[PATCH v4] powerpc/kvm: support to handle sw breakpoint
Madhavan Srinivasan
maddy at linux.vnet.ibm.com
Sat Aug 23 20:17:46 EST 2014
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 :(
>> +
>> 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.
>> + /*
>> + * Fetch failed, so return to guest and
>> + * try executing it again.
>> + */
>> + r = RESUME_GUEST;
>> + } else {
>> + if (last_inst == KVMPPC_INST_BOOK3S_DEBUG) {
>> + kvmppc_emulate_debug_instruction_hv(run, vcpu);
>> + r = RESUME_HOST;
>> + } else {
>> + kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
>> + r = RESUME_GUEST;
>> + }
>> + }
>> break;
>> + }
>> /*
>> * This occurs if the guest (kernel or userspace), does something that
>> * is prohibited by HFSCR. We just generate a program interrupt to
>> @@ -922,6 +947,9 @@ 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_BOOK3S_DEBUG);
>> + 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..cd2a39d 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_BOOK3S_DEBUG);
>> + 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..68f38b2 100644
>> --- a/arch/powerpc/kvm/emulate.c
>> +++ b/arch/powerpc/kvm/emulate.c
>> @@ -274,6 +274,17 @@ 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.
>> + */
>> + run->exit_reason = KVM_EXIT_DEBUG;
>
> This is wrong. We need to check that the instruction is 0x00dddd00. Any
> other op0 instruction should trigger an invalid instruction trap.
>
Ok.
Thanks for review
Regards
Maddy
>
> Alex
>
>> + run->debug.arch.address = kvmppc_get_pc(vcpu);
>> + emulated = EMULATE_EXIT_USER;
>> + advance = 0;
>> + break;
>> +
>> default:
>> emulated = EMULATE_FAIL;
>> }
>>
>
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