[PATCH v4] powerpc/kvm: support to handle sw breakpoint

[Alexander Graf]

> Am 23.08.2014 um 12:17 schrieb Madhavan Srinivasan <maddy at linux.vnet.ibm.com>:
> 
>> On Thursday 21 August 2014 02:40 PM, Alexander Graf wrote:
>> 
>> 
>>> On 20.08.14 07:52, Madhavan Srinivasan wrote:
>>> This patch adds kernel side support for software breakpoint.
>>> Design is that, by using an illegal instruction, we trap to hypervisor
>>> via Emulation Assistance interrupt, where we check for the illegal instruction
>>> and accordingly we return to Host or Guest. Patch also adds support for
>>> software breakpoint in PR KVM.
>>> 
>>> Changes v3->v4:
>>> Made changes to code comments and removed #define of zero opcode
>>> Added a new function to handle the debug instruction emulation in book3s_hv
>>> Rebased the code to latest upstream source.
>>> 
>>> Changes v2->v3:
>>> Changed the debug instructions. Using the all zero opcode in the instruction word
>>>  as illegal instruction as mentioned in Power ISA instead of ABS
>>> Removed reg updated in emulation assist and added a call to
>>>  kvmppc_emulate_instruction for reg update.
>>> 
>>> Changes v1->v2:
>>> 
>>> Moved the debug instruction #def to kvm_book3s.h. This way PR_KVM can also share it.
>>> Added code to use KVM get one reg infrastructure to get debug opcode.
>>> Updated emulate.c to include emulation of debug instruction incase of PR_KVM.
>>> Made changes to commit message.
>>> 
>>> Signed-off-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>
>>> ---
>>> arch/powerpc/include/asm/kvm_book3s.h |  7 +++++++
>>> arch/powerpc/kvm/book3s.c             |  3 ++-
>>> arch/powerpc/kvm/book3s_hv.c          | 32 ++++++++++++++++++++++++++++++--
>>> arch/powerpc/kvm/book3s_pr.c          |  3 +++
>>> arch/powerpc/kvm/emulate.c            | 11 +++++++++++
>>> 5 files changed, 53 insertions(+), 3 deletions(-)
>>> 
>>> diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
>>> index 6acf0c2..a1944f8 100644
>>> --- a/arch/powerpc/include/asm/kvm_book3s.h
>>> +++ b/arch/powerpc/include/asm/kvm_book3s.h
>>> @@ -24,6 +24,13 @@
>>> #include <linux/kvm_host.h>
>>> #include <asm/kvm_book3s_asm.h>
>>> 
>>> +/*
>>> + * KVMPPC_INST_BOOK3S_DEBUG is debug Instruction for supporting Software Breakpoint.
>>> + * Based on PowerISA v2.07, Instruction with primary opcode 0 will be treated as illegal
>>> + * instruction.
>>> + */
>>> +#define KVMPPC_INST_BOOK3S_DEBUG    0x00dddd00
>> 
>> Please change the BookE version of this as well, put the define in a
>> common header and use a non book specific name.
> 
> I first wanted to get the server side in and then take up this, but i
> can do it with this, just concerned incase of booke testing :(

I can test, no problem. You can at least do compile tests on your side already ;)

> 
>>> +
>>> struct kvmppc_bat {
>>>    u64 raw;
>>>    u32 bepi;
>>> diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
>>> index dd03f6b..00e9c9f 100644
>>> --- a/arch/powerpc/kvm/book3s.c
>>> +++ b/arch/powerpc/kvm/book3s.c
>>> @@ -778,7 +778,8 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
>>> int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>>>                    struct kvm_guest_debug *dbg)
>>> {
>>> -    return -EINVAL;
>>> +    vcpu->guest_debug = dbg->control;
>>> +    return 0;
>>> }
>>> 
>>> void kvmppc_decrementer_func(unsigned long data)
>>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>>> index 27cced9..0a92e45 100644
>>> --- a/arch/powerpc/kvm/book3s_hv.c
>>> +++ b/arch/powerpc/kvm/book3s_hv.c
>>> @@ -725,6 +725,14 @@ static int kvmppc_hcall_impl_hv(unsigned long cmd)
>>>    return kvmppc_hcall_impl_hv_realmode(cmd);
>>> }
>>> 
>>> +static int kvmppc_emulate_debug_instruction_hv(struct kvm_run *run,
>>> +                    struct kvm_vcpu *vcpu)
>>> +{
>>> +    run->exit_reason = KVM_EXIT_DEBUG;
>>> +    run->debug.arch.address = kvmppc_get_pc(vcpu);
>>> +    return 0;
>>> +}
>>> +
>>> static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>>                 struct task_struct *tsk)
>>> {
>>> @@ -811,9 +819,26 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>>     * we don't emulate any guest instructions at this stage.
>> 
>> This comment is no longer true, it should get changed.
> 
> Will change it.
> 
>>>     */
>>>    case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
>>> -        kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>>> -        r = RESUME_GUEST;
>>> +    {
>>> +        u32 last_inst;
>>> +        if(kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=
>>> +                    EMULATE_DONE) {
>> 
>> Please only do this if debugging is active.
> 
> Ok sure. But i will add in the else part of the check. Since we do the
> instruction check there.

We should only fetch the instruction if sw breakpoint debugging is active.

Alex