On 08.04.2013, at 12:32, Bharat Bhushan wrote:
> From: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>
>
> 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.
>
> Debug registers are saved/restored on vcpu_put()/vcpu_get().
> Also the debug registers are saved restored only if guest
> is using debug resources.
>
> 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. 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 | 8 +
> arch/powerpc/include/uapi/asm/kvm.h | 22 +++-
> arch/powerpc/kvm/booke.c | 242 ++++++++++++++++++++++++++++++++---
> arch/powerpc/kvm/booke.h | 5 +
> 4 files changed, 255 insertions(+), 22 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index e34f8fe..b9ad20f 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -505,7 +505,15 @@ struct kvm_vcpu_arch {
> u32 mmucfg;
> u32 epr;
> u32 crit_save;
> +
> + /* Flag indicating that debug registers are used by guest */
> + bool debug_active;
> + /* for save/restore thread->dbcr0 on vcpu run/heavyweight_exit */
> + u32 saved_dbcr0;
> + /* guest debug registers*/
> struct kvmppc_booke_debug_reg dbg_reg;
> + /* shadow debug registers */
> + struct kvmppc_booke_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 c0c38ed..d7ce449 100644
> --- a/arch/powerpc/include/uapi/asm/kvm.h
> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> @@ -25,6 +25,7 @@
> /* Select powerpc specific features in <linux/kvm.h> */
> #define __KVM_HAVE_SPAPR_TCE
> #define __KVM_HAVE_PPC_SMT
> +#define __KVM_HAVE_GUEST_DEBUG
>
> struct kvm_regs {
> __u64 pc;
> @@ -267,7 +268,24 @@ struct kvm_fpu {
> __u64 fpr[32];
> };
>
> +/*
> + * Defines for h/w breakpoint, watchpoint (read, write or both) and
> + * software breakpoint.
> + * These are used as "type" in KVM_SET_GUEST_DEBUG ioctl and "status"
> + * for KVM_DEBUG_EXIT.
> + */
> +#define KVMPPC_DEBUG_NONE 0x0
> +#define KVMPPC_DEBUG_BREAKPOINT (1UL << 1)
> +#define KVMPPC_DEBUG_WATCH_WRITE (1UL << 2)
> +#define KVMPPC_DEBUG_WATCH_READ (1UL << 3)
> struct kvm_debug_exit_arch {
> + __u64 address;
> + /*
> + * exiting to userspace because of h/w breakpoint, watchpoint
> + * (read, write or both) and software breakpoint.
> + */
> + __u32 status;
> + __u32 reserved;
> };
>
> /* for KVM_SET_GUEST_DEBUG */
> @@ -279,10 +297,6 @@ struct kvm_guest_debug_arch {
> * Type denotes h/w breakpoint, read watchpoint, write
> * watchpoint or watchpoint (both read and write).
> */
> -#define KVMPPC_DEBUG_NONE 0x0
> -#define KVMPPC_DEBUG_BREAKPOINT (1UL << 1)
> -#define KVMPPC_DEBUG_WATCH_WRITE (1UL << 2)
> -#define KVMPPC_DEBUG_WATCH_READ (1UL << 3)
> __u32 type;
> __u32 reserved;
> } bp[16];
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 97ae158..0e93416 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,
> @@ -646,6 +670,46 @@ int kvmppc_core_check_requests(struct kvm_vcpu *vcpu)
> return r;
> }
>
> +static void kvmppc_load_usespace_gebug(void)
...
> +{
> + switch_booke_debug_regs(¤t->thread);
> +}
> +
> +static void kvmppc_booke_vcpu_load_debug_regs(struct kvm_vcpu *vcpu)
> +{
> + if (!vcpu->arch.debug_active)
> + return;
> +
> + /* Disable all debug events and clead pending debug events */
> + mtspr(SPRN_DBCR0, 0x0);
> + kvmppc_clear_dbsr();
> +
> + /*
> + * Check whether guest still need debug resource, if not then there
> + * is no need to restore guest context.
> + */
> + if (!vcpu->arch.shadow_dbg_reg.dbcr0)
> + return;
> +
> + /* Load Guest Context */
> + mtspr(SPRN_DBCR1, vcpu->arch.shadow_dbg_reg.dbcr1);
> + mtspr(SPRN_DBCR2, vcpu->arch.shadow_dbg_reg.dbcr2);
> +#ifdef CONFIG_KVM_E500MC
> + mtspr(SPRN_DBCR4, vcpu->arch.shadow_dbg_reg.dbcr4);
You need to make sure DBCR4 is 0 when you leave things back to normal user space. Otherwise guest debug can interfere with host debug.
> +#endif
> + mtspr(SPRN_IAC1, vcpu->arch.shadow_dbg_reg.iac[0]);
> + mtspr(SPRN_IAC2, vcpu->arch.shadow_dbg_reg.iac[1]);
> +#if CONFIG_PPC_ADV_DEBUG_IACS > 2
> + mtspr(SPRN_IAC3, vcpu->arch.shadow_dbg_reg.iac[2]);
> + mtspr(SPRN_IAC4, vcpu->arch.shadow_dbg_reg.iac[3]);
> +#endif
> + mtspr(SPRN_DAC1, vcpu->arch.shadow_dbg_reg.dac[0]);
> + mtspr(SPRN_DAC2, vcpu->arch.shadow_dbg_reg.dac[1]);
> +
> + /* Enable debug events after other debug registers restored */
> + mtspr(SPRN_DBCR0, vcpu->arch.shadow_dbg_reg.dbcr0);
> +}
All of the code above looks suspiciously similar to prime_debug_regs();. Can't we somehow reuse that?
> +
> int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> {
> int ret, s;
> @@ -693,11 +757,25 @@ 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.
> + */
> + vcpu->arch.debug_active = 1;
= true;
> + vcpu->arch.saved_dbcr0 = current->thread.dbcr0;
> + current->thread.dbcr0 = 0;
> + kvmppc_booke_vcpu_load_debug_regs(vcpu);
static void switch_booke_debug_regs(struct thread_struct *new_thread)
{
if ((current->thread.dbcr0 & DBCR0_IDM)
|| (new_thread->dbcr0 & DBCR0_IDM))
prime_debug_regs(new_thread);
}
The kernel will also restore debug state if the process we come from has debugging enabled. Please adjust the comment accordingly.
> +
> 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 thread->dbcr0 */
> + vcpu->arch.debug_active = 0;
> + current->thread.dbcr0 = vcpu->arch.saved_dbcr0;
> + kvmppc_load_usespace_gebug();
> +
> #ifdef CONFIG_PPC_FPU
> kvmppc_save_guest_fp(vcpu);
>
> @@ -753,6 +831,36 @@ 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.
> + */
> +static int kvmppc_handle_debug(struct kvm_run *run, struct kvm_vcpu *vcpu)
> +{
> + u32 dbsr = mfspr(SPRN_DBSR);
> +
> + kvmppc_clear_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 = vcpu->arch.shadow_dbg_reg.dac[0];
> + else if (dbsr & (DBSR_DAC2R | DBSR_DAC2W))
> + run->debug.arch.address = vcpu->arch.shadow_dbg_reg.dac[1];
> + }
> +
> + return RESUME_HOST;
> +}
> +
> static void kvmppc_fill_pt_regs(struct pt_regs *regs)
> {
> ulong r1, ip, msr, lr;
> @@ -1112,18 +1220,10 @@ 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;
> }
>
> @@ -1174,7 +1274,7 @@ 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
> @@ -1529,12 +1629,6 @@ 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;
> @@ -1640,16 +1734,128 @@ void kvmppc_decrementer_func(unsigned long data)
> kvmppc_set_tsr_bits(vcpu, TSR_DIS);
> }
>
> +static void kvmppc_booke_vcpu_put_debug_regs(struct kvm_vcpu *vcpu)
> +{
> + /* Disable all debug events First */
first
> + mtspr(SPRN_DBCR0, 0x0);
> + /* Disable pending debug event by clearing DBSR */
> + kvmppc_clear_dbsr();
kvmppc_handle_debug() happens with preemption enabled, no? So we can have a debug event that gets cleared on preempt by this.
> +}
> +
> +int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> + struct kvm_guest_debug *dbg)
> +{
> + struct kvmppc_booke_debug_reg *dbg_reg;
> + int n, b = 0, w = 0;
> + const u32 bp_code[] = {
> + DBCR0_IAC1 | DBCR0_IDM,
> + DBCR0_IAC2 | DBCR0_IDM,
> + DBCR0_IAC3 | DBCR0_IDM,
> + DBCR0_IAC4 | DBCR0_IDM
> + };
> + const u32 wp_code[] = {
> + DBCR0_DAC1W | DBCR0_IDM,
> + DBCR0_DAC2W | DBCR0_IDM,
> + DBCR0_DAC1R | DBCR0_IDM,
> + DBCR0_DAC2R | DBCR0_IDM
> + };
> +
> + 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
> + 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;
This is supposed to be |= right?
> +#endif
> + 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))
> + /* Code below handles only HW breakpoints */
Please move the comment out of the one-lined branch. Just put it below the return.
> + return 0;
> +
> + 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).
> + */
> +#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++) {
> + u32 type = dbg->arch.bp[n].type;
> +
> + if (!type)
> + continue;
Scott's comment on why a zero-type is different from any other invalid type is still outstanding I think.
Alex
> +
> + if (type & (KVMPPC_DEBUG_WATCH_READ |
> + KVMPPC_DEBUG_WATCH_WRITE)) {
> + if (w >= KVMPPC_BOOKE_DAC_NUM)
> + return -EINVAL;
> +
> + if (type & KVMPPC_DEBUG_WATCH_READ)
> + dbg_reg->dbcr0 |= wp_code[w + 2];
> + if (type & KVMPPC_DEBUG_WATCH_WRITE)
> + dbg_reg->dbcr0 |= wp_code[w];
> +
> + dbg_reg->dac[w] = dbg->arch.bp[n].addr;
> + w++;
> + } else if (type & KVMPPC_DEBUG_BREAKPOINT) {
> + if (b >= KVMPPC_BOOKE_IAC_NUM)
> + return -EINVAL;
> +
> + dbg_reg->dbcr0 |= bp_code[b];
> + dbg_reg->iac[b] = dbg->arch.bp[n].addr;
> + b++;
> + }
> + }
> +
> + return 0;
> +}
> +
> void kvmppc_booke_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> {
> vcpu->cpu = smp_processor_id();
> current->thread.kvm_vcpu = vcpu;
> +
> + kvmppc_booke_vcpu_load_debug_regs(vcpu);
> }
>
> void kvmppc_booke_vcpu_put(struct kvm_vcpu *vcpu)
> {
> current->thread.kvm_vcpu = NULL;
> vcpu->cpu = -1;
> +
> + kvmppc_booke_vcpu_put_debug_regs(vcpu);
> }
>
> int __init kvmppc_booke_init(void)
> diff --git a/arch/powerpc/kvm/booke.h b/arch/powerpc/kvm/booke.h
> index 5fd1ba6..a1ff67d 100644
> --- a/arch/powerpc/kvm/booke.h
> +++ b/arch/powerpc/kvm/booke.h
> @@ -129,4 +129,9 @@ static inline void kvmppc_save_guest_fp(struct kvm_vcpu *vcpu)
> giveup_fpu(current);
> #endif
> }
> +
> +static inline void kvmppc_clear_dbsr(void)
> +{
> + mtspr(SPRN_DBSR, mfspr(SPRN_DBSR));
> +}
> #endif /* __KVM_BOOKE_H__ */
> --
> 1.7.0.4
>
>
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