For single stepping (via KVM) of a guest vcpu to work, KVM needs not
only to support the SET_GUEST_DEBUG ioctl but to also recognize the
KVM_GUESTDBG_SINGLESTEP bit in the control field of the
kvm_guest_debug struct.

This patch adds support for querying the single step capability so
that QEMU can decide what to do for the platforms that do not have
such support.

Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
---
 accel/kvm/kvm-all.c  | 7 +++++++
 include/sysemu/kvm.h | 1 +
 2 files changed, 8 insertions(+)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 4e1de942ce..0dc7a32883 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2264,6 +2264,13 @@ bool kvm_arm_supports_user_irq(void)
     return kvm_check_extension(kvm_state, KVM_CAP_ARM_USER_IRQ);
 }
 
+/* Whether the KVM_SET_GUEST_DEBUG ioctl supports single stepping */
+int kvm_has_guestdbg_singlestep(void)
+{
+    /* return kvm_check_extension(kvm_state, KVM_CAP_GUEST_DEBUG_SSTEP); */
+    return 0;
+}
+
 #ifdef KVM_CAP_SET_GUEST_DEBUG
 struct kvm_sw_breakpoint *kvm_find_sw_breakpoint(CPUState *cpu,
                                                  target_ulong pc)
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index a6d1cd190f..ca2bbff053 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -214,6 +214,7 @@ int kvm_has_pit_state2(void);
 int kvm_has_many_ioeventfds(void);
 int kvm_has_gsi_routing(void);
 int kvm_has_intx_set_mask(void);
+int kvm_has_guestdbg_singlestep(void);
 
 int kvm_init_vcpu(CPUState *cpu);
 int kvm_cpu_exec(CPUState *cpu);
-- 
2.17.1

On 19/01/2019 01:07, Fabiano Rosas wrote:
> For single stepping (via KVM) of a guest vcpu to work, KVM needs not
> only to support the SET_GUEST_DEBUG ioctl but to also recognize the
> KVM_GUESTDBG_SINGLESTEP bit in the control field of the
> kvm_guest_debug struct.
> 
> This patch adds support for querying the single step capability so
> that QEMU can decide what to do for the platforms that do not have
> such support.


Belongs to 4/7.


> 
> Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
> ---
>  accel/kvm/kvm-all.c  | 7 +++++++
>  include/sysemu/kvm.h | 1 +
>  2 files changed, 8 insertions(+)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 4e1de942ce..0dc7a32883 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2264,6 +2264,13 @@ bool kvm_arm_supports_user_irq(void)
>      return kvm_check_extension(kvm_state, KVM_CAP_ARM_USER_IRQ);
>  }
>  
> +/* Whether the KVM_SET_GUEST_DEBUG ioctl supports single stepping */
> +int kvm_has_guestdbg_singlestep(void)
> +{
> +    /* return kvm_check_extension(kvm_state, KVM_CAP_GUEST_DEBUG_SSTEP); */
> +    return 0;
> +}
> +
>  #ifdef KVM_CAP_SET_GUEST_DEBUG
>  struct kvm_sw_breakpoint *kvm_find_sw_breakpoint(CPUState *cpu,
>                                                   target_ulong pc)
> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> index a6d1cd190f..ca2bbff053 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -214,6 +214,7 @@ int kvm_has_pit_state2(void);
>  int kvm_has_many_ioeventfds(void);
>  int kvm_has_gsi_routing(void);
>  int kvm_has_intx_set_mask(void);
> +int kvm_has_guestdbg_singlestep(void);
>  
>  int kvm_init_vcpu(CPUState *cpu);
>  int kvm_cpu_exec(CPUState *cpu);
> 

-- 
Alexey