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[4/7] KVM: arm64: guest debug, add SW break point support

Message ID 1416931805-23223-5-git-send-email-alex.bennee@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Alex Bennée Nov. 25, 2014, 4:10 p.m. UTC 
This adds support for SW breakpoints inserted by userspace.

First we need to trap all BKPT exceptions in the hypervisor (ELS). This
in controlled through the MDCR_EL2 register. I've added a new field to
the vcpu structure to hold this value. There should be scope to
rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT
manipulation in later patches.

Once the exception arrives we triggers an exit from the main hypervisor
loop to the hypervisor controller. The kvm_debug_exit_arch carries the
address of the exception. If the controller doesn't know of breakpoint
then we have a guest inserted breakpoint and the hypervisor needs to
start again and deliver the exception to guest.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Comments

Andrew Jones Nov. 26, 2014, 4:07 p.m. UTC | #1 
On Tue, Nov 25, 2014 at 04:10:02PM +0000, Alex Bennée wrote:
> This adds support for SW breakpoints inserted by userspace.
> 
> First we need to trap all BKPT exceptions in the hypervisor (ELS). This
> in controlled through the MDCR_EL2 register. I've added a new field to
> the vcpu structure to hold this value. There should be scope to
> rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT
> manipulation in later patches.

I think we should start using the new mdcr_el2 field everywhere we plan
to within the same series that it is introduced. Otherwise it's hard
to tell if we need an mdcr_el2 field, or if a more generic field would
suffice. We can always translate bits of a more generic field to
mdcr_el2 bits when necessary, but not the reverse.

> 
> Once the exception arrives we triggers an exit from the main hypervisor
s/triggers/trigger/
 
> loop to the hypervisor controller. The kvm_debug_exit_arch carries the
> address of the exception. If the controller doesn't know of breakpoint
                                                             ^ a
> then we have a guest inserted breakpoint and the hypervisor needs to
> start again and deliver the exception to guest.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 2c6386e..9383359 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2592,7 +2592,7 @@ when running. Common control bits are:
>  The top 16 bits of the control field are architecture specific control
>  flags which can include the following:
>  
> -  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86]
> +  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86, arm64]
>    - KVM_GUESTDBG_USE_HW_BP:     using hardware breakpoints [x86, s390]
>    - KVM_GUESTDBG_INJECT_DB:     inject DB type exception [x86]
>    - KVM_GUESTDBG_INJECT_BP:     inject BP type exception [x86]
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index a0ff410..48d26bb 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -303,6 +303,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>  int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  					struct kvm_guest_debug *dbg)
>  {
> +	/* Route debug traps to el2? */
> +	bool route_el2 = false;
> +
>  	/* If it's not enabled clear all flags */
>  	if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
>  		vcpu->guest_debug = 0;
> @@ -320,8 +323,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  
>  	/* Software Break Points */
>  	if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
> -		kvm_info("SW BP support requested, not yet implemented\n");
> -		return -EINVAL;
> +		kvm_info("SW BP support requested\n");
> +		route_el2 = true;
>  	}
>  
>  	/* Hardware assisted Break and Watch points */
> @@ -330,6 +333,20 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  		return -EINVAL;
>  	}
>  
> +	/* If we are going to handle any debug exceptions we need to
> +	 * set MDCE_EL2.TDE to ensure they are routed to the
> +	 * hypervisor. If userspace determines the exception was
> +	 * actually internal to the guest it needs to handle
> +	 * re-injecting the exception.
> +	 */

kernel comment blocks typically start with an empty line, e.g.
/*
 * comment block
 */

> +	if (route_el2) {
> +		kvm_info("routing debug exceptions");
> +		vcpu->arch.mdcr_el2 = MDCR_EL2_TDE;
> +	} else {
> +		kvm_info("not routing debug exceptions");
> +		vcpu->arch.mdcr_el2 = 0;
> +	}

This looks weird because we're only managing some of the mdcr_el2 bits
with the mdcr_el2 field. If we were managing all of them then these
would need to be |= MDCR_EL2_TDE and &= ~SOME_MASK instead. If we never
plan to manage all the bits, then I think that points more towards the
need for a more generic field instead.

> +
>  	return 0;
>  }
>  
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 2012c4b..38b0f07 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -98,6 +98,7 @@ struct kvm_vcpu_arch {
>  
>  	/* HYP configuration */
>  	u64 hcr_el2;
> +	u32 mdcr_el2;
>  
>  	/* Exception Information */
>  	struct kvm_vcpu_fault_info fault;
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 9a9fce0..8da1043 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -122,6 +122,7 @@ int main(void)
>    DEFINE(VCPU_HPFAR_EL2,	offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
>    DEFINE(VCPU_DEBUG_FLAGS,	offsetof(struct kvm_vcpu, arch.debug_flags));
>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
> +  DEFINE(VCPU_MDCR_EL2,	offsetof(struct kvm_vcpu, arch.mdcr_el2));
>    DEFINE(VCPU_IRQ_LINES,	offsetof(struct kvm_vcpu, arch.irq_lines));
>    DEFINE(VCPU_HOST_CONTEXT,	offsetof(struct kvm_vcpu, arch.host_cpu_context));
>    DEFINE(VCPU_TIMER_CNTV_CTL,	offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 34b8bd0..28dc92b 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -71,6 +71,26 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  	return 1;
>  }
>  
> +/**
> + * kvm_handle_bkpt - handle a break-point instruction
> + *
> + * @vcpu:	the vcpu pointer

I see you inherited this header format from kvm_handle_wfx, which
probably left @run off the input list because it doesn't use it.
We do use it in this handler though, so we should probably list it.

> + *
> + * By definition if we arrive here it's because we are routing
> + * all SW breakpoints to the hyper-visor as some may be a result of
> + * guest debugging. If user-space decides this particular break-point
> + * isn't for the host to handle it can re-feed the exception to the
> + * guest.
> + */
> +static int kvm_handle_bkpt(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> +	run->exit_reason = KVM_EXIT_DEBUG;
> +	run->debug.arch.exit_type = KVM_DEBUG_EXIT_SW_BKPT;
> +	run->debug.arch.address = *vcpu_pc(vcpu);
> +	kvm_info("exiting from %llx\n", run->debug.arch.address);

*Must* get rid of this kvm_info, else log explosion shall occur.

> +	return 0;
> +}
> +
>  static exit_handle_fn arm_exit_handlers[] = {
>  	[ESR_EL2_EC_WFI]	= kvm_handle_wfx,
>  	[ESR_EL2_EC_CP15_32]	= kvm_handle_cp15_32,
> @@ -85,6 +105,8 @@ static exit_handle_fn arm_exit_handlers[] = {
>  	[ESR_EL2_EC_SYS64]	= kvm_handle_sys_reg,
>  	[ESR_EL2_EC_IABT]	= kvm_handle_guest_abort,
>  	[ESR_EL2_EC_DABT]	= kvm_handle_guest_abort,
> +	[ESR_EL2_EC_BKPT32]	= kvm_handle_bkpt,
> +	[ESR_EL2_EC_BRK64]	= kvm_handle_bkpt,
>  };

There appears to be a typo in the ARM ARM. Subsection "Software
Breakpoint Instruction exception" of D1.10.4 says BRK (ESR_EL2_EC_BRK64)
is 0x39, but the table above that has it correctly as 0x3c. (This
comment doesn't really have anything to do with your patch, but I
thought I'd call it out here as I just noticed it while reading that
section for this review.)

>  
>  static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index b72aa9f..3c733ea 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -772,6 +772,10 @@
>  	orr	x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
>  	orr	x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
>  
> +	// Any other bits (currently TDE)
> +	ldr	x3, [x0, #VCPU_MDCR_EL2]
> +	orr	x2, x2, x3

I've already commented on my opinions on only partially managing
mdcr_el2 bits with the new field.

> +
>  	// Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap
>  	// if not dirty.
>  	ldr	x3, [x0, #VCPU_DEBUG_FLAGS]
> -- 
> 2.1.3
> 
> _______________________________________________
> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
Peter Maydell Nov. 26, 2014, 5:14 p.m. UTC | #2 
On 26 November 2014 at 16:07, Andrew Jones <drjones@redhat.com> wrote:
> There appears to be a typo in the ARM ARM. Subsection "Software
> Breakpoint Instruction exception" of D1.10.4 says BRK (ESR_EL2_EC_BRK64)
> is 0x39, but the table above that has it correctly as 0x3c.

Thanks for pointing out this typo -- I've reported it to the
appropriate documentation people.

-- PMM
Christoffer Dall Nov. 29, 2014, 4:21 p.m. UTC | #3 
On Tue, Nov 25, 2014 at 04:10:02PM +0000, Alex Bennée wrote:
> This adds support for SW breakpoints inserted by userspace.
> 
> First we need to trap all BKPT exceptions in the hypervisor (ELS). This
> in controlled through the MDCR_EL2 register. I've added a new field to

this is ?

> the vcpu structure to hold this value. There should be scope to
> rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT
> manipulation in later patches.

I don't understand what you mean with rationalising something in later
patches.

> 
> Once the exception arrives we triggers an exit from the main hypervisor
> loop to the hypervisor controller. The kvm_debug_exit_arch carries the

hypervisor controller is userspace?

> address of the exception. If the controller doesn't know of breakpoint

the breakint ?

> then we have a guest inserted breakpoint and the hypervisor needs to
> start again and deliver the exception to guest.

to the guest

> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 2c6386e..9383359 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2592,7 +2592,7 @@ when running. Common control bits are:
>  The top 16 bits of the control field are architecture specific control
>  flags which can include the following:
>  
> -  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86]
> +  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86, arm64]
>    - KVM_GUESTDBG_USE_HW_BP:     using hardware breakpoints [x86, s390]
>    - KVM_GUESTDBG_INJECT_DB:     inject DB type exception [x86]
>    - KVM_GUESTDBG_INJECT_BP:     inject BP type exception [x86]
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index a0ff410..48d26bb 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -303,6 +303,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>  int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  					struct kvm_guest_debug *dbg)
>  {
> +	/* Route debug traps to el2? */
> +	bool route_el2 = false;
> +
>  	/* If it's not enabled clear all flags */
>  	if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
>  		vcpu->guest_debug = 0;
> @@ -320,8 +323,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  
>  	/* Software Break Points */
>  	if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
> -		kvm_info("SW BP support requested, not yet implemented\n");
> -		return -EINVAL;
> +		kvm_info("SW BP support requested\n");
> +		route_el2 = true;
>  	}
>  
>  	/* Hardware assisted Break and Watch points */
> @@ -330,6 +333,20 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>  		return -EINVAL;
>  	}
>  
> +	/* If we are going to handle any debug exceptions we need to

wings on the comments

> +	 * set MDCE_EL2.TDE to ensure they are routed to the
> +	 * hypervisor. If userspace determines the exception was
> +	 * actually internal to the guest it needs to handle
> +	 * re-injecting the exception.
> +	 */
> +	if (route_el2) {
> +		kvm_info("routing debug exceptions");
> +		vcpu->arch.mdcr_el2 = MDCR_EL2_TDE;
> +	} else {
> +		kvm_info("not routing debug exceptions");
> +		vcpu->arch.mdcr_el2 = 0;
> +	}
> +
>  	return 0;
>  }
>  
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 2012c4b..38b0f07 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -98,6 +98,7 @@ struct kvm_vcpu_arch {
>  
>  	/* HYP configuration */
>  	u64 hcr_el2;
> +	u32 mdcr_el2;
>  
>  	/* Exception Information */
>  	struct kvm_vcpu_fault_info fault;
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 9a9fce0..8da1043 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -122,6 +122,7 @@ int main(void)
>    DEFINE(VCPU_HPFAR_EL2,	offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
>    DEFINE(VCPU_DEBUG_FLAGS,	offsetof(struct kvm_vcpu, arch.debug_flags));
>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
> +  DEFINE(VCPU_MDCR_EL2,	offsetof(struct kvm_vcpu, arch.mdcr_el2));
>    DEFINE(VCPU_IRQ_LINES,	offsetof(struct kvm_vcpu, arch.irq_lines));
>    DEFINE(VCPU_HOST_CONTEXT,	offsetof(struct kvm_vcpu, arch.host_cpu_context));
>    DEFINE(VCPU_TIMER_CNTV_CTL,	offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 34b8bd0..28dc92b 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -71,6 +71,26 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  	return 1;
>  }
>  
> +/**
> + * kvm_handle_bkpt - handle a break-point instruction
> + *
> + * @vcpu:	the vcpu pointer
> + *
> + * By definition if we arrive here it's because we are routing
> + * all SW breakpoints to the hyper-visor as some may be a result of

s/hyper-visor/hypervisor/

this sentence is weird. I think what you want is a full stop after
hypervisor and then a new sentence: Userspace may decide that this
particular breakpoint should be routed to the guest (if the breakpoint
does not come form userspace but by someone debugging a process inside
the guest), and in that case inject a software breakpoint instruction by
<insert the method here>.



> + * guest debugging. If user-space decides this particular break-point
> + * isn't for the host to handle it can re-feed the exception to the
> + * guest.
> + */
> +static int kvm_handle_bkpt(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> +	run->exit_reason = KVM_EXIT_DEBUG;
> +	run->debug.arch.exit_type = KVM_DEBUG_EXIT_SW_BKPT;
> +	run->debug.arch.address = *vcpu_pc(vcpu);
> +	kvm_info("exiting from %llx\n", run->debug.arch.address);
> +	return 0;
> +}
> +
>  static exit_handle_fn arm_exit_handlers[] = {
>  	[ESR_EL2_EC_WFI]	= kvm_handle_wfx,
>  	[ESR_EL2_EC_CP15_32]	= kvm_handle_cp15_32,
> @@ -85,6 +105,8 @@ static exit_handle_fn arm_exit_handlers[] = {
>  	[ESR_EL2_EC_SYS64]	= kvm_handle_sys_reg,
>  	[ESR_EL2_EC_IABT]	= kvm_handle_guest_abort,
>  	[ESR_EL2_EC_DABT]	= kvm_handle_guest_abort,
> +	[ESR_EL2_EC_BKPT32]	= kvm_handle_bkpt,
> +	[ESR_EL2_EC_BRK64]	= kvm_handle_bkpt,
>  };
>  
>  static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index b72aa9f..3c733ea 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -772,6 +772,10 @@
>  	orr	x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
>  	orr	x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
>  
> +	// Any other bits (currently TDE)
> +	ldr	x3, [x0, #VCPU_MDCR_EL2]
> +	orr	x2, x2, x3
> +
>  	// Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap
>  	// if not dirty.
>  	ldr	x3, [x0, #VCPU_DEBUG_FLAGS]
> -- 
> 2.1.3
> 

It may be simpler to just load/restore the MDCR_EL2 and do all
bit-manipulations for a specific VCPU in C-code instead of this.

-Christoffer
Christoffer Dall Nov. 29, 2014, 4:21 p.m. UTC | #4 
On Wed, Nov 26, 2014 at 05:07:20PM +0100, Andrew Jones wrote:
> On Tue, Nov 25, 2014 at 04:10:02PM +0000, Alex Bennée wrote:
> > This adds support for SW breakpoints inserted by userspace.
> > 
> > First we need to trap all BKPT exceptions in the hypervisor (ELS). This
> > in controlled through the MDCR_EL2 register. I've added a new field to
> > the vcpu structure to hold this value. There should be scope to
> > rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT
> > manipulation in later patches.
> 
> I think we should start using the new mdcr_el2 field everywhere we plan
> to within the same series that it is introduced. Otherwise it's hard
> to tell if we need an mdcr_el2 field, or if a more generic field would
> suffice. We can always translate bits of a more generic field to
> mdcr_el2 bits when necessary, but not the reverse.
> 
Agreed, this is getting messy already with this patch.

-Christoffer
Alex Bennée Dec. 1, 2014, 11:33 a.m. UTC | #5 
Christoffer Dall <christoffer.dall@linaro.org> writes:

> On Tue, Nov 25, 2014 at 04:10:02PM +0000, Alex Bennée wrote:
>> This adds support for SW breakpoints inserted by userspace.
>> 
>> First we need to trap all BKPT exceptions in the hypervisor (ELS). This
>> in controlled through the MDCR_EL2 register. I've added a new field to
>
> this is ?
>
>> the vcpu structure to hold this value. There should be scope to
>> rationlise this with the VCPU_DEBUG_FLAGS/KVM_ARM64_DEBUG_DIRTY_SHIFT
>> manipulation in later patches.
>
> I don't understand what you mean with rationalising something in later
> patches.

I was pointing to potential future improvements. I'm wary of touching
the lazy register syncing code in this patch set as it greatly increases
the scope of testing. However I guess I'll have to bite the bullet and
merge it in a sensible way.

>
>> 
>> Once the exception arrives we triggers an exit from the main hypervisor
>> loop to the hypervisor controller. The kvm_debug_exit_arch carries the
>
> hypervisor controller is userspace?

Yeah sorry that one sneaked through.

>
>> address of the exception. If the controller doesn't know of breakpoint
>
> the breakint ?
>
>> then we have a guest inserted breakpoint and the hypervisor needs to
>> start again and deliver the exception to guest.
>
> to the guest
>
>> 
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> 
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index 2c6386e..9383359 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -2592,7 +2592,7 @@ when running. Common control bits are:
>>  The top 16 bits of the control field are architecture specific control
>>  flags which can include the following:
>>  
>> -  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86]
>> +  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86, arm64]
>>    - KVM_GUESTDBG_USE_HW_BP:     using hardware breakpoints [x86, s390]
>>    - KVM_GUESTDBG_INJECT_DB:     inject DB type exception [x86]
>>    - KVM_GUESTDBG_INJECT_BP:     inject BP type exception [x86]
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index a0ff410..48d26bb 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -303,6 +303,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>>  int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>>  					struct kvm_guest_debug *dbg)
>>  {
>> +	/* Route debug traps to el2? */
>> +	bool route_el2 = false;
>> +
>>  	/* If it's not enabled clear all flags */
>>  	if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
>>  		vcpu->guest_debug = 0;
>> @@ -320,8 +323,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>>  
>>  	/* Software Break Points */
>>  	if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
>> -		kvm_info("SW BP support requested, not yet implemented\n");
>> -		return -EINVAL;
>> +		kvm_info("SW BP support requested\n");
>> +		route_el2 = true;
>>  	}
>>  
>>  	/* Hardware assisted Break and Watch points */
>> @@ -330,6 +333,20 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>>  		return -EINVAL;
>>  	}
>>  
>> +	/* If we are going to handle any debug exceptions we need to
>
> wings on the comments
>
>> +	 * set MDCE_EL2.TDE to ensure they are routed to the
>> +	 * hypervisor. If userspace determines the exception was
>> +	 * actually internal to the guest it needs to handle
>> +	 * re-injecting the exception.
>> +	 */
>> +	if (route_el2) {
>> +		kvm_info("routing debug exceptions");
>> +		vcpu->arch.mdcr_el2 = MDCR_EL2_TDE;
>> +	} else {
>> +		kvm_info("not routing debug exceptions");
>> +		vcpu->arch.mdcr_el2 = 0;
>> +	}
>> +
>>  	return 0;
>>  }
>>  
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 2012c4b..38b0f07 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -98,6 +98,7 @@ struct kvm_vcpu_arch {
>>  
>>  	/* HYP configuration */
>>  	u64 hcr_el2;
>> +	u32 mdcr_el2;
>>  
>>  	/* Exception Information */
>>  	struct kvm_vcpu_fault_info fault;
>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
>> index 9a9fce0..8da1043 100644
>> --- a/arch/arm64/kernel/asm-offsets.c
>> +++ b/arch/arm64/kernel/asm-offsets.c
>> @@ -122,6 +122,7 @@ int main(void)
>>    DEFINE(VCPU_HPFAR_EL2,	offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
>>    DEFINE(VCPU_DEBUG_FLAGS,	offsetof(struct kvm_vcpu, arch.debug_flags));
>>    DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
>> +  DEFINE(VCPU_MDCR_EL2,	offsetof(struct kvm_vcpu, arch.mdcr_el2));
>>    DEFINE(VCPU_IRQ_LINES,	offsetof(struct kvm_vcpu, arch.irq_lines));
>>    DEFINE(VCPU_HOST_CONTEXT,	offsetof(struct kvm_vcpu, arch.host_cpu_context));
>>    DEFINE(VCPU_TIMER_CNTV_CTL,	offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
>> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
>> index 34b8bd0..28dc92b 100644
>> --- a/arch/arm64/kvm/handle_exit.c
>> +++ b/arch/arm64/kvm/handle_exit.c
>> @@ -71,6 +71,26 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>>  	return 1;
>>  }
>>  
>> +/**
>> + * kvm_handle_bkpt - handle a break-point instruction
>> + *
>> + * @vcpu:	the vcpu pointer
>> + *
>> + * By definition if we arrive here it's because we are routing
>> + * all SW breakpoints to the hyper-visor as some may be a result of
>
> s/hyper-visor/hypervisor/
>
> this sentence is weird. I think what you want is a full stop after
> hypervisor and then a new sentence: Userspace may decide that this
> particular breakpoint should be routed to the guest (if the breakpoint
> does not come form userspace but by someone debugging a process inside
> the guest), and in that case inject a software breakpoint instruction by
> <insert the method here>.
>
>
>
>> + * guest debugging. If user-space decides this particular break-point
>> + * isn't for the host to handle it can re-feed the exception to the
>> + * guest.
>> + */
>> +static int kvm_handle_bkpt(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> +{
>> +	run->exit_reason = KVM_EXIT_DEBUG;
>> +	run->debug.arch.exit_type = KVM_DEBUG_EXIT_SW_BKPT;
>> +	run->debug.arch.address = *vcpu_pc(vcpu);
>> +	kvm_info("exiting from %llx\n", run->debug.arch.address);
>> +	return 0;
>> +}
>> +
>>  static exit_handle_fn arm_exit_handlers[] = {
>>  	[ESR_EL2_EC_WFI]	= kvm_handle_wfx,
>>  	[ESR_EL2_EC_CP15_32]	= kvm_handle_cp15_32,
>> @@ -85,6 +105,8 @@ static exit_handle_fn arm_exit_handlers[] = {
>>  	[ESR_EL2_EC_SYS64]	= kvm_handle_sys_reg,
>>  	[ESR_EL2_EC_IABT]	= kvm_handle_guest_abort,
>>  	[ESR_EL2_EC_DABT]	= kvm_handle_guest_abort,
>> +	[ESR_EL2_EC_BKPT32]	= kvm_handle_bkpt,
>> +	[ESR_EL2_EC_BRK64]	= kvm_handle_bkpt,
>>  };
>>  
>>  static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
>> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
>> index b72aa9f..3c733ea 100644
>> --- a/arch/arm64/kvm/hyp.S
>> +++ b/arch/arm64/kvm/hyp.S
>> @@ -772,6 +772,10 @@
>>  	orr	x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
>>  	orr	x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
>>  
>> +	// Any other bits (currently TDE)
>> +	ldr	x3, [x0, #VCPU_MDCR_EL2]
>> +	orr	x2, x2, x3
>> +
>>  	// Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap
>>  	// if not dirty.
>>  	ldr	x3, [x0, #VCPU_DEBUG_FLAGS]
>> -- 
>> 2.1.3
>> 
>
> It may be simpler to just load/restore the MDCR_EL2 and do all
> bit-manipulations for a specific VCPU in C-code instead of this.
>
> -Christoffer
diff mbox

Patch

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 2c6386e..9383359 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2592,7 +2592,7 @@  when running. Common control bits are:
 The top 16 bits of the control field are architecture specific control
 flags which can include the following:
 
-  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86]
+  - KVM_GUESTDBG_USE_SW_BP:     using software breakpoints [x86, arm64]
   - KVM_GUESTDBG_USE_HW_BP:     using hardware breakpoints [x86, s390]
   - KVM_GUESTDBG_INJECT_DB:     inject DB type exception [x86]
   - KVM_GUESTDBG_INJECT_BP:     inject BP type exception [x86]
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index a0ff410..48d26bb 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -303,6 +303,9 @@  void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 					struct kvm_guest_debug *dbg)
 {
+	/* Route debug traps to el2? */
+	bool route_el2 = false;
+
 	/* If it's not enabled clear all flags */
 	if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
 		vcpu->guest_debug = 0;
@@ -320,8 +323,8 @@  int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 
 	/* Software Break Points */
 	if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
-		kvm_info("SW BP support requested, not yet implemented\n");
-		return -EINVAL;
+		kvm_info("SW BP support requested\n");
+		route_el2 = true;
 	}
 
 	/* Hardware assisted Break and Watch points */
@@ -330,6 +333,20 @@  int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 		return -EINVAL;
 	}
 
+	/* If we are going to handle any debug exceptions we need to
+	 * set MDCE_EL2.TDE to ensure they are routed to the
+	 * hypervisor. If userspace determines the exception was
+	 * actually internal to the guest it needs to handle
+	 * re-injecting the exception.
+	 */
+	if (route_el2) {
+		kvm_info("routing debug exceptions");
+		vcpu->arch.mdcr_el2 = MDCR_EL2_TDE;
+	} else {
+		kvm_info("not routing debug exceptions");
+		vcpu->arch.mdcr_el2 = 0;
+	}
+
 	return 0;
 }
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2012c4b..38b0f07 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -98,6 +98,7 @@  struct kvm_vcpu_arch {
 
 	/* HYP configuration */
 	u64 hcr_el2;
+	u32 mdcr_el2;
 
 	/* Exception Information */
 	struct kvm_vcpu_fault_info fault;
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 9a9fce0..8da1043 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -122,6 +122,7 @@  int main(void)
   DEFINE(VCPU_HPFAR_EL2,	offsetof(struct kvm_vcpu, arch.fault.hpfar_el2));
   DEFINE(VCPU_DEBUG_FLAGS,	offsetof(struct kvm_vcpu, arch.debug_flags));
   DEFINE(VCPU_HCR_EL2,		offsetof(struct kvm_vcpu, arch.hcr_el2));
+  DEFINE(VCPU_MDCR_EL2,	offsetof(struct kvm_vcpu, arch.mdcr_el2));
   DEFINE(VCPU_IRQ_LINES,	offsetof(struct kvm_vcpu, arch.irq_lines));
   DEFINE(VCPU_HOST_CONTEXT,	offsetof(struct kvm_vcpu, arch.host_cpu_context));
   DEFINE(VCPU_TIMER_CNTV_CTL,	offsetof(struct kvm_vcpu, arch.timer_cpu.cntv_ctl));
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 34b8bd0..28dc92b 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -71,6 +71,26 @@  static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	return 1;
 }
 
+/**
+ * kvm_handle_bkpt - handle a break-point instruction
+ *
+ * @vcpu:	the vcpu pointer
+ *
+ * By definition if we arrive here it's because we are routing
+ * all SW breakpoints to the hyper-visor as some may be a result of
+ * guest debugging. If user-space decides this particular break-point
+ * isn't for the host to handle it can re-feed the exception to the
+ * guest.
+ */
+static int kvm_handle_bkpt(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+	run->exit_reason = KVM_EXIT_DEBUG;
+	run->debug.arch.exit_type = KVM_DEBUG_EXIT_SW_BKPT;
+	run->debug.arch.address = *vcpu_pc(vcpu);
+	kvm_info("exiting from %llx\n", run->debug.arch.address);
+	return 0;
+}
+
 static exit_handle_fn arm_exit_handlers[] = {
 	[ESR_EL2_EC_WFI]	= kvm_handle_wfx,
 	[ESR_EL2_EC_CP15_32]	= kvm_handle_cp15_32,
@@ -85,6 +105,8 @@  static exit_handle_fn arm_exit_handlers[] = {
 	[ESR_EL2_EC_SYS64]	= kvm_handle_sys_reg,
 	[ESR_EL2_EC_IABT]	= kvm_handle_guest_abort,
 	[ESR_EL2_EC_DABT]	= kvm_handle_guest_abort,
+	[ESR_EL2_EC_BKPT32]	= kvm_handle_bkpt,
+	[ESR_EL2_EC_BRK64]	= kvm_handle_bkpt,
 };
 
 static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index b72aa9f..3c733ea 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -772,6 +772,10 @@ 
 	orr	x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
 	orr	x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
 
+	// Any other bits (currently TDE)
+	ldr	x3, [x0, #VCPU_MDCR_EL2]
+	orr	x2, x2, x3
+
 	// Check for KVM_ARM64_DEBUG_DIRTY, and set debug to trap
 	// if not dirty.
 	ldr	x3, [x0, #VCPU_DEBUG_FLAGS]