> -----Original Message-----
> From: Alexander Graf [mailto:[email protected]]
> Sent: Friday, April 26, 2013 4:46 PM
> To: Bhushan Bharat-R65777
> Cc: [email protected]; [email protected]; Wood Scott-B07421; Bhushan
> Bharat-R65777
> Subject: Re: [PATCH 7/7 v3] KVM: PPC: Add userspace debug stub support
>
>
> On 08.04.2013, at 12:32, Bharat Bhushan wrote:
>
> > From: Bharat Bhushan <[email protected]>
> >
> > 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 <[email protected]>
> > ---
> > 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)
>
> ...
Please tell What does "..." mean. Does that mean next comment is about the
above function?
>
> > +{
> > + 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.
ok
>
> > +#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?
I think we can if
- Save thread->debug_regs in local data structure
- Load vcpu->arch->debug_regs in thread->debug_regs
- Call prime_debug_regs();
- Restore thread->debug_regs from local save values in first step
>
> > +
> > 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;
Ok
>
> > + 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.
kvmppc_booke_vcpu_load_debug_regs(vcpu); cleares DBSR and DBCR0, even if
previous process have used debug registers. Is not that sufficient? I do not
think we should load all other registers.
>
> > +
> > 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?
Want to clarify, preemption will be enabled on calling local_irq_enable(); in
kvmppc_handle_exit()?
> So we can have a
> debug event that gets cleared on preempt by this.
Should we read the DBSR in before local_irq_enable() in kvmppc_handle_exit()?
>
> > +}
> > +
> > +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?
Yes :-)
>
> > +#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.
Ok
>
> > + 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.
Userspce does following
- dbg->arch.bp[] is first zero initialized. So dbg->arch.bp[n].type is 0
(KVMPPC_DEBUG_NONE)
- Then set following for valid breakpoints/watchpoints:
-- dbg->arch.bp[n].type (KVMPPC_DEBUG_BREAKPOINT or KVMPPC_DEBUG_WATCH_WRITE
or KVMPPC_DEBUG_WATCH_READ)
-- dbg->arch.bp[n].addr
I tried to avoid loop when type is 0 (probably saying type == KVMPPC_DEBUG_NONE
should be more clear).
if type is invalid then should we return -EINVAL.
-Bharat
>
>
> 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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>
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