From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH 4/7] KVM: arm64: guest debug, add SW break point support Date: Sat, 29 Nov 2014 17:21:15 +0100 Message-ID: <20141129162115.GF23653@cbox> References: <1416931805-23223-1-git-send-email-alex.bennee@linaro.org> <1416931805-23223-5-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, 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 To: Alex =?iso-8859-1?Q?Benn=E9e?= Return-path: Content-Disposition: inline In-Reply-To: <1416931805-23223-5-git-send-email-alex.bennee@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, Nov 25, 2014 at 04:10:02PM +0000, Alex Benn=E9e wrote: > This adds support for SW breakpoints inserted by userspace. >=20 > First we need to trap all BKPT exceptions in the hypervisor (ELS). Th= is > in controlled through the MDCR_EL2 register. I've added a new field t= o 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. >=20 > Once the exception arrives we triggers an exit from the main hypervis= or > loop to the hypervisor controller. The kvm_debug_exit_arch carries th= e hypervisor controller is userspace? > address of the exception. If the controller doesn't know of breakpoin= t 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 >=20 > Signed-off-by: Alex Benn=E9e >=20 > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtua= l/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 contr= ol > flags which can include the following: > =20 > - - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86] > + - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm= 64] > - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s39= 0] > - 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 =3D false; > + > /* If it's not enabled clear all flags */ > if (!(dbg->control & KVM_GUESTDBG_ENABLE)) { > vcpu->guest_debug =3D 0; > @@ -320,8 +323,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kv= m_vcpu *vcpu, > =20 > /* 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 =3D true; > } > =20 > /* Hardware assisted Break and Watch points */ > @@ -330,6 +333,20 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct k= vm_vcpu *vcpu, > return -EINVAL; > } > =20 > + /* 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 =3D MDCR_EL2_TDE; > + } else { > + kvm_info("not routing debug exceptions"); > + vcpu->arch.mdcr_el2 =3D 0; > + } > + > return 0; > } > =20 > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/a= sm/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 { > =20 > /* HYP configuration */ > u64 hcr_el2; > + u32 mdcr_el2; > =20 > /* 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_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/handle_exit.c b/arch/arm64/kvm/handle_exi= t.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, s= truct kvm_run *run) > return 1; > } > =20 > +/** > + * 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 b= y . > + * guest debugging. If user-space decides this particular break-poin= t > + * 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 *ru= n) > +{ > + run->exit_reason =3D KVM_EXIT_DEBUG; > + run->debug.arch.exit_type =3D KVM_DEBUG_EXIT_SW_BKPT; > + run->debug.arch.address =3D *vcpu_pc(vcpu); > + kvm_info("exiting from %llx\n", run->debug.arch.address); > + return 0; > +} > + > static exit_handle_fn arm_exit_handlers[] =3D { > [ESR_EL2_EC_WFI] =3D kvm_handle_wfx, > [ESR_EL2_EC_CP15_32] =3D kvm_handle_cp15_32, > @@ -85,6 +105,8 @@ static exit_handle_fn arm_exit_handlers[] =3D { > [ESR_EL2_EC_SYS64] =3D kvm_handle_sys_reg, > [ESR_EL2_EC_IABT] =3D kvm_handle_guest_abort, > [ESR_EL2_EC_DABT] =3D kvm_handle_guest_abort, > + [ESR_EL2_EC_BKPT32] =3D kvm_handle_bkpt, > + [ESR_EL2_EC_BRK64] =3D kvm_handle_bkpt, > }; > =20 > 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) > =20 > + // 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] > --=20 > 2.1.3 >=20 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