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@xxxxxxxxxxxxxxxxxx>
> ---
> 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.
> +
> 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.
> */
> 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.
> + /*
> + * 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.
Alex
> + run->debug.arch.address = kvmppc_get_pc(vcpu);
> + emulated = EMULATE_EXIT_USER;
> + advance = 0;
> + break;
> +
> default:
> emulated = EMULATE_FAIL;
> }
>
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