[Qemu-devel] [RFC PATCH v3 3/7] kvm: support checking for single step capability

[Fabiano Rosas <farosas@linux.ibm.com>]

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