From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Jones Subject: Re: [PATCH v2 08/10] KVM: arm64: guest debug, HW assisted debug support Date: Fri, 10 Apr 2015 14:25:21 +0200 Message-ID: <20150410122520.GA3227@hawk.usersys.redhat.com> References: <1427814488-28467-1-git-send-email-alex.bennee@linaro.org> <1427814488-28467-9-git-send-email-alex.bennee@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <1427814488-28467-9-git-send-email-alex.bennee@linaro.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Alex =?iso-8859-1?Q?Benn=E9e?= Cc: kvm@vger.kernel.org, "open list:DOCUMENTATION" , jan.kiszka@siemens.com, Will Deacon , kvmarm@lists.cs.columbia.edu, Lorenzo Pieralisi , Russell King , Jonathan Corbet , AKASHI Takahiro , zhichao.huang@linaro.org, Catalin Marinas , bp@suse.de, Gleb Natapov , marc.zyngier@arm.com, r65777@freescale.com, linux-arm-kernel@lists.infradead.org, "open list:ABI/API" , open list , dahi@linux.vnet.ibm.com, pbonzini@redhat.com List-Id: linux-api@vger.kernel.org On Tue, Mar 31, 2015 at 04:08:06PM +0100, Alex Benn=E9e wrote: > This adds support for userspace to control the HW debug registers for > guest debug. We'll only copy the $ARCH defined number across as that is > all that hyp.S will use anyway. I've moved some helper functions into > the hw_breakpoint.h header for re-use. > = > As with single step we need to tweak the guest registers to enable the > exceptions so we need to save and restore those bits. > = > Two new capabilities have been added to the KVM_EXTENSION ioctl to allow > userspace to query the number of hardware break and watch points > available on the host hardware. > = > As QEMU tests for watchpoints based on the address and not the PC we > also need to export the value of far_el2 to userspace. > = > Signed-off-by: Alex Benn=E9e > = > --- > v2 > - switched to C setup > - replace host debug registers directly into context > - minor tweak to api docs > - setup right register for debug > - add FAR_EL2 to debug exit structure > - add support fro trapping debug register access > = > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kv= m/api.txt > index 17d4f9c..ac34093 100644 > --- a/Documentation/virtual/kvm/api.txt > +++ b/Documentation/virtual/kvm/api.txt > @@ -2627,7 +2627,7 @@ The top 16 bits of the control field are architectu= re specific control > flags which can include the following: > = > - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64] > - - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390] > + - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, a= rm64] > - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86] > - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86] > - KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390] > @@ -2642,6 +2642,10 @@ updated to the correct (supplied) values. > The second part of the structure is architecture specific and > typically contains a set of debug registers. > = > +For arm64 the number of debug registers is implementation defined and > +can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and > +KVM_CAP_GUEST_DEBUG_HW_WPS capabilities. > + > When debug events exit the main run loop with the reason > KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run > structure containing architecture specific debug information. > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index c1ed8cb..a286026 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -306,6 +306,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) > = > #define KVM_GUESTDBG_VALID (KVM_GUESTDBG_ENABLE | \ > KVM_GUESTDBG_USE_SW_BP | \ > + KVM_GUESTDBG_USE_HW_BP | \ > KVM_GUESTDBG_SINGLESTEP) > = > /** > @@ -328,6 +329,26 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_v= cpu *vcpu, > return -EINVAL; > = > vcpu->guest_debug =3D dbg->control; > + > + /* Hardware assisted Break and Watch points */ > + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) { > + int nb =3D get_num_brps(); > + int nw =3D get_num_wrps(); > + > + /* Copy across up to IMPDEF debug registers to our > + * shadow copy in the vcpu structure. The debug code > + * will then set them up before we re-enter the guest. > + */ Is it necessary to limit the number copied here by anything other than what the struct supports? Userspace gave us a struct kvm_guest_debug_arch, so let's save the whole thing. How about just vcpu->arch.guest_debug_regs =3D *dbg; > + memcpy(vcpu->arch.guest_debug_regs.dbg_bcr, > + dbg->arch.dbg_bcr, sizeof(__u64)*nb); > + memcpy(vcpu->arch.guest_debug_regs.dbg_bvr, > + dbg->arch.dbg_bvr, sizeof(__u64)*nb); > + memcpy(vcpu->arch.guest_debug_regs.dbg_wcr, > + dbg->arch.dbg_wcr, sizeof(__u64)*nw); > + memcpy(vcpu->arch.guest_debug_regs.dbg_wvr, > + dbg->arch.dbg_wvr, sizeof(__u64)*nw); > + } > + > } else { > /* If not enabled clear all flags */ > vcpu->guest_debug =3D 0; > diff --git a/arch/arm64/include/asm/hw_breakpoint.h b/arch/arm64/include/= asm/hw_breakpoint.h > index 52b484b..c450552 100644 > --- a/arch/arm64/include/asm/hw_breakpoint.h > +++ b/arch/arm64/include/asm/hw_breakpoint.h > @@ -130,6 +130,18 @@ static inline void ptrace_hw_copy_thread(struct task= _struct *task) > } > #endif > = > +/* Determine number of BRP registers available. */ > +static inline int get_num_brps(void) > +{ > + return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1; > +} > + > +/* Determine number of WRP registers available. */ > +static inline int get_num_wrps(void) > +{ > + return ((read_cpuid(ID_AA64DFR0_EL1) >> 20) & 0xf) + 1; > +} > + > extern struct pmu perf_ops_bp; > = > #endif /* __KERNEL__ */ > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/k= vm_host.h > index 6a33647..2c359c9 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -106,8 +106,9 @@ struct kvm_vcpu_arch { > /* Exception Information */ > struct kvm_vcpu_fault_info fault; > = > - /* Debug state */ > + /* Guest debug state */ > u64 debug_flags; > + struct kvm_guest_debug_arch guest_debug_regs; > = > /* Pointer to host CPU context */ > kvm_cpu_context_t *host_cpu_context; > @@ -126,6 +127,7 @@ struct kvm_vcpu_arch { > u32 pstate_ss_bit; > u32 mdscr_el1_bits; > = > + struct kvm_guest_debug_arch debug_regs; > } debug_saved_regs; > = > /* Don't run the guest */ > diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/= asm/kvm.h > index 6ee70a0..73f21e4 100644 > --- a/arch/arm64/include/uapi/asm/kvm.h > +++ b/arch/arm64/include/uapi/asm/kvm.h > @@ -118,6 +118,7 @@ struct kvm_guest_debug_arch { > struct kvm_debug_exit_arch { > __u64 pc; > __u32 hsr; > + __u64 far; /* used for watchpoints */ > }; > = > struct kvm_sync_regs { > diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_bre= akpoint.c > index 98bbe06..923be44 100644 > --- a/arch/arm64/kernel/hw_breakpoint.c > +++ b/arch/arm64/kernel/hw_breakpoint.c > @@ -49,18 +49,6 @@ static DEFINE_PER_CPU(int, stepping_kernel_bp); > static int core_num_brps; > static int core_num_wrps; > = > -/* Determine number of BRP registers available. */ > -static int get_num_brps(void) > -{ > - return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1; > -} > - > -/* Determine number of WRP registers available. */ > -static int get_num_wrps(void) > -{ > - return ((read_cpuid(ID_AA64DFR0_EL1) >> 20) & 0xf) + 1; > -} > - > int hw_breakpoint_slots(int type) > { > /* > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c > index b32362c..3b368f3 100644 > --- a/arch/arm64/kvm/debug.c > +++ b/arch/arm64/kvm/debug.c > @@ -50,14 +50,19 @@ > = > void kvm_arch_setup_debug(struct kvm_vcpu *vcpu) > { > + bool trap_debug =3D false; > + > vcpu->arch.mdcr_el2 |=3D (MDCR_EL2_TPM | MDCR_EL2_TPMCR); > vcpu->arch.mdcr_el2 |=3D (MDCR_EL2_TDRA | MDCR_EL2_TDOSA); > = > - /* Trap debug register access? */ > + trace_kvm_arch_setup_debug_reg32("MDCR_EL2", vcpu->arch.mdcr_el2); This is 2 patches too early. You don't introduce this tracepoint until later. > + > + /* > + * If we are not treating debug registers are dirty we need ^^ as > + * to trap if the guest starts accessing them. > + */ > 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; > + trap_debug =3D true; How about just bool trap_debug =3D !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY); at the top instead? > = > /* Is Guest debugging in effect? */ > if (vcpu->guest_debug) { > @@ -84,10 +89,69 @@ void kvm_arch_setup_debug(struct kvm_vcpu *vcpu) > vcpu_sys_reg(vcpu, MDSCR_EL1) &=3D ~DBG_MDSCR_SS; > } > = > + /* > + * HW Break/Watch points > + */ > + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) { > + int nb =3D get_num_brps(); > + int nw =3D get_num_wrps(); > + struct kvm_guest_debug_arch *saved, *host; > + > + vcpu_sys_reg(vcpu, MDSCR_EL1) |=3D > + (DBG_MDSCR_KDE|DBG_MDSCR_MDE); > + > + /* > + * First we need to make a copy of the guest > + * debug registers before we wipe them out > + * with the ones we want to use. > + */ > + saved =3D &vcpu_debug_saved_reg(vcpu, debug_regs); > + host =3D &vcpu->arch.guest_debug_regs; Again, I don't think we need to be so precise with our copy. We can always copy extra without problems. It's just what we use that matters. And how about a couple helpers? debug_regs_save_to(struct kvm_vcpu *vcpu, struct kvm_guest_debug_arch *dst) { memcpy(dst->dbg_bcr, &vcpu_sys_reg(vcpu, DBGBCR0_EL1), sizeof(u64)*KVM_AR= M_NDBG_REGS); memcpy(dst->dbg_bvr, &vcpu_sys_reg(vcpu, DBGBVR0_EL1), sizeof(u64)*KVM_AR= M_NDBG_REGS); memcpy(dst->dbg_wcr, &vcpu_sys_reg(vcpu, DBGWCR0_EL1), sizeof(u64)*KVM_AR= M_NDBG_REGS); memcpy(dst->dbg_wvr, &vcpu_sys_reg(vcpu, DBGWVR0_EL1), sizeof(u64)*KVM_AR= M_NDBG_REGS); } debug_regs_restore_from(struct kvm_vcpu *vcpu, struct kvm_guest_debug_arch = *src) { memcpy(&vcpu_sys_reg(vcpu, DBGBCR0_EL1), src->dbg_bcr, sizeof(u64)*KVM_AR= M_NDBG_REGS); memcpy(&vcpu_sys_reg(vcpu, DBGBVR0_EL1), src->dbg_bvr, sizeof(u64)*KVM_AR= M_NDBG_REGS); memcpy(&vcpu_sys_reg(vcpu, DBGWCR0_EL1), src->dbg_wcr, sizeof(u64)*KVM_AR= M_NDBG_REGS); memcpy(&vcpu_sys_reg(vcpu, DBGWVR0_EL1), src->dbg_wvr, sizeof(u64)*KVM_AR= M_NDBG_REGS); } > + > + /* Save guest values */ > + memcpy(&saved->dbg_bcr, > + &vcpu_sys_reg(vcpu, DBGBCR0_EL1), > + sizeof(__u64)*nb); > + memcpy(&saved->dbg_bvr, > + &vcpu_sys_reg(vcpu, DBGBVR0_EL1), > + sizeof(__u64)*nb); > + memcpy(&saved->dbg_wcr, > + &vcpu_sys_reg(vcpu, DBGWCR0_EL1), > + sizeof(__u64)*nw); > + memcpy(&saved->dbg_wvr, > + &vcpu_sys_reg(vcpu, DBGWVR0_EL1), > + sizeof(__u64)*nw); > + > + /* Copy in host values */ > + memcpy(&vcpu_sys_reg(vcpu, DBGBCR0_EL1), > + &host->dbg_bcr, > + sizeof(__u64)*nb); > + memcpy(&vcpu_sys_reg(vcpu, DBGBVR0_EL1), > + &host->dbg_bvr, > + sizeof(__u64)*nb); > + memcpy(&vcpu_sys_reg(vcpu, DBGWCR0_EL1), > + &host->dbg_wcr, > + sizeof(__u64)*nw); > + memcpy(&vcpu_sys_reg(vcpu, DBGWVR0_EL1), > + &host->dbg_wvr, > + sizeof(__u64)*nw); > + > + /* Make sure hyp.S copies them in/out */ > + vcpu->arch.debug_flags |=3D KVM_ARM64_DEBUG_DIRTY; > + /* Also track guest changes */ > + trap_debug =3D true; > + } > + > } else { > /* Debug operations can go straight to the guest */ > vcpu->arch.mdcr_el2 &=3D ~MDCR_EL2_TDE; > } > + > + /* Trap debug register access? */ > + if (trap_debug) > + 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) > @@ -100,5 +164,31 @@ void kvm_arch_clear_debug(struct kvm_vcpu *vcpu) > vcpu_sys_reg(vcpu, MDSCR_EL1) &=3D ~MDSCR_EL1_DEBUG_BITS; > vcpu_sys_reg(vcpu, MDSCR_EL1) |=3D > vcpu_debug_saved_reg(vcpu, mdscr_el1_bits); > + > + /* > + * If we were using HW debug we need to restore the > + * values the guest had set them up with > + */ > + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) { > + struct kvm_guest_debug_arch *regs; > + int nb =3D get_num_brps(); > + int nw =3D get_num_wrps(); > + > + regs =3D &vcpu_debug_saved_reg(vcpu, debug_regs); debug_regs_restore_from(vcpu, regs); > + > + /* Restore the saved debug register values */ > + memcpy(&vcpu_sys_reg(vcpu, DBGBCR0_EL1), > + ®s->dbg_bcr, > + sizeof(__u64)*nb); > + memcpy(&vcpu_sys_reg(vcpu, DBGBVR0_EL1), > + ®s->dbg_bvr, > + sizeof(__u64)*nb); > + memcpy(&vcpu_sys_reg(vcpu, DBGWCR0_EL1), > + ®s->dbg_wcr, > + sizeof(__u64)*nw); > + memcpy(&vcpu_sys_reg(vcpu, DBGWVR0_EL1), > + ®s->dbg_wvr, > + sizeof(__u64)*nw); > + } > } > } > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > index 16accae..460a1aa 100644 > --- a/arch/arm64/kvm/handle_exit.c > +++ b/arch/arm64/kvm/handle_exit.c > @@ -101,7 +101,11 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *v= cpu, struct kvm_run *run) > run->debug.arch.hsr =3D hsr; > = > switch (hsr >> ESR_ELx_EC_SHIFT) { > + case ESR_ELx_EC_WATCHPT_LOW: > + run->debug.arch.far =3D vcpu->arch.fault.far_el2; > + /* fall through */ > case ESR_ELx_EC_SOFTSTP_LOW: > + case ESR_ELx_EC_BREAKPT_LOW: > case ESR_ELx_EC_BKPT32: > case ESR_ELx_EC_BRK64: > run->debug.arch.pc =3D *vcpu_pc(vcpu); > @@ -129,6 +133,8 @@ static exit_handle_fn arm_exit_handlers[] =3D { > [ESR_ELx_EC_IABT_LOW] =3D kvm_handle_guest_abort, > [ESR_ELx_EC_DABT_LOW] =3D kvm_handle_guest_abort, > [ESR_ELx_EC_SOFTSTP_LOW]=3D kvm_handle_guest_debug, > + [ESR_ELx_EC_WATCHPT_LOW]=3D kvm_handle_guest_debug, > + [ESR_ELx_EC_BREAKPT_LOW]=3D kvm_handle_guest_debug, > [ESR_ELx_EC_BKPT32] =3D kvm_handle_guest_debug, > [ESR_ELx_EC_BRK64] =3D kvm_handle_guest_debug, > }; > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c > index 0b43265..c2732c7 100644 > --- a/arch/arm64/kvm/reset.c > +++ b/arch/arm64/kvm/reset.c > @@ -64,6 +64,12 @@ int kvm_arch_dev_ioctl_check_extension(long ext) > case KVM_CAP_ARM_EL1_32BIT: > r =3D cpu_has_32bit_el1(); > break; > + case KVM_CAP_GUEST_DEBUG_HW_BPS: > + r =3D get_num_brps(); > + break; > + case KVM_CAP_GUEST_DEBUG_HW_WPS: > + r =3D get_num_wrps(); > + break; > default: > r =3D 0; > } > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index c370b40..be9b188 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -196,16 +196,49 @@ static bool trap_dbgauthstatus_el1(struct kvm_vcpu = *vcpu, > * - If the dirty bit is set, save guest registers, restore host > * registers and clear the dirty bit. This ensure that the host can > * now use the debug registers. > + * > + * We also use this mechanism to set-up the debug registers for guest setup > + * debugging. If this is the case we want to ensure the guest sees > + * the right versions of the registers - even if they are not going to > + * be effective while guest debug is using HW debug. > + * no need for this blank comment line > */ > + > static bool trap_debug_regs(struct kvm_vcpu *vcpu, > const struct sys_reg_params *p, > const struct sys_reg_desc *r) > { > - if (p->is_write) { > - vcpu_sys_reg(vcpu, r->reg) =3D *vcpu_reg(vcpu, p->Rt); > - vcpu->arch.debug_flags |=3D KVM_ARM64_DEBUG_DIRTY; > + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) { > + struct kvm_guest_debug_arch *saved; > + __u64 *val; > + > + saved =3D &vcpu_debug_saved_reg(vcpu, debug_regs); Here we don't bother enforcing num_brps/wrps, which is fine by me. > + > + if (r->reg >=3D DBGBCR0_EL1 && r->reg <=3D DBGBCR15_EL1) > + val =3D &saved->dbg_bcr[r->reg - DBGBCR0_EL1]; > + else if (r->reg >=3D DBGBVR0_EL1 && r->reg <=3D DBGBVR15_EL1) > + val =3D &saved->dbg_bvr[r->reg - DBGBVR0_EL1]; > + else if (r->reg >=3D DBGWCR0_EL1 && r->reg <=3D DBGWCR15_EL1) > + val =3D &saved->dbg_wcr[r->reg - DBGWCR0_EL1]; > + else if (r->reg >=3D DBGWVR0_EL1 && r->reg <=3D DBGWVR15_EL1) > + val =3D &saved->dbg_wvr[r->reg - DBGWVR0_EL1]; > + else { > + kvm_err("Bad register index %d\n", r->reg); > + return false; > + } > + > + if (p->is_write) > + *val =3D *vcpu_reg(vcpu, p->Rt); > + else > + *vcpu_reg(vcpu, p->Rt) =3D *val; > + > } else { > - *vcpu_reg(vcpu, p->Rt) =3D vcpu_sys_reg(vcpu, r->reg); > + if (p->is_write) { > + vcpu_sys_reg(vcpu, r->reg) =3D *vcpu_reg(vcpu, p->Rt); > + vcpu->arch.debug_flags |=3D KVM_ARM64_DEBUG_DIRTY; > + } else { > + *vcpu_reg(vcpu, p->Rt) =3D vcpu_sys_reg(vcpu, r->reg); > + } > } > = > return true; > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index ce2db14..0e48c0d 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -771,6 +771,8 @@ struct kvm_ppc_smmu_info { > #define KVM_CAP_PPC_ENABLE_HCALL 104 > #define KVM_CAP_CHECK_EXTENSION_VM 105 > #define KVM_CAP_S390_USER_SIGP 106 > +#define KVM_CAP_GUEST_DEBUG_HW_BPS 107 > +#define KVM_CAP_GUEST_DEBUG_HW_WPS 108 > = > #ifdef KVM_CAP_IRQ_ROUTING > = > -- = > 2.3.4 > =