On 10.05.2013, at 19:31, Bhushan Bharat-R65777 wrote: > > >> -----Original Message----- >> From: Alexander Graf [mailto:agraf@xxxxxxx] >> Sent: Friday, May 10, 2013 3:48 PM >> To: Bhushan Bharat-R65777 >> Cc: kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Wood Scott-B07421; >> tiejun.chen@xxxxxxxxxxxxx; Bhushan Bharat-R65777 >> Subject: Re: [PATCH] KVM: PPC: Add userspace debug stub support >> >> >> On 07.05.2013, at 11:40, Bharat Bhushan wrote: >> >>> This patch adds the debug stub support on booke/bookehv. >>> Now QEMU debug stub can use hw breakpoint, watchpoint and software >>> breakpoint to debug guest. >>> >>> This is how we save/restore debug register context when switching >>> between guest, userspace and kernel user-process: >>> >>> When QEMU is running >>> -> thread->debug_reg == QEMU debug register context. >>> -> Kernel will handle switching the debug register on context switch. >>> -> no vcpu_load() called >>> >>> QEMU makes ioctls (except RUN) >>> -> This will call vcpu_load() >>> -> should not change context. >>> -> Some ioctls can change vcpu debug register, context saved in >>> -> vcpu->debug_regs >>> >>> QEMU Makes RUN ioctl >>> -> Save thread->debug_reg on STACK >>> -> Store thread->debug_reg == vcpu->debug_reg load thread->debug_reg >>> -> RUN VCPU ( So thread points to vcpu context ) >>> >>> Context switch happens When VCPU running >>> -> makes vcpu_load() should not load any context kernel loads the vcpu >>> -> context as thread->debug_regs points to vcpu context. >>> >>> On heavyweight_exit >>> -> Load the context saved on stack in thread->debug_reg >>> >>> Currently we do not support debug resource emulation to guest, On >>> debug exception, always exit to user space irrespective of user space >>> is expecting the debug exception or not. If this is unexpected >>> exception (breakpoint/watchpoint event not set by >>> userspace) then let us leave the action on user space. This is similar >>> to what it was before, only thing is that now we have proper exit >>> state available to user space. >>> >>> Signed-off-by: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx> >>> --- >>> arch/powerpc/include/asm/kvm_host.h | 3 + >>> arch/powerpc/include/uapi/asm/kvm.h | 1 + >>> arch/powerpc/kvm/booke.c | 242 ++++++++++++++++++++++++++++++++--- >>> arch/powerpc/kvm/booke.h | 5 + >>> 4 files changed, 233 insertions(+), 18 deletions(-) >>> >>> diff --git a/arch/powerpc/include/asm/kvm_host.h >>> b/arch/powerpc/include/asm/kvm_host.h >>> index 838a577..1b29945 100644 >>> --- a/arch/powerpc/include/asm/kvm_host.h >>> +++ b/arch/powerpc/include/asm/kvm_host.h >>> @@ -524,7 +524,10 @@ struct kvm_vcpu_arch { >>> u32 eptcfg; >>> u32 epr; >>> u32 crit_save; >>> + /* guest debug registers*/ >>> struct debug_reg dbg_reg; >>> + /* shadow debug registers */ >> >> Please be more verbose here. What exactly does this contain? Why do we need >> shadow and non-shadow registers? The comment as it is reads like >> >> /* Add one plus one */ >> x = 1 + 1; > > > /* > * Shadow debug registers hold the debug register content > * to be written in h/w debug register on behalf of guest > * written value or user space written value. > */ /* hardware visible debug registers when in guest state */ > > >> >>> + struct debug_reg shadow_dbg_reg; >>> #endif >>> gpa_t paddr_accessed; >>> gva_t vaddr_accessed; >>> diff --git a/arch/powerpc/include/uapi/asm/kvm.h >>> b/arch/powerpc/include/uapi/asm/kvm.h >>> index ded0607..f5077c2 100644 >>> --- a/arch/powerpc/include/uapi/asm/kvm.h >>> +++ b/arch/powerpc/include/uapi/asm/kvm.h >>> @@ -27,6 +27,7 @@ >>> #define __KVM_HAVE_PPC_SMT >>> #define __KVM_HAVE_IRQCHIP >>> #define __KVM_HAVE_IRQ_LINE >>> +#define __KVM_HAVE_GUEST_DEBUG >>> >>> struct kvm_regs { >>> __u64 pc; >>> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c index >>> ef99536..6a44ad4 100644 >>> --- a/arch/powerpc/kvm/booke.c >>> +++ b/arch/powerpc/kvm/booke.c >>> @@ -133,6 +133,29 @@ static void kvmppc_vcpu_sync_fpu(struct kvm_vcpu >>> *vcpu) #endif } >>> >>> +static void kvmppc_vcpu_sync_debug(struct kvm_vcpu *vcpu) { >>> + /* Synchronize guest's desire to get debug interrupts into shadow >>> +MSR */ #ifndef CONFIG_KVM_BOOKE_HV >>> + vcpu->arch.shadow_msr &= ~MSR_DE; >>> + vcpu->arch.shadow_msr |= vcpu->arch.shared->msr & MSR_DE; #endif >>> + >>> + /* Force enable debug interrupts when user space wants to debug */ >>> + if (vcpu->guest_debug) { >>> +#ifdef CONFIG_KVM_BOOKE_HV >>> + /* >>> + * Since there is no shadow MSR, sync MSR_DE into the guest >>> + * visible MSR. >>> + */ >>> + vcpu->arch.shared->msr |= MSR_DE; >>> +#else >>> + vcpu->arch.shadow_msr |= MSR_DE; >>> + vcpu->arch.shared->msr &= ~MSR_DE; >>> +#endif >>> + } >>> +} >>> + >>> /* >>> * Helper function for "full" MSR writes. No need to call this if >>> only >>> * EE/CE/ME/DE/RI are changing. >>> @@ -150,6 +173,7 @@ void kvmppc_set_msr(struct kvm_vcpu *vcpu, u32 new_msr) >>> kvmppc_mmu_msr_notify(vcpu, old_msr); >>> kvmppc_vcpu_sync_spe(vcpu); >>> kvmppc_vcpu_sync_fpu(vcpu); >>> + kvmppc_vcpu_sync_debug(vcpu); >>> } >>> >>> static void kvmppc_booke_queue_irqprio(struct kvm_vcpu *vcpu, @@ >>> -655,6 +679,7 @@ int kvmppc_core_check_requests(struct kvm_vcpu *vcpu) >>> int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) { >>> int ret, s; >>> + struct debug_reg debug; >>> #ifdef CONFIG_PPC_FPU >>> unsigned int fpscr; >>> int fpexc_mode; >>> @@ -699,11 +724,27 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct >> kvm_vcpu *vcpu) >>> kvmppc_load_guest_fp(vcpu); >>> #endif >>> >>> + /* >>> + * Clear current->thread.dbcr0 so that kernel does not >>> + * restore h/w registers on context switch in vcpu running state. >>> + */ >> >> Incorrect comment? > > Leftover from previous code, will remove this. > >> >>> + /* Save thread->debug context on stack */ >> >> /* Switch to guest debug context */ >> >>> + memcpy(&debug, ¤t->thread.debug, sizeof(struct debug_reg)); >> >> debug = current->thread.debug; >> >>> + /* Load vcpu debug context in thread->debug */ >>> + memcpy(¤t->thread.debug, &vcpu->arch.shadow_dbg_reg, >>> + sizeof(struct debug_reg)); >> >> current->thread.debug = vcpu->arch.shadow_dbg_reg; >> >>> + >>> + switch_booke_debug_regs(¤t->thread); >>> + >>> ret = __kvmppc_vcpu_run(kvm_run, vcpu); >>> >>> /* No need for kvm_guest_exit. It's done in handle_exit. >>> We also get here with interrupts enabled. */ >>> >>> + /* Restore userspace context in thread->dbcr0 from stack*/ >> >> /* Switch back to user space debug context */ >> >>> + memcpy(¤t->thread.debug, &debug, sizeof(struct debug_reg)); >> >> current->thread.debug = debug; >> >>> + switch_booke_debug_regs(¤t->thread); >>> + >>> #ifdef CONFIG_PPC_FPU >>> kvmppc_save_guest_fp(vcpu); >>> >>> @@ -759,6 +800,36 @@ static int emulation_exit(struct kvm_run *run, struct >> kvm_vcpu *vcpu) >>> } >>> } >>> >>> +/* >>> + * Currently we do not support debug resource emulation to guest, >>> + * so always exit to user space irrespective of user space is >>> + * expecting the debug exception or not. This is unexpected event >>> + * and let us leave the action on user space. >> >> Please rework your wording. >> >>> + */ >>> +static int kvmppc_handle_debug(struct kvm_run *run, struct kvm_vcpu >>> +*vcpu) { >>> + struct debug_reg *dbg_reg = &(vcpu->arch.shadow_dbg_reg); >>> + u32 dbsr = vcpu->arch.dbsr; >>> + >>> + run->debug.arch.status = 0; >>> + run->debug.arch.address = vcpu->arch.pc; >>> + >>> + if (dbsr & (DBSR_IAC1 | DBSR_IAC2 | DBSR_IAC3 | DBSR_IAC4)) { >>> + run->debug.arch.status |= KVMPPC_DEBUG_BREAKPOINT; >>> + } else { >>> + if (dbsr & (DBSR_DAC1W | DBSR_DAC2W)) >>> + run->debug.arch.status |= KVMPPC_DEBUG_WATCH_WRITE; >>> + else if (dbsr & (DBSR_DAC1R | DBSR_DAC2R)) >>> + run->debug.arch.status |= KVMPPC_DEBUG_WATCH_READ; >>> + if (dbsr & (DBSR_DAC1R | DBSR_DAC1W)) >>> + run->debug.arch.address = dbg_reg->dac1; >>> + else if (dbsr & (DBSR_DAC2R | DBSR_DAC2W)) >>> + run->debug.arch.address = dbg_reg->dac2; >>> + } >>> + >>> + return RESUME_HOST; >>> +} >>> + >>> static void kvmppc_fill_pt_regs(struct pt_regs *regs) { >>> ulong r1, ip, msr, lr; >>> @@ -819,6 +890,11 @@ static void kvmppc_restart_interrupt(struct kvm_vcpu >> *vcpu, >>> case BOOKE_INTERRUPT_CRITICAL: >>> unknown_exception(®s); >>> break; >>> + case BOOKE_INTERRUPT_DEBUG: >>> + /* Save DBSR before preemption is enabled */ >>> + vcpu->arch.dbsr = mfspr(SPRN_DBSR); >>> + kvmppc_clear_dbsr(); >>> + break; >>> } >>> } >>> >>> @@ -1118,18 +1194,10 @@ int kvmppc_handle_exit(struct kvm_run *run, struct >> kvm_vcpu *vcpu, >>> } >>> >>> case BOOKE_INTERRUPT_DEBUG: { >>> - u32 dbsr; >>> - >>> - vcpu->arch.pc = mfspr(SPRN_CSRR0); >>> - >>> - /* clear IAC events in DBSR register */ >>> - dbsr = mfspr(SPRN_DBSR); >>> - dbsr &= DBSR_IAC1 | DBSR_IAC2 | DBSR_IAC3 | DBSR_IAC4; >>> - mtspr(SPRN_DBSR, dbsr); >>> - >>> - run->exit_reason = KVM_EXIT_DEBUG; >>> + r = kvmppc_handle_debug(run, vcpu); >>> + if (r == RESUME_HOST) >>> + run->exit_reason = KVM_EXIT_DEBUG; >>> kvmppc_account_exit(vcpu, DEBUG_EXITS); >>> - r = RESUME_HOST; >>> break; >>> } >>> >>> @@ -1180,7 +1248,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu) >>> kvmppc_set_msr(vcpu, 0); >>> >>> #ifndef CONFIG_KVM_BOOKE_HV >>> - vcpu->arch.shadow_msr = MSR_USER | MSR_DE | MSR_IS | MSR_DS; >>> + vcpu->arch.shadow_msr = MSR_USER | MSR_IS | MSR_DS; >>> vcpu->arch.shadow_pid = 1; >>> vcpu->arch.shared->msr = 0; >>> #endif >>> @@ -1557,12 +1625,6 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, >> struct kvm_one_reg *reg) >>> return r; >>> } >>> >>> -int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, >>> - struct kvm_guest_debug *dbg) >>> -{ >>> - return -EINVAL; >>> -} >>> - >>> int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu >>> *fpu) { >>> return -ENOTSUPP; >>> @@ -1668,6 +1730,145 @@ void kvmppc_decrementer_func(unsigned long data) >>> kvmppc_set_tsr_bits(vcpu, TSR_DIS); >>> } >>> >>> +static int kvmppc_booke_set_breakpoint(struct kvm_vcpu *vcpu, >>> +uint64_t addr, >> >> s/set/add/ >> >>> + int index) >>> +{ >>> + struct debug_reg *dbg_reg = &(vcpu->arch.shadow_dbg_reg); >>> + >>> + switch (index) { >>> + case 0: >>> + dbg_reg->dbcr0 |= DBCR0_IAC1 | DBCR0_IDM; >>> + dbg_reg->iac1 = addr; >>> + break; >>> + case 1: >>> + dbg_reg->dbcr0 |= DBCR0_IAC2 | DBCR0_IDM; >>> + dbg_reg->iac2 = addr; >>> + break; >>> +#if CONFIG_PPC_ADV_DEBUG_IACS > 2 >>> + case 2: >>> + dbg_reg->dbcr0 |= DBCR0_IAC3 | DBCR0_IDM; >>> + dbg_reg->iac3 = addr; >>> + break; >>> + case 3: >>> + dbg_reg->dbcr0 |= DBCR0_IAC4 | DBCR0_IDM; >>> + dbg_reg->iac4 = addr; >>> + break; >>> +#endif >>> + default: >>> + return -EINVAL; >>> + } >> >> dbg_reg->dbcr0 |= DBCR0_IDM; >> >>> + return 0; >>> +} >>> + >>> +static int kvmppc_booke_set_watchpoint(struct kvm_vcpu *vcpu, >>> +uint64_t addr, >> >> s/set/add/ >> >>> + int type, int index) >>> +{ >>> + struct debug_reg *dbg_reg = &(vcpu->arch.shadow_dbg_reg); >>> + >>> + switch (index) { >>> + case 0: >>> + if (type & KVMPPC_DEBUG_WATCH_READ) >>> + dbg_reg->dbcr0 |= DBCR0_DAC1R | DBCR0_IDM; >>> + if (type & KVMPPC_DEBUG_WATCH_WRITE) >>> + dbg_reg->dbcr0 |= DBCR0_DAC1W | DBCR0_IDM; >>> + dbg_reg->dac1 = addr; >>> + break; >>> + case 1: >>> + if (type & KVMPPC_DEBUG_WATCH_READ) >>> + dbg_reg->dbcr0 |= DBCR0_DAC2R | DBCR0_IDM; >>> + if (type & KVMPPC_DEBUG_WATCH_WRITE) >>> + dbg_reg->dbcr0 |= DBCR0_DAC2W | DBCR0_IDM; >>> + dbg_reg->dac2 = addr; >>> + break; >>> + default: >>> + return -EINVAL; >>> + } >> >> dbg_reg->dbcr0 |= DBCR0_IDM; >> >>> + return 0; >>> +} >>> + >>> +int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, >>> + struct kvm_guest_debug *dbg) >>> +{ >>> + struct debug_reg *dbg_reg; >>> + int n, b = 0, w = 0; >>> + >>> + if (!(dbg->control & KVM_GUESTDBG_ENABLE)) { >>> + /* Clear All debug events */ >>> + vcpu->arch.shadow_dbg_reg.dbcr0 = 0; >>> + vcpu->guest_debug = 0; >>> +#ifdef CONFIG_KVM_BOOKE_HV >>> + /* >>> + * When user space is not using the debug resources >>> + * then allow guest to change the MSR.DE. >>> + */ >>> + vcpu->arch.shadow_msrp &= ~MSRP_DEP; #endif >> >> guest_may_set_msr_de(vcpu, true); >> >>> + return 0; >>> + } >>> + >>> +#ifdef CONFIG_KVM_BOOKE_HV >>> + /* >>> + * When user space is using the debug resource then >>> + * do not allow guest to change the MSR.DE. >>> + */ >>> + vcpu->arch.shadow_msrp |= MSRP_DEP; >>> +#endif >> >> guest_may_set_msr_de(vcpu, false); >> >>> + vcpu->guest_debug = dbg->control; >>> + vcpu->arch.shadow_dbg_reg.dbcr0 = 0; >>> + /* Set DBCR0_EDM in guest visible DBCR0 register. */ >>> + vcpu->arch.dbg_reg.dbcr0 = DBCR0_EDM; >>> + >>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) >>> + vcpu->arch.shadow_dbg_reg.dbcr0 |= DBCR0_IDM | DBCR0_IC; >>> + >>> + if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)) >>> + return 0; >>> + >>> + /* Code below handles only HW breakpoints */ >>> + dbg_reg = &(vcpu->arch.shadow_dbg_reg); >>> + >>> + /* >>> + * On BOOKE (e500v2); Set DBCR1 and DBCR2 to allow debug events >>> + * to occur when MSR.PR is set. >>> + * On BOOKE-HV (e500mc+); MSR.PR = 0 when guest is running. So we >>> + * should clear DBCR1 and DBCR2. And EPCR.DUVD is used to control >>> + * that debug events will not come in hypervisor (GS = 0). > > Will rework the above comment as discussed. > >> >> This is still wrong. We want to trap in PR=1. It's what PR KVM does, it's what >> TCG does. There is no point in making HV KVM behave differently. > > This comment is not valid. > >> >>> + */ >>> +#ifdef CONFIG_KVM_BOOKE_HV >>> + dbg_reg->dbcr1 = 0; >>> + dbg_reg->dbcr2 = 0; >>> +#else >>> + dbg_reg->dbcr1 = DBCR1_IAC1US | DBCR1_IAC2US | DBCR1_IAC3US | >>> + DBCR1_IAC4US; >>> + dbg_reg->dbcr2 = DBCR2_DAC1US | DBCR2_DAC2US; #endif >>> + >>> + for (n = 0; n < (KVMPPC_BOOKE_IAC_NUM + KVMPPC_BOOKE_DAC_NUM); n++) { >>> + uint64_t addr = dbg->arch.bp[n].addr; >>> + uint32_t type = dbg->arch.bp[n].type; >>> + >>> + if (type == KVMPPC_DEBUG_NONE) >>> + continue; >>> + >>> + if (type & !(KVMPPC_DEBUG_WATCH_READ | >>> + KVMPPC_DEBUG_WATCH_WRITE | >>> + KVMPPC_DEBUG_BREAKPOINT)) >>> + return -EINVAL; >>> + >>> + if (type & KVMPPC_DEBUG_BREAKPOINT) { >>> + /* Setting H/W breakpoint */ >>> + if (kvmppc_booke_set_breakpoint(vcpu, addr, b++)) >> >> Please pass dbg_reg into the function >> >>> + return -EINVAL; >>> + } else { >>> + /* Setting H/W watchpoint */ >>> + if (kvmppc_booke_set_watchpoint(vcpu, addr, type, w++)) >> >> here too >> >>> + return -EINVAL; >>> + } >>> + } >>> + >>> + return 0; >>> +} >>> + >>> void kvmppc_booke_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { >>> vcpu->cpu = smp_processor_id(); >>> @@ -1678,6 +1879,11 @@ void kvmppc_booke_vcpu_put(struct kvm_vcpu >>> *vcpu) { >>> current->thread.kvm_vcpu = NULL; >>> vcpu->cpu = -1; >>> + >>> + /* Disable all debug events */ >>> + mtspr(SPRN_DBCR0, 0x0); >> >> Why? Wouldn't normal preemption handling take care of this already? > > Yes, normal preemption will take care. On vcpu_put we do not clear EPCR.DUVD and DBCR1/2. > So debug event will not be taken in host. > > So yes, it is not needed here. > >> >>> + /* Clear pending debug event in DBSR */ >>> + kvmppc_clear_dbsr(); >> >> Is there a chance we will ever have to do this? On debug exits from guest >> context we already clear dbsr. > > DBSR can have events captured but not delivered as interrupt if MSR.DE is clear. I know with qemu debug stub we do not allow msr.de to be cleared by guest. I see. In that case we'd have to save the original DBSR value into vcpu->arch though, no? Otherwise we might lose guest debug events on preemption if we simply clear it. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
