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.
>> +
>> 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) ?
Thanks for review
Regards
Maddy
>
> Alex
>
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