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org To: Christoffer Dall Return-path: In-reply-to: <20151110111822.GC12968@cbox> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On 11/10/2015 3:18 AM, Christoffer Dall wrote: > On Mon, Nov 09, 2015 at 03:13:15PM -0800, Mario Smarduch wrote: >> >> >> On 11/5/2015 7:02 AM, Christoffer Dall wrote: >>> On Fri, Oct 30, 2015 at 02:56:33PM -0700, Mario Smarduch wrote: [....] >> kern_hyp_va x0 >> add x2, x0, #VCPU_CONTEXT >> mrs x1, fpexec32_el2 >> str x1, [x2, #CPU_SYSREG_OFFSET(FPEXC32_EL2)] >> ret >> >> Of course each hyp call has additional overhead, at a high exit to >> vcpu_put ratio hyp call appears better. But all this is very >> highly dependent on exit rate and fp/simd usage. IMO hyp call >> works better under extreme loads should be pretty close >> for general loads. >> >> Any thoughts? >> > I think the typical case will be lots of exits and few > vcpu_load/vcpu_put, and I think it's reasonable to write the code that > way. Yes, especially for RT guests where vCPU is pinned. Thanks. > > That should also be much better for VHE. > > So I would go that direction. > > Thanks, > -Christoffer >