Re: [PATCH 4/4 v2] KVM: PPC: Add userspace debug stub support

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 03.04.2013, at 19:14, Bhushan Bharat-R65777 wrote:

> 
> 
>> -----Original Message-----
>> From: Alexander Graf [mailto:agraf@xxxxxxx]
>> Sent: Tuesday, April 02, 2013 9:11 PM
>> To: Bhushan Bharat-R65777
>> Cc: kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Wood Scott-B07421
>> Subject: Re: [PATCH 4/4 v2] KVM: PPC: Add userspace debug stub support
>> 
>> On 04/02/2013 04:09 PM, Bhushan Bharat-R65777 wrote:
>>> 
>>>> -----Original Message-----
>>>> From: Alexander Graf [mailto:agraf@xxxxxxx]
>>>> Sent: Tuesday, April 02, 2013 1:57 PM
>>>> To: Bhushan Bharat-R65777
>>>> Cc: kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Wood Scott-B07421
>>>> Subject: Re: [PATCH 4/4 v2] KVM: PPC: Add userspace debug stub
>>>> support
>>>> 
>>>> 
>>>> On 29.03.2013, at 07:04, Bhushan Bharat-R65777 wrote:
>>>> 
>>>>> 
>>>>>> -----Original Message-----
>>>>>> From: Alexander Graf [mailto:agraf@xxxxxxx]
>>>>>> Sent: Thursday, March 28, 2013 10:06 PM
>>>>>> To: Bhushan Bharat-R65777
>>>>>> Cc: kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Wood
>>>>>> Scott-B07421; Bhushan
>>>>>> Bharat-R65777
>>>>>> Subject: Re: [PATCH 4/4 v2] KVM: PPC: Add userspace debug stub
>>>>>> support
>>>>>> 
>>>>>> 
>>>>>> On 21.03.2013, at 07:25, 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.
>>>>>>> 
>>>>>>> Signed-off-by: Bharat Bhushan<bharat.bhushan@xxxxxxxxxxxxx>
>>>>>>> ---
>>>>>>> v2:
>>>>>>> - save/restore in vcpu_get()/vcpu_put()
>>>>>>> - some more minor cleanup based on review comments.
>>>>>>> 
>>>>>>> arch/powerpc/include/asm/kvm_host.h |   10 ++
>>>>>>> arch/powerpc/include/uapi/asm/kvm.h |   22 +++-
>>>>>>> arch/powerpc/kvm/booke.c            |  252
>> ++++++++++++++++++++++++++++++++-
>>>> --
>>>>>>> arch/powerpc/kvm/e500_emulate.c     |   10 ++
>>>>>>> 4 files changed, 272 insertions(+), 22 deletions(-)
>>>>>>> 
>>>>>>> diff --git a/arch/powerpc/include/asm/kvm_host.h
>>>>>>> b/arch/powerpc/include/asm/kvm_host.h
>>>>>>> index f4ba881..8571952 100644
>>>>>>> --- a/arch/powerpc/include/asm/kvm_host.h
>>>>>>> +++ b/arch/powerpc/include/asm/kvm_host.h
>>>>>>> @@ -504,7 +504,17 @@ struct kvm_vcpu_arch {
>>>>>>> 	u32 mmucfg;
>>>>>>> 	u32 epr;
>>>>>>> 	u32 crit_save;
>>>>>>> +	/* guest debug registers*/
>>>>>>> 	struct kvmppc_booke_debug_reg dbg_reg;
>>>>>>> +	/* shadow debug registers */
>>>>>>> +	struct kvmppc_booke_debug_reg shadow_dbg_reg;
>>>>>>> +	/* host debug registers*/
>>>>>>> +	struct kvmppc_booke_debug_reg host_dbg_reg;
>>>>>>> +	/*
>>>>>>> +	 * Flag indicating that debug registers are used by guest
>>>>>>> +	 * and requires save restore.
>>>>>>> +	*/
>>>>>>> +	bool debug_save_restore;
>>>>>>> #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 15f9a00..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_NOTYPE		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
>>>>>>> 1de93a8..bf20056 100644
>>>>>>> --- a/arch/powerpc/kvm/booke.c
>>>>>>> +++ b/arch/powerpc/kvm/booke.c
>>>>>>> @@ -133,6 +133,30 @@ 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. Do not allow guest to change MSR[DE].
>>>>>>> +		 */
>>>>>>> +		vcpu->arch.shared->msr |= MSR_DE;
>>>>>>> +		mtspr(SPRN_MSRP, mfspr(SPRN_MSRP) | MSRP_DEP);
>>>>>> This mtspr should really just be a bit or in shadow_mspr when
>>>>>> guest_debug gets enabled. It should automatically get synchronized
>>>>>> as soon as the next
>>>>>> vpcu_load() happens.
>>>>> I think this is not required here as shadow_dbsr already have MSRP_DEP set.
>>>>> 
>>>>> Will setup shadow_msrp when setting guest_debug and clear
>>>>> shadow_msrp when
>>>> guest_debug is cleared.
>>>>> But that will also not be sufficient as it not sure when vcpu_load()
>>>>> will be called after the shadow_msrp is changed. So
>>>>> 
>>>>> When guest_debug is set in debug_ioctl()
>>>>> /* Set MSRP_DEP in shadow_msrp so that guest cannot change MSR.DE.
>>>>> As shadow_msrp is loaded on vcpu_load(), and it is not guaranteed
>>>>> that
>>>>> vcpu_load() will be called just after debug_ioctl(), so also set
>>>>> MSRP_DEP in SPRN_MSRP. */
>>>> debug_ioctl is an ioctl. So while that ioctl is on, the vcpu is not running.
>>>> After that ioctl user space calls another VCPU_RUN ioctl which
>>>> invokes vcpu_load.
>>> That's good. I was not aware of vcpu_load() is being called before
>>> ioctl handling in KVM :)
>>> 
>>>>> - shadow_msrp | MSRP_DEP;
>>>>> - change SPRN_MSRP.MSRP_DEP as you do not know when vcpu_load() will
>>>>> be
>>>> called?
>>>>> 
>>>>> When guest_debug is cleared in debug_ioctl()
>>>>> /* Clear MSRP_DEP in shadow_msrp so that guest can change MSR.DE. As
>>>>> shadow_msrp is loaded on vcpu_load(), and it is not guaranteed that
>>>>> vcpu_load() will be called just after debug_ioctl(), so also clear
>>>>> MSRP_DEP in SPRN_MSRP. */
>>>> Same thing here again.
>>>> 
>>>>> - shadow_msrp | MSRP_DEP;
>>>>> - change SPRN_MSRP.MSRP_DEP as you do not know when vcpu_load() will
>>>>> be
>>>> called?
>>>>>> Also, what happens when user space disables guest_debug?
>>>>>> 
>>>>>>> +#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 +174,7 @@ 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, @@
>>>>>>> -736,6 +761,9 @@ static int emulation_exit(struct kvm_run *run,
>>>>>>> struct
>>>>>> kvm_vcpu *vcpu)
>>>>>>> 		run->exit_reason = KVM_EXIT_DCR;
>>>>>>> 		return RESUME_HOST;
>>>>>>> 
>>>>>>> +	case EMULATE_EXIT_USER:
>>>>>>> +		return RESUME_HOST;
>>>>>> This should get folded into the previous patch or be a separate one.
>>>>> ok
>>>>> 
>>>>>>> +
>>>>>>> 	case EMULATE_FAIL:
>>>>>>> 		printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",
>>>>>>> 		       __func__, vcpu->arch.pc, vcpu->arch.last_inst); @@ -751,6
>>>>>>> +779,30 @@ static int emulation_exit(struct kvm_run *run, struct
>>>>>>> +kvm_vcpu
>>>>>> *vcpu)
>>>>>>> 	}
>>>>>>> }
>>>>>>> 
>>>>>>> +static int kvmppc_handle_debug(struct kvm_run *run, struct
>>>>>>> +kvm_vcpu
>>>>>>> +*vcpu) {
>>>>>>> +	u32 dbsr = mfspr(SPRN_DBSR);
>>>>>>> +	mtspr(SPRN_DBSR, dbsr);
>>>>>> This definitely deserves a comment :).
>>>>> Ok.
>>>>> 
>>>>>> Also, are we non-preemptible here?
>>>>> This is called from kvmppc_handle_exit and interrupts are enabled,
>>>>> so I think
>>>> this can be preempted.
>>>>> But I do not think there is any issue as we clear DBSR in vpu_put().
>>>> Ok, make clear_dbsr a function then that you call from both places.
>>>> That way it's more obvious.
>>> Ok
>>> 
>>>>>>> +
>>>>>>> +	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;
>>>>>> Shouldn't this check for guest_debug and only go to user space if
>>>>>> it asked for debugging? Can't you just leave it at the old code for
>>>> !guest_debug?
>>>>> Will add, I thought that it is redundant as of now as debug
>>>>> interrupt in guest
>>>> can come only when user space is debugging guest.
>>>> 
>>>> The problem is that user space might not expect a guest debug exit.
>>> Ok
>>> 
>>>>> clear DBSR
>>>>> if (!guest_debug)
>>>>> 	return RESUME_GUEST;
>>>> Can't you just do exactly what was done before when !guest_debug? We
>>>> usually try to change semantics one step at a time.
>>> What you mean by "done before" ? do you mean the removed code in "case
>> BOOKE_INTERRUPT_DEBUG" code in kvmppc_handle_exit() ? If yes then that code was
>> meaningless and not correct.
>> 
>> Then change it in a separate patch. One patch, one change. Otherwise
>> bisectability suffers.
>> 
>>> Right thing should be clear the pending exception and resume the
>>> guest. when no one is in state to handle the exception. May be we can
>>> have WARN_ON_ONCE()
>>> 
>>>>>>> +}
>>>>>>> +
>>>>>>> static void kvmppc_fill_pt_regs(struct pt_regs *regs) {
>>>>>>> 	ulong r1, ip, msr, lr;
>>>>>>> @@ -1110,18 +1162,10 @@ 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;
>>>>>>> 	}
>>>>>>> 
>>>>>>> @@ -1172,7 +1216,7 @@ 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
>>>>>>> @@ -1527,12 +1571,6 @@ 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;
>>>>>>> @@ -1638,16 +1676,194 @@ 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) {
>>>>>>> +	if (!vcpu->arch.debug_save_restore)
>>>>>>> +		return;
>>>>>>> +
>>>>>>> +	/* Restore Host Context. Disable all debug events First */
>>>>>>> +	mtspr(SPRN_DBCR0, 0x0);
>>>>>>> +	/* Disable pending debug event by Clearing DBSR */
>>>>>>> +	mtspr(SPRN_DBSR, mfspr(SPRN_DBSR));
>>>>>>> +
>>>>>>> +	mtspr(SPRN_DBCR1, vcpu->arch.host_dbg_reg.dbcr1);
>>>>>>> +	mtspr(SPRN_DBCR2, vcpu->arch.host_dbg_reg.dbcr2); #ifdef
>>>>>>> +CONFIG_KVM_E500MC
>>>>>>> +	mtspr(SPRN_DBCR4, vcpu->arch.host_dbg_reg.dbcr4); #endif
>>>>>>> +	mtspr(SPRN_IAC1, vcpu->arch.host_dbg_reg.iac[0]);
>>>>>>> +	mtspr(SPRN_IAC2, vcpu->arch.host_dbg_reg.iac[1]); #if
>>>>>>> +CONFIG_PPC_ADV_DEBUG_IACS>  2
>>>>>>> +	mtspr(SPRN_IAC3, vcpu->arch.host_dbg_reg.iac[2]);
>>>>>>> +	mtspr(SPRN_IAC4, vcpu->arch.host_dbg_reg.iac[3]); #endif
>>>>>>> +	mtspr(SPRN_DAC1, vcpu->arch.host_dbg_reg.dac[0]);
>>>>>>> +	mtspr(SPRN_DAC2, vcpu->arch.host_dbg_reg.dac[1]);
>>>>>>> +
>>>>>>> +	/* Enable debug events after all other debug registers restored */
>>>>>>> +	mtspr(SPRN_DBCR0, vcpu->arch.host_dbg_reg.dbcr0);
>>>>>> How does the normal debug register switching code work in Linux?
>>>>>> Can't we just reuse that? Or rely on it to restore working state
>>>>>> when another process gets scheduled in?
>>>>> Good point, I can see debug registers loading in function
>>>>> __switch_to()-
>>>>> switch_booke_debug_regs() in file arch/powerpc/kernel/process.c.
>>>>> So as long as assume that host will not use debug resources we can
>>>>> rely on
>>>> this restore. But I am not sure that this is a fare assumption. As
>>>> Scott earlier mentioned someone can use debug resource for kernel debugging
>> also.
>>>> 
>>>> Someone in the kernel can also use floating point registers. But then
>>>> it's his responsibility to clean up the mess he leaves behind.
>>> I am neither convinced by what you said and nor even have much reason
>>> to oppose :)
>>> 
>>> Scott,
>>> 	I remember you mentioned that host can use debug resources, you comment on
>> this ?
>>> 
>>>>>>> +
>>>>>>> +	/* Host debug register are restored */
>>>>>>> +	vcpu->arch.debug_save_restore = false; }
>>>>>>> +
>>>>>>> +static void kvmppc_booke_vcpu_load_debug_regs(struct kvm_vcpu
>>>>>>> +*vcpu) {
>>>>>>> +	/*
>>>>>>> +	 * Check whether guest still need debug resource, if not then there
>>>>>>> +	 * is no need to resotre guest context.
>>>>>> restore
>>>>>> 
>>>>>>> +	 */
>>>>>>> +	if (!vcpu->arch.shadow_dbg_reg.dbcr0)
>>>>>>> +		return;
>>>>>> Are we guaranteed that debugging is disabled here?
>>>>> Ah, I should be clearing the hw DBCR0 and DBSR.
>>>>> 
>>>>>> We don't want to get debug
>>>>>> exceptions that were meant for some other process.
>>>>>> 
>>>>>>> +
>>>>>>> +	/*
>>>>>>> +	 * Save Host debug register only after restore. If host debug
>>>>>>> +	 * registers are saved and not restored then do not save again.
>>>>>>> +	 */
>>>>>>> +	if (!vcpu->arch.debug_save_restore) {
>>>>>>> +		/* Save Host context */
>>>>>>> +		vcpu->arch.host_dbg_reg.dbcr0 = mfspr(SPRN_DBCR0);
>>>>>>> +		vcpu->arch.host_dbg_reg.dbcr1 = mfspr(SPRN_DBCR1);
>>>>>>> +		vcpu->arch.host_dbg_reg.dbcr2 = mfspr(SPRN_DBCR2); #ifdef
>>>>>>> +CONFIG_KVM_E500MC
>>>>>>> +		vcpu->arch.host_dbg_reg.dbcr4 = mfspr(SPRN_DBCR4); #endif
>>>>>>> +		vcpu->arch.host_dbg_reg.iac[0] = mfspr(SPRN_IAC1);
>>>>>>> +		vcpu->arch.host_dbg_reg.iac[1] = mfspr(SPRN_IAC2); #if
>>>>>>> +CONFIG_PPC_ADV_DEBUG_IACS>  2
>>>>>>> +		vcpu->arch.host_dbg_reg.iac[2] = mfspr(SPRN_IAC3);
>>>>>>> +		vcpu->arch.host_dbg_reg.iac[3] = mfspr(SPRN_IAC4); #endif
>>>>>>> +		vcpu->arch.host_dbg_reg.dac[0] = mfspr(SPRN_DAC1);
>>>>>>> +		vcpu->arch.host_dbg_reg.dac[1] = mfspr(SPRN_DAC2);
>>>>>>> +		vcpu->arch.debug_save_restore = true;
>>>>>>> +	}
>>>>>>> +
>>>>>>> +	/* Restore Guest Context. Disable all debug events First */
>>>>>>> +	mtspr(SPRN_DBCR0, 0x0);
>>>>>>> +	/* Clear h/w DBSR */
>>>>>>> +	mtspr(SPRN_DBSR, mfspr(SPRN_DBSR));
>>>>>>> +
>>>>>>> +	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); #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); }
>>>>>>> +
>>>>>>> +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;
>>>>>> Ah, this is where we disable guest_debug. This needs to enable
>>>>>> guest_debug for the guest again, so you need to remove the DE bit
>>>>>> from
>>>> shadow_msrp here.
>>>>>>> +		return 0;
>>>>>>> +	}
>>>>>>> +
>>>>>>> +	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 */
>>>>>>> +		kvmppc_booke_vcpu_load_debug_regs(vcpu);
>>>>>>> +		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.
>>>>>>> +	 */
>>>>>>> +#ifdef CONFIG_KVM_BOOKE_HV
>>>>>>> +	dbg_reg->dbcr1 = 0;
>>>>>>> +	dbg_reg->dbcr2 = 0;
>>>>>> Does that mean we can't debug guest user space?
>>>>> Yes
>>>> This is wrong.
>>> Really, So far I am assuming qemu debug stub is not mean for debugging guest
>> application.
>> 
>> Ok, let me rephrase: This is confusing. You do trap in PR mode on e500v2. IIRC
>> x86 also traps in kernel and user space. I don't see why e500 hv should be
>> different.
> 
> I am sorry, I think did not read the document correctly.
> 
> DBCR1 = 0 ; means the "00 IAC1 debug conditions unaffected by MSR[PR],MSR[GS].
> 
> Similarly for dbcr2. 
> 
> So yes the guest user space can be debugged.

So why is this conditional on BOOKE_HV then? Wouldn't it make things easier to treat HV and PR identical?


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




[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux