Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753495AbaLALdd (ORCPT ); Mon, 1 Dec 2014 06:33:33 -0500 Received: from static.88-198-71-155.clients.your-server.de ([88.198.71.155]:59179 "EHLO socrates.bennee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753131AbaLALdb (ORCPT ); Mon, 1 Dec 2014 06:33:31 -0500 References: <1416931805-23223-1-git-send-email-alex.bennee@linaro.org> <1416931805-23223-5-git-send-email-alex.bennee@linaro.org> <20141129162115.GF23653@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, jan.kiszka@siemens.com, dahi@linux.vnet.ibm.com, r65777@freescale.com, bp@suse.de, pbonzini@redhat.com, Gleb Natapov , Jonathan Corbet , Russell King , Catalin Marinas , Will Deacon , Lorenzo Pieralisi , "open list\:DOCUMENTATION" , open list Subject: Re: [PATCH 4/7] KVM: arm64: guest debug, add SW break point support In-reply-to: <20141129162115.GF23653@cbox> Date: Mon, 01 Dec 2014 11:33:30 +0000 Message-ID: <87sigz1u5x.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, Nov 25, 2014 at 04:10:02PM +0000, Alex Bennée wrote: >> This adds support for SW breakpoints inserted by userspace. >> >> First we need to trap all BKPT exceptions in the hypervisor (ELS). This >> in controlled through the MDCR_EL2 register. I've added a new field to > > this is ? > >> the vcpu structure to hold this value. There should be scope to >> rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT >> manipulation in later patches. > > I don't understand what you mean with rationalising something in later > patches. I was pointing to potential future improvements. I'm wary of touching the lazy register syncing code in this patch set as it greatly increases the scope of testing. However I guess I'll have to bite the bullet and merge it in a sensible way. > >> >> Once the exception arrives we triggers an exit from the main hypervisor >> loop to the hypervisor controller. The kvm_debug_exit_arch carries the > > hypervisor controller is userspace? Yeah sorry that one sneaked through. > >> address of the exception. If the controller doesn't know of breakpoint > > the breakint ? > >> then we have a guest inserted breakpoint and the hypervisor needs to >> start again and deliver the exception to guest. > > to the guest > >> >> Signed-off-by: Alex Bennée >> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt >> index 2c6386e..9383359 100644 >> --- a/Documentation/virtual/kvm/api.txt >> +++ b/Documentation/virtual/kvm/api.txt >> @@ -2592,7 +2592,7 @@ when running. Common control bits are: >> The top 16 bits of the control field are architecture specific control >> flags which can include the following: >> >> - - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86] >> + - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64] >> - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390] >> - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86] >> - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86] >> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c >> index a0ff410..48d26bb 100644 >> --- a/arch/arm/kvm/arm.c >> +++ b/arch/arm/kvm/arm.c >> @@ -303,6 +303,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) >> int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, >> struct kvm_guest_debug *dbg) >> { >> + /* Route debug traps to el2? */ >> + bool route_el2 = false; >> + >> /* If it's not enabled clear all flags */ >> if (!(dbg->control & KVM_GUESTDBG_ENABLE)) { >> vcpu->guest_debug = 0; >> @@ -320,8 +323,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, >> >> /* Software Break Points */ >> if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) { >> - kvm_info("SW BP support requested, not yet implemented\n"); >> - return -EINVAL; >> + kvm_info("SW BP support requested\n"); >> + route_el2 = true; >> } >> >> /* Hardware assisted Break and Watch points */ >> @@ -330,6 +333,20 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, >> return -EINVAL; >> } >> >> + /* If we are going to handle any debug exceptions we need to > > wings on the comments > >> + * set MDCE_EL2.TDE to ensure they are routed to the >> + * hypervisor. If userspace determines the exception was >> + * actually internal to the guest it needs to handle >> + * re-injecting the exception. >> + */ >> + if (route_el2) { >> + kvm_info("routing debug exceptions"); >> + vcpu->arch.mdcr_el2 = MDCR_EL2_TDE; >> + } else { >> + kvm_info("not routing debug exceptions"); >> + vcpu->arch.mdcr_el2 = 0; >> + } >> + >> return 0; >> } >> >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >> index 2012c4b..38b0f07 100644 >> --- a/arch/arm64/include/asm/kvm_host.h >> +++ b/arch/arm64/include/asm/kvm_host.h >> @@ -98,6 +98,7 @@ struct kvm_vcpu_arch { >> >> /* HYP configuration */ >> u64 hcr_el2; >> + u32 mdcr_el2; >> >> /* Exception Information */ >> struct kvm_vcpu_fault_info fault; >> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c >> index 9a9fce0..8da1043 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/handle_exit.c b/arch/arm64/kvm/handle_exit.c >> index 34b8bd0..28dc92b 100644 >> --- a/arch/arm64/kvm/handle_exit.c >> +++ b/arch/arm64/kvm/handle_exit.c >> @@ -71,6 +71,26 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run) >> return 1; >> } >> >> +/** >> + * kvm_handle_bkpt - handle a break-point instruction >> + * >> + * @vcpu: the vcpu pointer >> + * >> + * By definition if we arrive here it's because we are routing >> + * all SW breakpoints to the hyper-visor as some may be a result of > > s/hyper-visor/hypervisor/ > > this sentence is weird. I think what you want is a full stop after > hypervisor and then a new sentence: Userspace may decide that this > particular breakpoint should be routed to the guest (if the breakpoint > does not come form userspace but by someone debugging a process inside > the guest), and in that case inject a software breakpoint instruction by > . > > > >> + * guest debugging. If user-space decides this particular break-point >> + * isn't for the host to handle it can re-feed the exception to the >> + * guest. >> + */ >> +static int kvm_handle_bkpt(struct kvm_vcpu *vcpu, struct kvm_run *run) >> +{ >> + run->exit_reason = KVM_EXIT_DEBUG; >> + run->debug.arch.exit_type = KVM_DEBUG_EXIT_SW_BKPT; >> + run->debug.arch.address = *vcpu_pc(vcpu); >> + kvm_info("exiting from %llx\n", run->debug.arch.address); >> + return 0; >> +} >> + >> static exit_handle_fn arm_exit_handlers[] = { >> [ESR_EL2_EC_WFI] = kvm_handle_wfx, >> [ESR_EL2_EC_CP15_32] = kvm_handle_cp15_32, >> @@ -85,6 +105,8 @@ static exit_handle_fn arm_exit_handlers[] = { >> [ESR_EL2_EC_SYS64] = kvm_handle_sys_reg, >> [ESR_EL2_EC_IABT] = kvm_handle_guest_abort, >> [ESR_EL2_EC_DABT] = kvm_handle_guest_abort, >> + [ESR_EL2_EC_BKPT32] = kvm_handle_bkpt, >> + [ESR_EL2_EC_BRK64] = kvm_handle_bkpt, >> }; >> >> static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu) >> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S >> index b72aa9f..3c733ea 100644 >> --- a/arch/arm64/kvm/hyp.S >> +++ b/arch/arm64/kvm/hyp.S >> @@ -772,6 +772,10 @@ >> orr x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR) >> orr x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA) >> >> + // Any other bits (currently TDE) >> + ldr x3, [x0, #VCPU_MDCR_EL2] >> + orr x2, x2, x3 >> + >> // Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap >> // if not dirty. >> ldr x3, [x0, #VCPU_DEBUG_FLAGS] >> -- >> 2.1.3 >> > > It may be simpler to just load/restore the MDCR_EL2 and do all > bit-manipulations for a specific VCPU in C-code instead of this. > > -Christoffer -- Alex Bennée -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/