From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [RFC PATCH] arm64: KVM: remove fpsimd save/restore from the world switch Date: Fri, 10 Apr 2015 11:08:38 +0100 Message-ID: <5527A126.6080202@arm.com> References: <1428598439-5217-1-git-send-email-marc.zyngier@arm.com> <55278CAD.70302@redhat.com> <552793CF.8050904@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Paolo Bonzini , "kvm@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.cs.columbia.edu" To: Peter Maydell Return-path: In-Reply-To: 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 10/04/15 11:01, Peter Maydell wrote: > On 10 April 2015 at 10:11, Marc Zyngier wrote: >> I did some experimentations on arm64 a long while ago (see the >> kvm-arm64/lazy-fp branch in my tree), and it wasn't that great, >> apparently because aarch64 userspace tends to be much more FP happy than >> aarch32, but I'm not completely sure about it. > > Was that with the buggy version of the toolchain that had > incorrect costs and so was much more inclined to spill > integer values into the FPU than it should have been? > It might be worth retesting with a freshly compiled > userspace some day... It definitely was with a very old toolchain and an even older userspace. I'll respin the branch when I get some thime. Thanks, M. -- Jazz is not dead. It just smells funny...