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: Tue, 12 Jan 2016 16:57:15 -0800 Message-ID: <5695A0EB.5020609@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> <56943D29.3000002@samsung.com> <20160112141207.GF15554@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: marc.zyngier@arm.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org To: Christoffer Dall Return-path: In-reply-to: <20160112141207.GF15554@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 1/12/2016 6:12 AM, Christoffer Dall wrote: > On Mon, Jan 11, 2016 at 03:39:21PM -0800, Mario Smarduch wrote: >> >> >> 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. >> > > If you have to guests with CONFIG_VFPV3 but your host doesn't have > CONFIG_VFPV3, you will never context-switch the VFP registers between > the two VMs, and mayhem will ensue. > > Unless I'm missing something very obvious? Hi Christoffer, - on host I disabled VFP/VFPv3 and got a lot of Illegal instructions and many other problems. Perhaps disabling for armv7 this option may need re-evaluation. - Enabling VFPv3 on host and running guest with no vfpv3 appears to work with few glitches. - and vpfv3 host/guest works just fine. Appears disabling vfpv3 on armv7 requires another investigation (atleast on my end). BTW this is on fast models. - Mario > > -Christoffer > From mboxrd@z Thu Jan 1 00:00:00 1970 From: m.smarduch@samsung.com (Mario Smarduch) Date: Tue, 12 Jan 2016 16:57:15 -0800 Subject: [PATCH v6 1/6] arm/arm64: KVM: Introduce armv7 fp/simd vcpu fields and helpers In-Reply-To: <20160112141207.GF15554@cbox> References: <1451166900-3711-1-git-send-email-m.smarduch@samsung.com> <1451166900-3711-2-git-send-email-m.smarduch@samsung.com> <20160110163204.GD30867@cbox> <56943D29.3000002@samsung.com> <20160112141207.GF15554@cbox> Message-ID: <5695A0EB.5020609@samsung.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 1/12/2016 6:12 AM, Christoffer Dall wrote: > On Mon, Jan 11, 2016 at 03:39:21PM -0800, Mario Smarduch wrote: >> >> >> 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. >> > > If you have to guests with CONFIG_VFPV3 but your host doesn't have > CONFIG_VFPV3, you will never context-switch the VFP registers between > the two VMs, and mayhem will ensue. > > Unless I'm missing something very obvious? Hi Christoffer, - on host I disabled VFP/VFPv3 and got a lot of Illegal instructions and many other problems. Perhaps disabling for armv7 this option may need re-evaluation. - Enabling VFPv3 on host and running guest with no vfpv3 appears to work with few glitches. - and vpfv3 host/guest works just fine. Appears disabling vfpv3 on armv7 requires another investigation (atleast on my end). BTW this is on fast models. - Mario > > -Christoffer >