From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932381AbbDMP34 (ORCPT ); Mon, 13 Apr 2015 11:29:56 -0400 Received: from static.88-198-71-155.clients.your-server.de ([88.198.71.155]:57816 "EHLO socrates.bennee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932101AbbDMP3y (ORCPT ); Mon, 13 Apr 2015 11:29:54 -0400 References: <1427814488-28467-1-git-send-email-alex.bennee@linaro.org> <1427814488-28467-6-git-send-email-alex.bennee@linaro.org> <20150413143623.GP6186@cbox> From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Christoffer Dall 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 Subject: Re: [PATCH v2 05/10] KVM: arm: introduce kvm_arch_setup/clear_debug() In-reply-to: <20150413143623.GP6186@cbox> Date: Mon, 13 Apr 2015 16:29:53 +0100 Message-ID: <87zj6cjbbi.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 127.0.0.1 X-SA-Exim-Mail-From: alex.bennee@linaro.org X-SA-Exim-Scanned: No (on socrates.bennee.com); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christoffer Dall writes: > On Tue, Mar 31, 2015 at 04:08:03PM +0100, Alex Bennée 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 now >> uses the value kept in vcpu->arch.mdcr_el2. >> >> This also moves the conditional setting of the TDA bit from the hyp code >> into the C code. >> >> Signed-off-by: Alex Bennée >> >> create mode 100644 arch/arm64/kvm/debug.c >> >> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_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) {} >> >> #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) >> >> kvm_vgic_flush_hwstate(vcpu); >> kvm_timer_flush_hwstate(vcpu); >> + kvm_arch_setup_debug(vcpu); >> >> local_irq_disable(); >> >> @@ -569,6 +570,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) >> * Back from guest >> *************************************************************/ >> >> + kvm_arch_clear_debug(vcpu); >> kvm_timer_sync_hwstate(vcpu); >> kvm_vgic_sync_hwstate(vcpu); >> >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/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 { >> >> /* HYP configuration */ >> u64 hcr_el2; >> + u32 mdcr_el2; >> >> /* Exception Information */ >> struct kvm_vcpu_fault_info fault; >> @@ -257,4 +258,7 @@ 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) {} >> >> +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_flags)); >> 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_cpu.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) += $(ARM)/psci.o $(ARM)/perf.o >> >> kvm-$(CONFIG_KVM_ARM_HOST) += emulate.o inject_fault.o regmap.o >> kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o >> -kvm-$(CONFIG_KVM_ARM_HOST) += guest.o reset.o sys_regs.o sys_regs_generic_v8.o >> +kvm-$(CONFIG_KVM_ARM_HOST) += guest.o debug.o reset.o sys_regs.o sys_regs_generic_v8.o >> >> kvm-$(CONFIG_KVM_ARM_VGIC) += $(KVM)/arm/vgic.o >> kvm-$(CONFIG_KVM_ARM_VGIC) += $(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 Bennée >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * 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 any > > 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 |= (MDCR_EL2_TPM | MDCR_EL2_TPMCR); >> + vcpu->arch.mdcr_el2 |= (MDCR_EL2_TDRA | MDCR_EL2_TDOSA); >> + >> + if (!vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY) >> + vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA; >> + else >> + vcpu->arch.mdcr_el2 &= ~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=15 >> msr hstr_el2, x2 >> >> - 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 >> > > 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. Yeah because I couldn't see it being set I figured it was OK to blat it with zeros. But you are right we should set it up properly if we are going to mess with it. > > Thanks, > -Christoffer -- Alex Bennée