Re: [PATCH 1/2 v5] powerpc/kvm: support to handle sw breakpoint

Madhavan Srinivasan
2014-09-09T07:31:00Z

On Monday 08 September 2014 06:35 PM, Alexander Graf wrote:
>
>
> On 07.09.14 18:31, 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.
>>
>> Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/include/asm/kvm_ppc.h | 6 ++++++
>> arch/powerpc/kvm/book3s.c | 3 ++-
>> arch/powerpc/kvm/book3s_hv.c | 41 ++++++++++++++++++++++++++++++++++----
>> arch/powerpc/kvm/book3s_pr.c | 3 +++
>> arch/powerpc/kvm/emulate.c | 18 +++++++++++++++++
>> 5 files changed, 66 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
>> index fb86a22..dd83c9a 100644
>> --- a/arch/powerpc/include/asm/kvm_ppc.h
>> +++ b/arch/powerpc/include/asm/kvm_ppc.h
>> @@ -38,6 +38,12 @@
>> #include <asm/paca.h>
>> #endif
>>
>> +/*
>> + * KVMPPC_INST_SW_BREAKPOINT is debug Instruction
>> + * for supporting software breakpoint.
>> + */
>> +#define KVMPPC_INST_SW_BREAKPOINT 0x00dddd00
>> +
>> enum emulation_result {
>> EMULATE_DONE, /* no further processing */
>> EMULATE_DO_MMIO, /* kvm_run filled with MMIO request */
>> 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..3a2414c 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -725,6 +725,30 @@ static int kvmppc_hcall_impl_hv(unsigned long cmd)
>> return kvmppc_hcall_impl_hv_realmode(cmd);
>> }
>>
>> +static int kvmppc_emulate_debug_inst(struct kvm_run *run,
>> + struct kvm_vcpu *vcpu)
>> +{
>> + u32 last_inst;
>> +
>> + if(kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=
>> + EMULATE_DONE) {
>> + /*
>> + * Fetch failed, so return to guest and
>> + * try executing it again.
>> + */
>> + return RESUME_GUEST;
>
> Please end the if() here. In the kernel we usually treat abort
> situations as separate.
>

OK. Will change it.

>> + } else {
>> + if (last_inst == KVMPPC_INST_SW_BREAKPOINT) {
>> + run->exit_reason = KVM_EXIT_DEBUG;
>> + run->debug.arch.address = kvmppc_get_pc(vcpu);
>> + return RESUME_HOST;
>> + } else {
>> + kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> + return RESUME_GUEST;
>> + }
>> + }
>> +}
>> +
>> static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
>> struct task_struct *tsk)
>> {
>> @@ -807,12 +831,18 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
>> break;
>> /*
>> * This occurs if the guest executes an illegal instruction.
>> - * We just generate a program interrupt to the guest, since
>> - * we don't emulate any guest instructions at this stage.
>> + * If the guest debug is disabled, generate a program interrupt
>> + * to the guest. If guest debug is enabled, we need to check
>> + * whether the instruction is a software breakpoint instruction.
>> + * Accordingly return to Guest or Host.
>> */
>> case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
>> - kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> - r = RESUME_GUEST;
>> + if(vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
>> + r = kvmppc_emulate_debug_inst(run, vcpu);
>> + } else {
>> + kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> + r = RESUME_GUEST;
>> + }
>> break;
>> /*
>> * This occurs if the guest (kernel or userspace), does something that
>> @@ -922,6 +952,9 @@ static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
>> long int i;
>>
>> switch (id) {
>> + case KVM_REG_PPC_DEBUG_INST:
>> + *val = get_reg_val(id, KVMPPC_INST_SW_BREAKPOINT);
>> + break;
>> case KVM_REG_PPC_HIOR:
>> *val = get_reg_val(id, 0);
>> break;
>> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
>> index faffb27..6d73708 100644
>> --- a/arch/powerpc/kvm/book3s_pr.c
>> +++ b/arch/powerpc/kvm/book3s_pr.c
>> @@ -1319,6 +1319,9 @@ static int kvmppc_get_one_reg_pr(struct kvm_vcpu *vcpu, u64 id,
>> int r = 0;
>>
>> switch (id) {
>> + case KVM_REG_PPC_DEBUG_INST:
>> + *val = get_reg_val(id, KVMPPC_INST_SW_BREAKPOINT);
>> + break;
>> case KVM_REG_PPC_HIOR:
>> *val = get_reg_val(id, to_book3s(vcpu)->hior);
>> break;
>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>> index e96b50d..30f326b 100644
>> --- a/arch/powerpc/kvm/emulate.c
>> +++ b/arch/powerpc/kvm/emulate.c
>> @@ -274,6 +274,24 @@ int kvmppc_emulate_instruction(struct kvm_run *run, struct kvm_vcpu *vcpu)
>> }
>> break;
>>
>> + case 0:
>> + /*
>> + * Instruction with primary opcode 0. Based on PowerISA
>> + * these are illegal instructions.
>> + */
>> + if(inst == KVMPPC_INST_SW_BREAKPOINT) {
>
> Here you're missing a space between if and (. Are you sure that you ran
> checkpatch.pl?
>

No. my bad. Did not run checkpatch.pl. Will fix it.

>
>> + run->exit_reason = KVM_EXIT_DEBUG;
>> + run->debug.arch.address = kvmppc_get_pc(vcpu);
>> + emulated = EMULATE_EXIT_USER;
>> + advance = 0;
>> + printk(KERN_INFO "pr_emulate: debug instr \n");
>> + } else {
>> + kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> + emulated = EMULATE_DONE;
>> + advance = 0;
>
> Just set emulated = EMULATE_FAIL here, the same as default:.
>
>

Ok sure will do.

Thanks for review.
Maddy

> Alex
>
>> + }
>> + break;
>> +
>> default:
>> emulated = EMULATE_FAIL;
>> }
>>
>