On Friday 04 July 2014 12:18 PM, Alexander Graf wrote:
>
> On 04.07.14 06:34, Madhavan Srinivasan wrote:
>> On Thursday 03 July 2014 05:21 PM, Alexander Graf wrote:
>>> On 01.07.14 10:41, 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.
>>>>
>>>> Patch mandates use of "abs" instruction as sw breakpoint instruction
>>>> (primary opcode 31 and extended opcode 360). Based on PowerISA v2.01,
>>>> ABS instruction has been dropped from the architecture and treated an
>>>> illegal instruction.
>>>>
>>>> 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@xxxxxxxxxxxxxxxxxx>
>>>> ---
>>>> arch/powerpc/include/asm/kvm_book3s.h | 8 ++++++++
>>>> arch/powerpc/include/asm/ppc-opcode.h | 5 +++++
>>>> arch/powerpc/kvm/book3s.c | 3 ++-
>>>> arch/powerpc/kvm/book3s_hv.c | 9 +++++++++
>>>> arch/powerpc/kvm/book3s_pr.c | 3 +++
>>>> arch/powerpc/kvm/emulate.c | 10 ++++++++++
>>>> 6 files changed, 37 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/powerpc/include/asm/kvm_book3s.h
>>>> b/arch/powerpc/include/asm/kvm_book3s.h
>>>> index f52f656..180d549 100644
>>>> --- a/arch/powerpc/include/asm/kvm_book3s.h
>>>> +++ b/arch/powerpc/include/asm/kvm_book3s.h
>>>> @@ -24,6 +24,14 @@
>>>> #include <linux/kvm_host.h>
>>>> #include <asm/kvm_book3s_asm.h>
>>>> +/*
>>>> + * KVMPPC_INST_BOOK3S_DEBUG is debug Instruction for supporting
>>>> Software Breakpoint.
>>>> + * Instruction mnemonic is ABS, primary opcode is 31 and extended
>>>> opcode is 360.
>>>> + * Based on PowerISA v2.01, ABS instruction has been dropped from the
>>>> architecture
>>>> + * and treated an illegal instruction.
>>>> + */
>>>> +#define KVMPPC_INST_BOOK3S_DEBUG 0x7c0002d0
>>> This will still break with LE guests.
>>>
>> I am told to try with all 0s opcode. So rewriting the patch.
>
> The problem with "all 0s" is that it's reasonably likely to occur on
> real world code. Hence Segher was proposing something like 0x00dddd00
> which should be the same regardless of endianness, but has a certain
> appeal of intentional placement ;).
>
Ok Sure.
>>
>>>> +
>>>> struct kvmppc_bat {
>>>> u64 raw;
>>>> u32 bepi;
>>>> diff --git a/arch/powerpc/include/asm/ppc-opcode.h
>>>> b/arch/powerpc/include/asm/ppc-opcode.h
>>>> index 3132bb9..3fbb4c1 100644
>>>> --- a/arch/powerpc/include/asm/ppc-opcode.h
>>>> +++ b/arch/powerpc/include/asm/ppc-opcode.h
>>>> @@ -111,6 +111,11 @@
>>>> #define OP_31_XOP_LHBRX 790
>>>> #define OP_31_XOP_STHBRX 918
>>>> +/* KVMPPC_INST_BOOK3S_DEBUG -- Software breakpoint Instruction
>>>> + * Instruction mnemonic is ABS, primary opcode is 31 and extended
>>>> opcode is 360.
>>>> + */
>>>> +#define OP_31_XOP_ABS 360
>>>> +
>>>> #define OP_LWZ 32
>>>> #define OP_LD 58
>>>> #define OP_LWZU 33
>>>> diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
>>>> index c254c27..b40fe5d 100644
>>>> --- a/arch/powerpc/kvm/book3s.c
>>>> +++ b/arch/powerpc/kvm/book3s.c
>>>> @@ -789,7 +789,8 @@ 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 7a12edb..402c1ec 100644
>>>> --- a/arch/powerpc/kvm/book3s_hv.c
>>>> +++ b/arch/powerpc/kvm/book3s_hv.c
>>>> @@ -725,8 +725,14 @@ static int kvmppc_handle_exit_hv(struct kvm_run
>>>> *run, struct kvm_vcpu *vcpu,
>>>> * we don't emulate any guest instructions at this stage.
>>>> */
>>>> case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
>>>> + if (kvmppc_get_last_inst(vcpu) == KVMPPC_INST_BOOK3S_DEBUG ) {
>>>> + run->exit_reason = KVM_EXIT_DEBUG;
>>>> + run->debug.arch.address = kvmppc_get_pc(vcpu);
>>>> + r = RESUME_HOST;
>>> Phew - why can't we just go into the normal instruction emulator for
>>> EMUL_ASSIST?
>>>
>> IIUC, using the emulation_assist_interrupt function (kernel/trap.c) ?
>
> I was more thinking of kvmppc_emulate_instruction() :).
>
This makes sense. Can use the same call for pr kvm also. awesome :)
>
> Alex
>
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