Re: [Qemu-devel] [PATCH 4/5 v3][RESEND] ppc: Add software breakpoint support

[Madhavan Srinivasan <maddy@linux.vnet.ibm.com>]

On Tuesday 24 June 2014 10:36 PM, Bharat.Bhushan@freescale.com wrote:
> 
> 
>> -----Original Message-----
>> From: Madhavan Srinivasan [mailto:maddy@linux.vnet.ibm.com]
>> Sent: Tuesday, June 24, 2014 8:59 PM
>> To: Bhushan Bharat-R65777; agraf@suse.de
>> Cc: qemu-ppc@nongnu.org; qemu-devel@nongnu.org
>> Subject: Re: [PATCH 4/5 v3][RESEND] ppc: Add software breakpoint support
>>
>> On Tuesday 24 June 2014 05:40 PM, Bharat Bhushan wrote:
>>> This patch allow insert/remove software breakpoint
>>>
>>> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com>
>>> ---
>>>  target-ppc/kvm.c | 71
>>> +++++++++++++++++++++++++++++++++++++++++++++-----------
>>>  1 file changed, 57 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c index
>>> 5238de7..8e2dbb3 100644
>>> --- a/target-ppc/kvm.c
>>> +++ b/target-ppc/kvm.c
>>> @@ -1317,6 +1317,53 @@ static int kvmppc_handle_dcr_write(CPUPPCState *env,
>> uint32_t dcrn, uint32_t dat
>>>      return 0;
>>>  }
>>>
>>> +int kvm_arch_insert_sw_breakpoint(CPUState *cs, struct
>>> +kvm_sw_breakpoint *bp) {
>>> +    /* Mixed endian case is not handled */
>>> +    uint32_t sc = debug_inst_opcode;
>>> +
>>> +    if (cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 4, 0) ||
>>> +        cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&sc, 4, 1)) {
>>
>> Instead of hard coding, can we use sizeof ()?
> 
> Yes
> 
>>
>>> +        return -EINVAL;
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +int kvm_arch_remove_sw_breakpoint(CPUState *cs, struct
>>> +kvm_sw_breakpoint *bp) {
>>> +    uint32_t sc;
>>> +
>>> +    if (cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&sc, 4, 0) ||
>>> +        sc != debug_inst_opcode ||
>>> +        cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 4, 1)) {
>>> +        return -EINVAL;
>>> +    }
>>> +
>>
>> Same. Can we use sizeof?
> 
> Yes
> 
>>
>>> +    return 0;
>>> +}
>>> +
>>> +void kvm_arch_update_guest_debug(CPUState *cs, struct kvm_guest_debug
>>> +*dbg) {
>>> +    /* Software Breakpoint updates */
>>> +    if (kvm_sw_breakpoints_active(cs)) {
>>> +        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
>>> +    }
>>> +}
>>> +
>>> +static int kvm_handle_debug(PowerPCCPU *cpu, struct kvm_run *run) {
>>> +    CPUState *cs = CPU(cpu);
>>> +    struct kvm_debug_exit_arch *arch_info = &run->debug.arch;
>>> +    int handle = 0;
>>> +
>>> +    if (kvm_find_sw_breakpoint(cs, arch_info->address)) {
>>> +        handle = 1;
>>> +    }
>>> +
>>> +    return handle;
>>> +}
>>> +
>>>  int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)  {
>>>      PowerPCCPU *cpu = POWERPC_CPU(cs); @@ -1357,6 +1404,16 @@ int
>>> kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
>>>          ret = 0;
>>>          break;
>>>
>>> +    case KVM_EXIT_DEBUG:
>>> +        DPRINTF("handle debug exception\n");
>>> +        if (kvm_handle_debug(cpu, run)) {
>>> +            ret = EXCP_DEBUG;
>>> +            break;
>>> +        }
>>> +        /* re-enter, this exception was guest-internal */
>>
>> Kindly can you explain when this will happen?
> 
> If the debug interrupt condition (breakpoint/watchpoint etc) is not set by qemu, i.e that is set by guest. 
> 

OK. This is my understanding. Kindly correct if it is wrong.
If we are here without any breakpoint from qemu, are we not suppose to
pass it on to guest with an interrupt inject?

Also, can we make it as if-else with single break for KVM_EXIT_DEBUG case.

Regards
Maddy

> Thanks
> -Bharat
> 
>>
>>> +        ret = 0;
>>> +        break;
>>> +
>>>      default:
>>>          fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
>>>          ret = -1;
>>> @@ -2044,16 +2101,6 @@ void kvm_arch_init_irq_routing(KVMState *s)  {
>>> }
>>>
>>> -int kvm_arch_insert_sw_breakpoint(CPUState *cpu, struct
>>> kvm_sw_breakpoint *bp) -{
>>> -    return -EINVAL;
>>> -}
>>> -
>>> -int kvm_arch_remove_sw_breakpoint(CPUState *cpu, struct
>>> kvm_sw_breakpoint *bp) -{
>>> -    return -EINVAL;
>>> -}
>>> -
>>>  int kvm_arch_insert_hw_breakpoint(target_ulong addr, target_ulong
>>> len, int type)  {
>>>      return -EINVAL;
>>> @@ -2068,10 +2115,6 @@ void kvm_arch_remove_all_hw_breakpoints(void)
>>>  {
>>>  }
>>>
>>> -void kvm_arch_update_guest_debug(CPUState *cpu, struct
>>> kvm_guest_debug *dbg) -{ -}
>>> -
>>>  struct kvm_get_htab_buf {
>>>      struct kvm_get_htab_header header;
>>>      /*
>>>
>