From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mario Smarduch Subject: Re: [PATCH v6 1/6] arm/arm64: KVM: Introduce armv7 fp/simd vcpu fields and helpers Date: Mon, 11 Jan 2016 15:39:21 -0800 Message-ID: <56943D29.3000002@samsung.com> References: <1451166900-3711-1-git-send-email-m.smarduch@samsung.com> <1451166900-3711-2-git-send-email-m.smarduch@samsung.com> <20160110163204.GD30867@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 3BE3E49ADB for ; Mon, 11 Jan 2016 18:35:25 -0500 (EST) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id P07M9zJIUFx2 for ; Mon, 11 Jan 2016 18:35:23 -0500 (EST) Received: from usmailout4.samsung.com (mailout4.w2.samsung.com [211.189.100.14]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 6136049A9E for ; Mon, 11 Jan 2016 18:35:22 -0500 (EST) Received: from uscpsbgm1.samsung.com (u114.gpu85.samsung.co.kr [203.254.195.114]) by usmailout4.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0O0T00FJKB1MNV30@usmailout4.samsung.com> for kvmarm@lists.cs.columbia.edu; Mon, 11 Jan 2016 18:39:22 -0500 (EST) In-reply-to: <20160110163204.GD30867@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 To: Christoffer Dall Cc: marc.zyngier@arm.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: kvmarm@lists.cs.columbia.edu On 1/10/2016 8:32 AM, Christoffer Dall wrote: > Hi Mario, > > I spotted one more potential issue... > > On Sat, Dec 26, 2015 at 01:54:55PM -0800, Mario Smarduch wrote: >> Add helper functions to enable access to fp/smid on guest entry and save host >> fpexc on vcpu put, check if fp/simd registers are dirty and add new vcpu >> fields. >> >> Signed-off-by: Mario Smarduch >> --- >> arch/arm/include/asm/kvm_emulate.h | 42 ++++++++++++++++++++++++++++++++++++ >> arch/arm/include/asm/kvm_host.h | 6 ++++++ >> arch/arm64/include/asm/kvm_emulate.h | 8 +++++++ >> 3 files changed, 56 insertions(+) >> >> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h >> index 3095df0..d4d9da1 100644 >> --- a/arch/arm/include/asm/kvm_emulate.h >> +++ b/arch/arm/include/asm/kvm_emulate.h >> @@ -24,6 +24,8 @@ >> #include >> #include >> #include >> +#include >> +#include "../vfp/vfpinstr.h" >> >> unsigned long *vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num); >> unsigned long *vcpu_spsr(struct kvm_vcpu *vcpu); >> @@ -255,4 +257,44 @@ static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu, >> } >> } >> >> +#ifdef CONFIG_VFPv3 >> +/* Called from vcpu_load - save fpexc and enable guest access to fp/simd unit */ >> +static inline void vcpu_trap_vfp_enable(struct kvm_vcpu *vcpu) >> +{ >> + u32 fpexc; >> + >> + /* Save host fpexc, and enable guest access to fp unit */ >> + fpexc = fmrx(FPEXC); >> + vcpu->arch.host_fpexc = fpexc; >> + fpexc |= FPEXC_EN; >> + fmxr(FPEXC, fpexc); >> + >> + /* Configure HCPTR to trap on tracing and fp/simd access */ >> + vcpu->arch.hcptr = HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11); >> +} >> + >> +/* Called from vcpu_put - restore host fpexc */ >> +static inline void vcpu_restore_host_fpexc(struct kvm_vcpu *vcpu) >> +{ >> + fmxr(FPEXC, vcpu->arch.host_fpexc); >> +} >> + >> +/* If trap bits are reset then fp/simd registers are dirty */ >> +static inline bool vcpu_vfp_isdirty(struct kvm_vcpu *vcpu) >> +{ >> + return !(vcpu->arch.hcptr & (HCPTR_TCP(10) | HCPTR_TCP(11))); >> +} >> +#else >> +static inline void vcpu_trap_vfp_enable(struct kvm_vcpu *vcpu) >> +{ >> + vcpu->arch.hcptr = HCPTR_TTA; > > Is it correct not to trap VFP registers when the host kernel does not > have CONFIG_VFPv3? I think this is a change in functionality compared > to the current kernels is it not? With CPU_V7 VFPv3 gets selected, without it fp should be emulated, with exceptions taken in guest kernel. I don't see a reason why fp hcptr access should be enabled in that case. > > Thanks, > -Christoffer >