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Re: [Xen-devel] [PATCH v3 2/4] hvm/svm: Enable Breakpoint events



On Mon, Feb 12, 2018 at 8:08 AM, Alexandru Isaila
<aisaila@xxxxxxxxxxxxxxx> wrote:
> This commit implements the breakpoint events for svm.
> At the moment, the Breakpoint vmexit is not forwarded to the monitor layer.

This is a bit confusing as it sounds like as if you were saying that
after this patch the event is not forwarded when I think you mean that
before this patch it's not forwarded.

> This patch adds the hvm_monitor_debug call to the VMEXIT_EXCEPTION_BP.
> Also, the Software Breakpoint cap is moved from the Intel arch to the
> common part of the code.
>
> Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>

Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>

>
> ---
> Changes since V2:
>         - Moved the comment from vmx_vmexit_handler to
>           hvm_monitor_debug
>         - Moved the AMD comment up.
> ---
>  xen/arch/x86/hvm/monitor.c    |  5 +++++
>  xen/arch/x86/hvm/svm/svm.c    | 48 
> +++++++++++++++++++++++++++++++++++--------
>  xen/arch/x86/hvm/vmx/vmx.c    |  5 -----
>  xen/include/asm-x86/monitor.h |  4 ++--
>  4 files changed, 47 insertions(+), 15 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
> index 131b852..60cb68d 100644
> --- a/xen/arch/x86/hvm/monitor.c
> +++ b/xen/arch/x86/hvm/monitor.c
> @@ -133,6 +133,11 @@ static inline unsigned long gfn_of_rip(unsigned long rip)
>  int hvm_monitor_debug(unsigned long rip, enum hvm_monitor_debug_type type,
>                        unsigned long trap_type, unsigned long insn_length)
>  {
> +    /*
> +     * rc < 0 error in monitor/vm_event, crash
> +     * !rc    continue normally
> +     * rc > 0 paused waiting for response, work here is done
> +     */
>      struct vcpu *curr = current;
>      struct arch_domain *ad = &curr->domain->arch;
>      vm_event_request_t req = {};
> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> index dcbd550..0d9baf8 100644
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -59,6 +59,7 @@
>  #include <asm/hap.h>
>  #include <asm/apic.h>
>  #include <asm/debugger.h>
> +#include <asm/hvm/monitor.h>
>  #include <asm/xstate.h>
>
>  void svm_asm_do_resume(void);
> @@ -1079,7 +1080,8 @@ static void svm_ctxt_switch_to(struct vcpu *v)
>  static void noreturn svm_do_resume(struct vcpu *v)
>  {
>      struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
> -    bool_t debug_state = v->domain->debugger_attached;
> +    bool debug_state = v->domain->debugger_attached
> +                || v->domain->arch.monitor.software_breakpoint_enabled;
>      bool_t vcpu_guestmode = 0;
>      struct vlapic *vlapic = vcpu_vlapic(v);
>
> @@ -2407,6 +2409,19 @@ static bool svm_get_pending_event(struct vcpu *v, 
> struct x86_event *info)
>      return true;
>  }
>
> +static void svm_propagate_intr(struct vcpu *v, unsigned long insn_len)
> +{
> +    struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
> +    struct x86_event event = {
> +        .vector = vmcb->eventinj.fields.type,
> +        .type = vmcb->eventinj.fields.type,
> +        .error_code = vmcb->exitinfo1,
> +    };
> +
> +    event.insn_len = insn_len;
> +    hvm_inject_event(&event);
> +}
> +
>  static struct hvm_function_table __initdata svm_function_table = {
>      .name                 = "SVM",
>      .cpu_up_prepare       = svm_cpu_up_prepare,
> @@ -2619,14 +2634,31 @@ void svm_vmexit_handler(struct cpu_user_regs *regs)
>          break;
>
>      case VMEXIT_EXCEPTION_BP:
> -        if ( !v->domain->debugger_attached )
> -            goto unexpected_exit_type;
> -        /* AMD Vol2, 15.11: INT3, INTO, BOUND intercepts do not update RIP. 
> */
> -        if ( (inst_len = __get_instruction_length(v, INSTR_INT3)) == 0 )
> +        inst_len = __get_instruction_length(v, INSTR_INT3);
> +
> +        if ( inst_len == 0 )
>              break;
> -        __update_guest_eip(regs, inst_len);
> -        current->arch.gdbsx_vcpu_event = TRAP_int3;
> -        domain_pause_for_debugger();
> +
> +        if ( v->domain->debugger_attached )
> +        {
> +            /* AMD Vol2, 15.11: INT3, INTO, BOUND intercepts do not update 
> RIP. */
> +            __update_guest_eip(regs, inst_len);
> +            current->arch.gdbsx_vcpu_event = TRAP_int3;
> +            domain_pause_for_debugger();
> +        }
> +        else
> +        {
> +           int rc;
> +
> +           rc = hvm_monitor_debug(regs->rip,
> +                                  HVM_MONITOR_SOFTWARE_BREAKPOINT,
> +                                  X86_EVENTTYPE_SW_EXCEPTION,
> +                                  inst_len);
> +           if ( rc < 0 )
> +               goto unexpected_exit_type;
> +           if ( !rc )
> +               svm_propagate_intr(v, inst_len);
> +        }
>          break;
>
>      case VMEXIT_EXCEPTION_NM:
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 3dc6a6d..c89b4b6 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -3709,11 +3709,6 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
>                                         HVM_MONITOR_DEBUG_EXCEPTION,
>                                         trap_type, insn_len);
>
> -                /*
> -                 * rc < 0 error in monitor/vm_event, crash
> -                 * !rc    continue normally
> -                 * rc > 0 paused waiting for response, work here is done
> -                 */
>                  if ( rc < 0 )
>                      goto exit_and_crash;
>                  if ( !rc )
> diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
> index c339324..11a0cae 100644
> --- a/xen/include/asm-x86/monitor.h
> +++ b/xen/include/asm-x86/monitor.h
> @@ -77,13 +77,13 @@ static inline uint32_t 
> arch_monitor_get_capabilities(struct domain *d)
>      if ( !is_hvm_domain(d) )
>          return capabilities;
>
> -    capabilities = (1U << XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST);
> +    capabilities = ((1U << XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST) |
> +                   (1U << XEN_DOMCTL_MONITOR_EVENT_SOFTWARE_BREAKPOINT));
>
>      if( cpu_has_vmx )
>      {
>          capabilities |= (1U << XEN_DOMCTL_MONITOR_EVENT_WRITE_CTRLREG) |
>                         (1U << XEN_DOMCTL_MONITOR_EVENT_MOV_TO_MSR) |
> -                       (1U << XEN_DOMCTL_MONITOR_EVENT_SOFTWARE_BREAKPOINT) |
>                         (1U << XEN_DOMCTL_MONITOR_EVENT_DEBUG_EXCEPTION) |
>                         (1U << XEN_DOMCTL_MONITOR_EVENT_CPUID) |
>                         (1U << XEN_DOMCTL_MONITOR_EVENT_INTERRUPT) |
> --
> 2.7.4

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