Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932614AbbDIOQZ (ORCPT ); Thu, 9 Apr 2015 10:16:25 -0400 Received: from static.88-198-71-155.clients.your-server.de ([88.198.71.155]:59487 "EHLO socrates.bennee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751445AbbDIOQX (ORCPT ); Thu, 9 Apr 2015 10:16:23 -0400 References: <1427814488-28467-1-git-send-email-alex.bennee@linaro.org> <1427814488-28467-8-git-send-email-alex.bennee@linaro.org> <20150409132442.GE3212@hawk.usersys.redhat.com> From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Andrew Jones Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, christoffer.dall@linaro.org, marc.zyngier@arm.com, peter.maydell@linaro.org, agraf@suse.de, 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 , open list Subject: Re: [PATCH v2 07/10] KVM: arm64: guest debug, add support for single-step In-reply-to: <20150409132442.GE3212@hawk.usersys.redhat.com> Date: Thu, 09 Apr 2015 15:16:10 +0100 Message-ID: <8761951j6d.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 Content-Length: 7282 Lines: 219 Andrew Jones writes: > On Tue, Mar 31, 2015 at 04:08:05PM +0100, Alex Bennée wrote: >> This adds support for single-stepping the guest. As userspace can and >> will manipulate guest registers before restarting any tweaking of the >> registers has to occur just before control is passed back to the guest. >> Furthermore while guest debugging is in effect we need to squash the >> ability of the guest to single-step itself as we have no easy way of >> re-entering the guest after the exception has been delivered to the >> hypervisor. >> >> Signed-off-by: Alex Bennée >> >> --- >> v2 >> - Move pstate/mdscr manipulation into C >> - don't export guest_debug to assembly >> - add accessor for saved_debug regs >> - tweak save/restore of mdscr_el1 >> >> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c >> index d3bc8dc..c1ed8cb 100644 >> --- a/arch/arm/kvm/arm.c >> +++ b/arch/arm/kvm/arm.c >> @@ -304,7 +304,21 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) >> kvm_arm_set_running_vcpu(NULL); >> } >> >> -#define KVM_GUESTDBG_VALID (KVM_GUESTDBG_ENABLE|KVM_GUESTDBG_USE_SW_BP) >> +#define KVM_GUESTDBG_VALID (KVM_GUESTDBG_ENABLE | \ >> + KVM_GUESTDBG_USE_SW_BP | \ >> + KVM_GUESTDBG_SINGLESTEP) >> + >> +/** >> + * kvm_arch_vcpu_ioctl_set_guest_debug - Setup guest debugging >> + * @kvm: pointer to the KVM struct >> + * @kvm_guest_debug: the ioctl data buffer >> + * >> + * This sets up the VM for guest debugging. Care has to be taken when >> + * manipulating guest registers as these will be set/cleared by the >> + * hyper-visor controller, typically before each kvm_run event. As a >> + * result modification of the guest registers needs to take place >> + * after they have been restored in the hyp.S trampoline code. >> + */ >> >> int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, >> struct kvm_guest_debug *dbg) >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >> index 0631840..6a33647 100644 >> --- a/arch/arm64/include/asm/kvm_host.h >> +++ b/arch/arm64/include/asm/kvm_host.h >> @@ -121,6 +121,13 @@ struct kvm_vcpu_arch { >> * here. >> */ >> >> + /* Registers pre any guest debug manipulations */ >> + struct { >> + u32 pstate_ss_bit; >> + u32 mdscr_el1_bits; >> + >> + } debug_saved_regs; > > Hmm, you have a struct called "regs", but then each member is > suffixed with _bit(s). This looks awkward. Later on mdscr gets expanded and properly shadowed but your right the pstate_ss_bit is a bit of a fiddle. I'll see if there is a neater way. > > >> + >> /* Don't run the guest */ >> bool pause; >> >> @@ -143,6 +150,7 @@ struct kvm_vcpu_arch { >> >> #define vcpu_gp_regs(v) (&(v)->arch.ctxt.gp_regs) >> #define vcpu_sys_reg(v,r) ((v)->arch.ctxt.sys_regs[(r)]) >> +#define vcpu_debug_saved_reg(v, r) ((v)->arch.debug_saved_regs.r) >> /* >> * CP14 and CP15 live in the same array, as they are backed by the >> * same system registers. >> diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c >> index cff0475..b32362c 100644 >> --- a/arch/arm64/kvm/debug.c >> +++ b/arch/arm64/kvm/debug.c >> @@ -19,8 +19,16 @@ >> >> #include >> >> +#include >> +#include >> #include >> #include >> +#include >> + >> +/* These are the bits of MDSCR_EL1 we may mess with */ >> +#define MDSCR_EL1_DEBUG_BITS (DBG_MDSCR_SS | \ >> + DBG_MDSCR_KDE | \ >> + DBG_MDSCR_MDE) > > _MASK instead of _BITS ? > >> >> /** >> * kvm_arch_setup_debug - set-up debug related stuff >> @@ -51,15 +59,46 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu) >> else >> vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDA; >> >> - /* Trap breakpoints? */ >> - if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) >> + /* Is Guest debugging in effect? */ >> + if (vcpu->guest_debug) { >> vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE; >> - else >> - vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE; >> >> + /* Save pstate/mdscr */ >> + vcpu_debug_saved_reg(vcpu, pstate_ss_bit) = >> + *vcpu_cpsr(vcpu) & DBG_SPSR_SS; >> + vcpu_debug_saved_reg(vcpu, mdscr_el1_bits) = >> + vcpu_sys_reg(vcpu, MDSCR_EL1) & MDSCR_EL1_DEBUG_BITS; > > I think it would be clearer if we embed the masks into helper > functions, and, assuming we drop the _bits concept too, then > > #define SPSR_DEBUG_MASK DBG_SPSR_SS > > vcpu_debug_save_regs(vcpu) > { > vcpu->arch.debug_saved_regs.pstate = *vcpu_cpsr(vcpu); > vcpu->arch.debug_saved_regs.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1); > } > > vcpu_debug_restore_regs(vcpu) > { > *vcpu_cpsr(vcpu) |= > (vcpu->arch.debug_saved_regs.pstate & SPSR_DEBUG_MASK); > vcpu_sys_reg(vcpu, MDSCR_EL1) |= > (vcpu->arch.debug_saved_regs.mdscr_el1 & MDSCR_EL1_DEBUG_MASK) > } Makes sense > >> + /* >> + * Single Step (ARM ARM D2.12.3 The software step state >> + * machine) >> + * >> + * If we are doing Single Step we need to manipulate >> + * MDSCR_EL1.SS and PSTATE.SS. If not we need to >> + * suppress the guest from messing with it. >> + */ >> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) { >> + *vcpu_cpsr(vcpu) |= DBG_SPSR_SS; >> + vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS; >> + } else { >> + *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; >> + vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS; >> + } >> + >> + } else { >> + /* Debug operations can go straight to the guest */ >> + vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE; >> + } >> } >> >> void kvm_arch_clear_debug(struct kvm_vcpu *vcpu) >> { >> - /* Nothing to do yet */ > > This would now just be > > if (vcpu->guest_debug) > vcpu_debug_restore_regs(vcpu); > >> + if (vcpu->guest_debug) { >> + /* Restore pstate/mdscr bits we may have messed with */ >> + *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS; >> + *vcpu_cpsr(vcpu) |= vcpu_debug_saved_reg(vcpu, pstate_ss_bit); >> + >> + vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~MDSCR_EL1_DEBUG_BITS; >> + vcpu_sys_reg(vcpu, MDSCR_EL1) |= >> + vcpu_debug_saved_reg(vcpu, mdscr_el1_bits); >> + } >> } >> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c >> index ed1bbb4..16accae 100644 >> --- a/arch/arm64/kvm/handle_exit.c >> +++ b/arch/arm64/kvm/handle_exit.c >> @@ -101,6 +101,7 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run) >> run->debug.arch.hsr = hsr; >> >> switch (hsr >> ESR_ELx_EC_SHIFT) { >> + case ESR_ELx_EC_SOFTSTP_LOW: >> case ESR_ELx_EC_BKPT32: >> case ESR_ELx_EC_BRK64: >> run->debug.arch.pc = *vcpu_pc(vcpu); >> @@ -127,6 +128,7 @@ static exit_handle_fn arm_exit_handlers[] = { >> [ESR_ELx_EC_SYS64] = kvm_handle_sys_reg, >> [ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort, >> [ESR_ELx_EC_DABT_LOW] = kvm_handle_guest_abort, >> + [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug, >> [ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug, >> [ESR_ELx_EC_BRK64] = kvm_handle_guest_debug, >> }; >> -- >> 2.3.4 >> -- 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/