Until now, when we connect gdb to the QEMU gdb-server, the
single-step mode is not managed.
This patch adds this, only for kvm-pr:
If KVM_GUESTDBG_SINGLESTEP is set, we enable single-step trace bit in the
MSR (MSR_SE) just before the __kvmppc_vcpu_run(), and disable it just after.
In kvmppc_handle_exit_pr, instead of routing the interrupt to
the guest, we return to host, with KVM_EXIT_DEBUG reason.
Signed-off-by: Laurent Vivier <[email protected]>
---
arch/powerpc/kvm/book3s_pr.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 95bceca..e6896f4 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -882,6 +882,24 @@ void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr)
}
#endif
+static void kvmppc_setup_debug(struct kvm_vcpu *vcpu)
+{
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+ u64 msr = kvmppc_get_msr(vcpu);
+
+ kvmppc_set_msr(vcpu, msr | MSR_SE);
+ }
+}
+
+static void kvmppc_clear_debug(struct kvm_vcpu *vcpu)
+{
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+ u64 msr = kvmppc_get_msr(vcpu);
+
+ kvmppc_set_msr(vcpu, msr & ~MSR_SE);
+ }
+}
+
int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
unsigned int exit_nr)
{
@@ -1208,8 +1226,13 @@ program_interrupt:
#endif
case BOOK3S_INTERRUPT_MACHINE_CHECK:
case BOOK3S_INTERRUPT_TRACE:
- kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
- r = RESUME_GUEST;
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+ run->exit_reason = KVM_EXIT_DEBUG;
+ r = RESUME_HOST;
+ } else {
+ kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
+ r = RESUME_GUEST;
+ }
break;
default:
{
@@ -1479,6 +1502,8 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
goto out;
}
+ kvmppc_setup_debug(vcpu);
+
/*
* Interrupts could be timers for the guest which we have to inject
* again, so let's postpone them until we're in the guest and if we
@@ -1501,6 +1526,8 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
ret = __kvmppc_vcpu_run(kvm_run, vcpu);
+ kvmppc_clear_debug(vcpu);
+
/* No need for kvm_guest_exit. It's done in handle_exit.
We also get here with interrupts enabled. */
--
2.5.0
Ping?
On 22/03/2016 15:53, Laurent Vivier wrote:
> Until now, when we connect gdb to the QEMU gdb-server, the
> single-step mode is not managed.
>
> This patch adds this, only for kvm-pr:
>
> If KVM_GUESTDBG_SINGLESTEP is set, we enable single-step trace bit in the
> MSR (MSR_SE) just before the __kvmppc_vcpu_run(), and disable it just after.
> In kvmppc_handle_exit_pr, instead of routing the interrupt to
> the guest, we return to host, with KVM_EXIT_DEBUG reason.
>
> Signed-off-by: Laurent Vivier <[email protected]>
> ---
> arch/powerpc/kvm/book3s_pr.c | 31 +++++++++++++++++++++++++++++--
> 1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 95bceca..e6896f4 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -882,6 +882,24 @@ void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr)
> }
> #endif
>
> +static void kvmppc_setup_debug(struct kvm_vcpu *vcpu)
> +{
> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> + u64 msr = kvmppc_get_msr(vcpu);
> +
> + kvmppc_set_msr(vcpu, msr | MSR_SE);
> + }
> +}
> +
> +static void kvmppc_clear_debug(struct kvm_vcpu *vcpu)
> +{
> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> + u64 msr = kvmppc_get_msr(vcpu);
> +
> + kvmppc_set_msr(vcpu, msr & ~MSR_SE);
> + }
> +}
> +
> int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
> unsigned int exit_nr)
> {
> @@ -1208,8 +1226,13 @@ program_interrupt:
> #endif
> case BOOK3S_INTERRUPT_MACHINE_CHECK:
> case BOOK3S_INTERRUPT_TRACE:
> - kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
> - r = RESUME_GUEST;
> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> + run->exit_reason = KVM_EXIT_DEBUG;
> + r = RESUME_HOST;
> + } else {
> + kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
> + r = RESUME_GUEST;
> + }
> break;
> default:
> {
> @@ -1479,6 +1502,8 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> goto out;
> }
>
> + kvmppc_setup_debug(vcpu);
> +
> /*
> * Interrupts could be timers for the guest which we have to inject
> * again, so let's postpone them until we're in the guest and if we
> @@ -1501,6 +1526,8 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
>
> ret = __kvmppc_vcpu_run(kvm_run, vcpu);
>
> + kvmppc_clear_debug(vcpu);
> +
> /* No need for kvm_guest_exit. It's done in handle_exit.
> We also get here with interrupts enabled. */
>
>
On 22.03.2016 15:53, Laurent Vivier wrote:
> Until now, when we connect gdb to the QEMU gdb-server, the
> single-step mode is not managed.
>
> This patch adds this, only for kvm-pr:
>
> If KVM_GUESTDBG_SINGLESTEP is set, we enable single-step trace bit in the
> MSR (MSR_SE) just before the __kvmppc_vcpu_run(), and disable it just after.
> In kvmppc_handle_exit_pr, instead of routing the interrupt to
> the guest, we return to host, with KVM_EXIT_DEBUG reason.
>
> Signed-off-by: Laurent Vivier <[email protected]>
> ---
> arch/powerpc/kvm/book3s_pr.c | 31 +++++++++++++++++++++++++++++--
> 1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index 95bceca..e6896f4 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -882,6 +882,24 @@ void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr)
> }
> #endif
>
> +static void kvmppc_setup_debug(struct kvm_vcpu *vcpu)
> +{
> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> + u64 msr = kvmppc_get_msr(vcpu);
> +
> + kvmppc_set_msr(vcpu, msr | MSR_SE);
> + }
> +}
> +
> +static void kvmppc_clear_debug(struct kvm_vcpu *vcpu)
> +{
> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> + u64 msr = kvmppc_get_msr(vcpu);
> +
> + kvmppc_set_msr(vcpu, msr & ~MSR_SE);
> + }
> +}
> +
> int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
> unsigned int exit_nr)
> {
> @@ -1208,8 +1226,13 @@ program_interrupt:
> #endif
> case BOOK3S_INTERRUPT_MACHINE_CHECK:
> case BOOK3S_INTERRUPT_TRACE:
> - kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
> - r = RESUME_GUEST;
> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> + run->exit_reason = KVM_EXIT_DEBUG;
> + r = RESUME_HOST;
> + } else {
> + kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
> + r = RESUME_GUEST;
> + }
Should the new code rather be limited to the BOOK3S_INTERRUPT_TRACE case
only? I mean, this way, you never can deliver a machine check interrupt
to the guest if singlestep debugging is enabled on the host, can you?
Thomas
On 08/04/2016 08:23, Thomas Huth wrote:
> On 22.03.2016 15:53, Laurent Vivier wrote:
>> Until now, when we connect gdb to the QEMU gdb-server, the
>> single-step mode is not managed.
>>
>> This patch adds this, only for kvm-pr:
>>
>> If KVM_GUESTDBG_SINGLESTEP is set, we enable single-step trace bit in the
>> MSR (MSR_SE) just before the __kvmppc_vcpu_run(), and disable it just after.
>> In kvmppc_handle_exit_pr, instead of routing the interrupt to
>> the guest, we return to host, with KVM_EXIT_DEBUG reason.
>>
>> Signed-off-by: Laurent Vivier <[email protected]>
>> ---
>> arch/powerpc/kvm/book3s_pr.c | 31 +++++++++++++++++++++++++++++--
>> 1 file changed, 29 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
>> index 95bceca..e6896f4 100644
>> --- a/arch/powerpc/kvm/book3s_pr.c
>> +++ b/arch/powerpc/kvm/book3s_pr.c
>> @@ -882,6 +882,24 @@ void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr)
>> }
>> #endif
>>
>> +static void kvmppc_setup_debug(struct kvm_vcpu *vcpu)
>> +{
>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>> + u64 msr = kvmppc_get_msr(vcpu);
>> +
>> + kvmppc_set_msr(vcpu, msr | MSR_SE);
>> + }
>> +}
>> +
>> +static void kvmppc_clear_debug(struct kvm_vcpu *vcpu)
>> +{
>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>> + u64 msr = kvmppc_get_msr(vcpu);
>> +
>> + kvmppc_set_msr(vcpu, msr & ~MSR_SE);
>> + }
>> +}
>> +
>> int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>> unsigned int exit_nr)
>> {
>> @@ -1208,8 +1226,13 @@ program_interrupt:
>> #endif
>> case BOOK3S_INTERRUPT_MACHINE_CHECK:
>> case BOOK3S_INTERRUPT_TRACE:
>> - kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
>> - r = RESUME_GUEST;
>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>> + run->exit_reason = KVM_EXIT_DEBUG;
>> + r = RESUME_HOST;
>> + } else {
>> + kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
>> + r = RESUME_GUEST;
>> + }
>
> Should the new code rather be limited to the BOOK3S_INTERRUPT_TRACE case
> only? I mean, this way, you never can deliver a machine check interrupt
> to the guest if singlestep debugging is enabled on the host, can you?
You're right but it adds complexity and it would be only useful to
single-step the single-step mode of the guest.
It's hard to imagine a developer single-stepping the guest kernel while
he is single-stepping a user application in the guest.
It's why I have completely by-passed this case.
Thanks,
Laurent
On 08.04.2016 08:58, Laurent Vivier wrote:
>
>
> On 08/04/2016 08:23, Thomas Huth wrote:
>> On 22.03.2016 15:53, Laurent Vivier wrote:
>>> Until now, when we connect gdb to the QEMU gdb-server, the
>>> single-step mode is not managed.
>>>
>>> This patch adds this, only for kvm-pr:
>>>
>>> If KVM_GUESTDBG_SINGLESTEP is set, we enable single-step trace bit in the
>>> MSR (MSR_SE) just before the __kvmppc_vcpu_run(), and disable it just after.
>>> In kvmppc_handle_exit_pr, instead of routing the interrupt to
>>> the guest, we return to host, with KVM_EXIT_DEBUG reason.
>>>
>>> Signed-off-by: Laurent Vivier <[email protected]>
>>> ---
>>> arch/powerpc/kvm/book3s_pr.c | 31 +++++++++++++++++++++++++++++--
>>> 1 file changed, 29 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
>>> index 95bceca..e6896f4 100644
>>> --- a/arch/powerpc/kvm/book3s_pr.c
>>> +++ b/arch/powerpc/kvm/book3s_pr.c
>>> @@ -882,6 +882,24 @@ void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr)
>>> }
>>> #endif
>>>
>>> +static void kvmppc_setup_debug(struct kvm_vcpu *vcpu)
>>> +{
>>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>>> + u64 msr = kvmppc_get_msr(vcpu);
>>> +
>>> + kvmppc_set_msr(vcpu, msr | MSR_SE);
>>> + }
>>> +}
>>> +
>>> +static void kvmppc_clear_debug(struct kvm_vcpu *vcpu)
>>> +{
>>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>>> + u64 msr = kvmppc_get_msr(vcpu);
>>> +
>>> + kvmppc_set_msr(vcpu, msr & ~MSR_SE);
>>> + }
>>> +}
>>> +
>>> int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>> unsigned int exit_nr)
>>> {
>>> @@ -1208,8 +1226,13 @@ program_interrupt:
>>> #endif
>>> case BOOK3S_INTERRUPT_MACHINE_CHECK:
>>> case BOOK3S_INTERRUPT_TRACE:
>>> - kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
>>> - r = RESUME_GUEST;
>>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>>> + run->exit_reason = KVM_EXIT_DEBUG;
>>> + r = RESUME_HOST;
>>> + } else {
>>> + kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
>>> + r = RESUME_GUEST;
>>> + }
>>
>> Should the new code rather be limited to the BOOK3S_INTERRUPT_TRACE case
>> only? I mean, this way, you never can deliver a machine check interrupt
>> to the guest if singlestep debugging is enabled on the host, can you?
>
> You're right but it adds complexity and it would be only useful to
> single-step the single-step mode of the guest.
>
> It's hard to imagine a developer single-stepping the guest kernel while
> he is single-stepping a user application in the guest.
Hmm, not sure whether you've got me right ;-) I rather meant: What
happens when a machine check is supposed to happen in the guest while
single stepping is enabled at the host level? IMHO it would be better to
shape the code like this:
case BOOK3S_INTERRUPT_MACHINE_CHECK:
kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
r = RESUME_GUEST;
break;
case BOOK3S_INTERRUPT_TRACE:
if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
run->exit_reason = KVM_EXIT_DEBUG;
r = RESUME_HOST;
} else {
kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
r = RESUME_GUEST;
}
That means, split the two cases, to keep the old behavior for the
MACHINE_CHECK case. That's also not too much of additional complexity,
is it?
Thomas
On 08/04/2016 09:44, Thomas Huth wrote:
> On 08.04.2016 08:58, Laurent Vivier wrote:
>>
>>
>> On 08/04/2016 08:23, Thomas Huth wrote:
>>> On 22.03.2016 15:53, Laurent Vivier wrote:
>>>> Until now, when we connect gdb to the QEMU gdb-server, the
>>>> single-step mode is not managed.
>>>>
>>>> This patch adds this, only for kvm-pr:
>>>>
>>>> If KVM_GUESTDBG_SINGLESTEP is set, we enable single-step trace bit in the
>>>> MSR (MSR_SE) just before the __kvmppc_vcpu_run(), and disable it just after.
>>>> In kvmppc_handle_exit_pr, instead of routing the interrupt to
>>>> the guest, we return to host, with KVM_EXIT_DEBUG reason.
>>>>
>>>> Signed-off-by: Laurent Vivier <[email protected]>
>>>> ---
>>>> arch/powerpc/kvm/book3s_pr.c | 31 +++++++++++++++++++++++++++++--
>>>> 1 file changed, 29 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
>>>> index 95bceca..e6896f4 100644
>>>> --- a/arch/powerpc/kvm/book3s_pr.c
>>>> +++ b/arch/powerpc/kvm/book3s_pr.c
>>>> @@ -882,6 +882,24 @@ void kvmppc_set_fscr(struct kvm_vcpu *vcpu, u64 fscr)
>>>> }
>>>> #endif
>>>>
>>>> +static void kvmppc_setup_debug(struct kvm_vcpu *vcpu)
>>>> +{
>>>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>>>> + u64 msr = kvmppc_get_msr(vcpu);
>>>> +
>>>> + kvmppc_set_msr(vcpu, msr | MSR_SE);
>>>> + }
>>>> +}
>>>> +
>>>> +static void kvmppc_clear_debug(struct kvm_vcpu *vcpu)
>>>> +{
>>>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>>>> + u64 msr = kvmppc_get_msr(vcpu);
>>>> +
>>>> + kvmppc_set_msr(vcpu, msr & ~MSR_SE);
>>>> + }
>>>> +}
>>>> +
>>>> int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>>> unsigned int exit_nr)
>>>> {
>>>> @@ -1208,8 +1226,13 @@ program_interrupt:
>>>> #endif
>>>> case BOOK3S_INTERRUPT_MACHINE_CHECK:
>>>> case BOOK3S_INTERRUPT_TRACE:
>>>> - kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
>>>> - r = RESUME_GUEST;
>>>> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
>>>> + run->exit_reason = KVM_EXIT_DEBUG;
>>>> + r = RESUME_HOST;
>>>> + } else {
>>>> + kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
>>>> + r = RESUME_GUEST;
>>>> + }
>>>
>>> Should the new code rather be limited to the BOOK3S_INTERRUPT_TRACE case
>>> only? I mean, this way, you never can deliver a machine check interrupt
>>> to the guest if singlestep debugging is enabled on the host, can you?
>>
>> You're right but it adds complexity and it would be only useful to
>> single-step the single-step mode of the guest.
>>
>> It's hard to imagine a developer single-stepping the guest kernel while
>> he is single-stepping a user application in the guest.
>
> Hmm, not sure whether you've got me right ;-) I rather meant: What
Yes, I've missed what you mean. :(
Thank you to try again :)
> happens when a machine check is supposed to happen in the guest while
> single stepping is enabled at the host level? IMHO it would be better to
> shape the code like this:
>
> case BOOK3S_INTERRUPT_MACHINE_CHECK:
> kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
> r = RESUME_GUEST;
> break;
> case BOOK3S_INTERRUPT_TRACE:
> if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> run->exit_reason = KVM_EXIT_DEBUG;
> r = RESUME_HOST;
> } else {
> kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
> r = RESUME_GUEST;
> }
>
> That means, split the two cases, to keep the old behavior for the
> MACHINE_CHECK case. That's also not too much of additional complexity,
> is it?
Yes, you're right.
Thanks,
Laurent