From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v2 05/10] KVM: arm: introduce kvm_arch_setup/clear_debug() Date: Mon, 13 Apr 2015 16:36:23 +0200 Message-ID: <20150413143623.GP6186@cbox> References: <1427814488-28467-1-git-send-email-alex.bennee@linaro.org> <1427814488-28467-6-git-send-email-alex.bennee@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, marc.zyngier@arm.com, peter.maydell@linaro.org, agraf@suse.de, drjones@redhat.com, pbonzini@redhat.com, zhichao.huang@linaro.org, jan.kiszka@siemens.com, dahi@linux.vnet.ibm.com, r65777@freescale.com, bp@suse.de, Gleb Natapov , Russell King , Catalin Marinas , Will Deacon , Andre Przywara , Lorenzo Pieralisi , open list To: Alex =?iso-8859-1?Q?Benn=E9e?= Return-path: Content-Disposition: inline In-Reply-To: <1427814488-28467-6-git-send-email-alex.bennee@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, Mar 31, 2015 at 04:08:03PM +0100, Alex Benn=E9e wrote: > This is a precursor for later patches which will need to do more to > setup debug state before entering the hyp.S switch code. The existing > functionality for setting mdcr_el2 has been moved out of hyp.S and no= w > uses the value kept in vcpu->arch.mdcr_el2. >=20 > This also moves the conditional setting of the TDA bit from the hyp c= ode > into the C code. >=20 > Signed-off-by: Alex Benn=E9e >=20 > create mode 100644 arch/arm64/kvm/debug.c >=20 > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/k= vm_host.h > index 41008cd..8c01c97 100644 > --- a/arch/arm/include/asm/kvm_host.h > +++ b/arch/arm/include/asm/kvm_host.h > @@ -242,5 +242,7 @@ static inline void kvm_arch_hardware_unsetup(void= ) {} > static inline void kvm_arch_sync_events(struct kvm *kvm) {} > static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {} > static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)= {} > +static inline void kvm_arch_setup_debug(struct kvm_vcpu *vcpu) {} > +static inline void kvm_arch_clear_debug(struct kvm_vcpu *vcpu) {} > =20 > #endif /* __ARM_KVM_HOST_H__ */ > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index 445933d..7ea8b0e 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -523,6 +523,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu= , struct kvm_run *run) > =20 > kvm_vgic_flush_hwstate(vcpu); > kvm_timer_flush_hwstate(vcpu); > + kvm_arch_setup_debug(vcpu); > =20 > local_irq_disable(); > =20 > @@ -569,6 +570,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu= , struct kvm_run *run) > * Back from guest > *************************************************************/ > =20 > + kvm_arch_clear_debug(vcpu); > kvm_timer_sync_hwstate(vcpu); > kvm_vgic_sync_hwstate(vcpu); > =20 > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/a= sm/kvm_host.h > index 8ac3c70..0631840 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -101,6 +101,7 @@ struct kvm_vcpu_arch { > =20 > /* HYP configuration */ > u64 hcr_el2; > + u32 mdcr_el2; > =20 > /* Exception Information */ > struct kvm_vcpu_fault_info fault; > @@ -257,4 +258,7 @@ static inline void kvm_arch_sync_events(struct kv= m *kvm) {} > static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {} > static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)= {} > =20 > +void kvm_arch_setup_debug(struct kvm_vcpu *vcpu); > +void kvm_arch_clear_debug(struct kvm_vcpu *vcpu); > + > #endif /* __ARM64_KVM_HOST_H__ */ > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-= offsets.c > index f7fa65d..cd06209 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -122,6 +122,7 @@ int main(void) > DEFINE(VCPU_HPFAR_EL2, offsetof(struct kvm_vcpu, arch.fault.hpfar_= el2)); > DEFINE(VCPU_DEBUG_FLAGS, offsetof(struct kvm_vcpu, arch.debug_flag= s)); > DEFINE(VCPU_HCR_EL2, offsetof(struct kvm_vcpu, arch.hcr_el2)); > + DEFINE(VCPU_MDCR_EL2, offsetof(struct kvm_vcpu, arch.mdcr_el2)); > DEFINE(VCPU_IRQ_LINES, offsetof(struct kvm_vcpu, arch.irq_lines)); > DEFINE(VCPU_HOST_CONTEXT, offsetof(struct kvm_vcpu, arch.host_cpu_= context)); > DEFINE(VCPU_TIMER_CNTV_CTL, offsetof(struct kvm_vcpu, arch.timer_c= pu.cntv_ctl)); > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile > index 4e6e09e..6796d4a 100644 > --- a/arch/arm64/kvm/Makefile > +++ b/arch/arm64/kvm/Makefile > @@ -17,7 +17,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) +=3D $(ARM)/psci.o $(ARM= )/perf.o > =20 > kvm-$(CONFIG_KVM_ARM_HOST) +=3D emulate.o inject_fault.o regmap.o > kvm-$(CONFIG_KVM_ARM_HOST) +=3D hyp.o hyp-init.o handle_exit.o > -kvm-$(CONFIG_KVM_ARM_HOST) +=3D guest.o reset.o sys_regs.o sys_regs_= generic_v8.o > +kvm-$(CONFIG_KVM_ARM_HOST) +=3D guest.o debug.o reset.o sys_regs.o s= ys_regs_generic_v8.o > =20 > kvm-$(CONFIG_KVM_ARM_VGIC) +=3D $(KVM)/arm/vgic.o > kvm-$(CONFIG_KVM_ARM_VGIC) +=3D $(KVM)/arm/vgic-v2.o > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c > new file mode 100644 > index 0000000..8a29d0b > --- /dev/null > +++ b/arch/arm64/kvm/debug.c > @@ -0,0 +1,58 @@ > +/* > + * Debug and Guest Debug support > + * > + * Copyright (C) 2015 - Linaro Ltd > + * Author: Alex Benn=E9e > + * > + * This program is free software; you can redistribute it and/or mod= ify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program. If not, see . > + */ > + > +#include > + > +#include > +#include > + > +/** > + * kvm_arch_setup_debug - set-up debug related stuff nit: I think you want "set up" when it's a verb. > + * > + * @vcpu: the vcpu pointer > + * > + * This is called before each entry in to the hypervisor to setup an= y s/in to/into/ s/setup/set up/ > + * debug related registers. Currently this just ensures we will trap > + * access to: guest accesses to: > + * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR) > + * - Debug ROM Address (MDCR_EL2_TDRA) > + * - Power down debug registers (MDCR_EL2_TDOSA) > + * > + * Additionally the hypervisor lazily saves/restores the debug > + * register state. If it is not currently doing so (arch.debug_flags= ) > + * then we also need to ensure we trap if the guest messes with them > + * so we know we need to save them. This paragraph is a little hard to make sense of. If I understand it correctly, the point is that when debugging the guest we need to make sure guest accesses to the debug registers traps? If so, I would suggest something like: Additionally, KVM only traps guest accesses to the debug registers if the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY flag on vcpu->arch.debug_flags). Since the guest must not interfere with the hardware state when debugging the guest, we must ensure that trapping is enabled whenever we are debugging the guest. > + */ > + > +void kvm_arch_setup_debug(struct kvm_vcpu *vcpu) > +{ > + vcpu->arch.mdcr_el2 |=3D (MDCR_EL2_TPM | MDCR_EL2_TPMCR); > + vcpu->arch.mdcr_el2 |=3D (MDCR_EL2_TDRA | MDCR_EL2_TDOSA); > + > + if (!vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY) > + vcpu->arch.mdcr_el2 |=3D MDCR_EL2_TDA; > + else > + vcpu->arch.mdcr_el2 &=3D ~MDCR_EL2_TDA; > + > +} > + > +void kvm_arch_clear_debug(struct kvm_vcpu *vcpu) > +{ > + /* Nothing to do yet */ > +} > diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S > index 5befd01..be92bfe1 100644 > --- a/arch/arm64/kvm/hyp.S > +++ b/arch/arm64/kvm/hyp.S > @@ -768,17 +768,8 @@ > mov x2, #(1 << 15) // Trap CP15 Cr=3D15 > msr hstr_el2, x2 > =20 > - mrs x2, mdcr_el2 > - and x2, x2, #MDCR_EL2_HPMN_MASK > - orr x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR) > - orr x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA) > - > - // Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap > - // if not dirty. > - ldr x3, [x0, #VCPU_DEBUG_FLAGS] > - tbnz x3, #KVM_ARM64_DEBUG_DIRTY_SHIFT, 1f > - orr x2, x2, #MDCR_EL2_TDA > -1: > + // Monitor Debug Config - see kvm_arch_setup_debug() > + ldr x2, [x0, #VCPU_MDCR_EL2] > msr mdcr_el2, x2 > .endm > =20 As the other reviewers noted, this is now setting the number of PMU counters accessible to 0. I'm fine with always setting mdcr_el2 from memory, but I think we need to add code in hyp-init.S to read PMCR_EL0.= N and store that in a per-cpu (not vcpu) variable and configure mdcr_el2 using that value in kvm_arch_set_debug(), but then you need to call kvm_arch_set_debug() from a non-preemptible section, which is probably = a good idea anyway. Note that I couldn't see that we are initializing MDCR_EL2 anywhere, so that should probably be a separate fix. Thanks, -Christoffer