accel: Remove AccelOpsClass::supports_guest_debug

Now accelerators hold the 'guest debug supported' information
in their state, accessible by the common code. No need to call
a per-accelerator handler, simply check for the SSTEP_ENABLE
in AccelGdbConfig::sstep_flags.

Remove all AccelOpsClass::supports_guest_debug implementations,
inline gdb_supports_guest_debug() and remove the now unnecessary
KVMState::have_guest_debug field.

Signed-off-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20260705215729.62196-18-philmd@oss.qualcomm.com>

accel/accel-common.c

@@ -70,6 +70,11 @@ void accel_init_interfaces(AccelClass *ac)
     accel_init_cpu_interfaces(ac);
 }
 
+bool accel_supports_guest_debug(AccelState *accel)
+{
+    return accel->gdbstub.sstep_flags & SSTEP_ENABLE;
+}
+
 void accel_cpu_instance_init(CPUState *cpu)
 {
     if (cpu->cc->accel_cpu && cpu->cc->accel_cpu->cpu_instance_init) {

accel/hvf/hvf-accel-ops.c

@@ -369,7 +369,6 @@ static void hvf_accel_ops_class_init(ObjectClass *oc, const void *data)
     ops->remove_breakpoint = hvf_remove_breakpoint;
     ops->remove_all_breakpoints = hvf_remove_all_breakpoints;
     ops->update_guest_debug = hvf_update_guest_debug;
-    ops->supports_guest_debug = hvf_arch_supports_guest_debug;
 
     ops->get_vcpu_stats = hvf_get_vcpu_stats;
 };

accel/kvm/kvm-accel-ops.c

@@ -105,7 +105,6 @@ static void kvm_accel_ops_class_init(ObjectClass *oc, const void *data)
     ops->synchronize_pre_loadvm = kvm_cpu_synchronize_pre_loadvm;
     ops->handle_interrupt = generic_handle_interrupt;
 
-    ops->supports_guest_debug = kvm_supports_guest_debug;
 #ifdef TARGET_KVM_HAVE_GUEST_DEBUG
     ops->update_guest_debug = kvm_update_guest_debug_ops;
     ops->insert_breakpoint = kvm_insert_breakpoint;

accel/kvm/kvm-all.c

@@ -3036,10 +3036,7 @@ static int kvm_init(AccelState *as, MachineState *ms)
         (kvm_check_extension(s, KVM_CAP_VM_ATTRIBUTES) > 0);
 
 #ifdef TARGET_KVM_HAVE_GUEST_DEBUG
-    s->have_guest_debug =
-        (kvm_check_extension(s, KVM_CAP_SET_GUEST_DEBUG) > 0);
-
-    if (s->have_guest_debug) {
+    if (kvm_check_extension(s, KVM_CAP_SET_GUEST_DEBUG) > 0) {
         as->gdbstub.sstep_flags = SSTEP_ENABLE;
 
         int guest_debug_flags =
@@ -3829,14 +3826,6 @@ int kvm_update_guest_debug(CPUState *cpu, unsigned long reinject_trap)
     return data.err;
 }
 
-bool kvm_supports_guest_debug(void)
-{
-    KVMState *s = KVM_STATE(as);
-
-    /* probed during kvm_init() */
-    return s->have_guest_debug;
-}
-
 int kvm_insert_breakpoint(CPUState *cpu, int type, vaddr addr, vaddr len)
 {
     struct kvm_sw_breakpoint *bp;

accel/kvm/kvm-cpus.h

@@ -16,7 +16,6 @@ void kvm_destroy_vcpu(CPUState *cpu);
 void kvm_cpu_synchronize_post_reset(CPUState *cpu);
 void kvm_cpu_synchronize_post_init(CPUState *cpu);
 void kvm_cpu_synchronize_pre_loadvm(CPUState *cpu);
-bool kvm_supports_guest_debug(void);
 int kvm_insert_breakpoint(CPUState *cpu, int type, vaddr addr, vaddr len);
 int kvm_remove_breakpoint(CPUState *cpu, int type, vaddr addr, vaddr len);
 void kvm_remove_all_breakpoints(CPUState *cpu);

accel/tcg/tcg-accel-ops.c

@@ -109,11 +109,6 @@ void tcg_handle_interrupt(CPUState *cpu, int mask)
     }
 }
 
-static bool tcg_supports_guest_debug(void)
-{
-    return true;
-}
-
 /* Translate GDB watchpoint type to a flags value for cpu_watchpoint_* */
 static inline int xlat_gdb_type(CPUState *cpu, int gdbtype)
 {
@@ -221,7 +216,6 @@ static void tcg_accel_ops_init(AccelClass *ac)
     }
 
     ops->cpu_reset_hold = tcg_cpu_reset_hold;
-    ops->supports_guest_debug = tcg_supports_guest_debug;
     ops->insert_breakpoint = tcg_insert_breakpoint;
     ops->remove_breakpoint = tcg_remove_breakpoint;
     ops->remove_all_breakpoints = tcg_remove_all_breakpoints;

accel/whpx/whpx-accel-ops.c

@@ -82,11 +82,6 @@ static bool whpx_vcpu_thread_is_idle(CPUState *cpu)
     return !whpx_irqchip_in_kernel();
 }
 
-static bool whpx_supports_guest_debug(void)
-{
-    return whpx_arch_supports_guest_debug();
-}
-
 
 static void whpx_accel_ops_class_init(ObjectClass *oc, const void *data)
 {
@@ -96,7 +91,6 @@ static void whpx_accel_ops_class_init(ObjectClass *oc, const void *data)
     ops->kick_vcpu_thread = whpx_kick_vcpu_thread;
     ops->cpu_thread_is_idle = whpx_vcpu_thread_is_idle;
     ops->handle_interrupt = generic_handle_interrupt;
-    ops->supports_guest_debug = whpx_supports_guest_debug;
 
     ops->synchronize_post_reset = whpx_cpu_synchronize_post_reset;
     ops->synchronize_post_init = whpx_cpu_synchronize_post_init;

docs/system/gdb.rst

@@ -54,7 +54,7 @@ While GDB can always fall back to inserting breakpoints into memory
 accelerator. For TCG system emulation we advertise an infinite number
 of hardware assisted breakpoints and watchpoints. For other
 accelerators it will depend on if support has been added (see
-supports_guest_debug and related hooks in AccelOpsClass).
+the AccelGdbConfig structure).
 
 As TCG cannot track all memory accesses in user-mode there is no
 support for watchpoints.

gdbstub/system.c

@@ -331,8 +331,6 @@ static void create_processes(GDBState *s)
     gdb_create_default_process(s);
 }
 
-static bool gdb_supports_guest_debug(void);
-
 bool gdbserver_start(const char *device, Error **errp)
 {
     Chardev *chr = NULL;
@@ -345,7 +343,7 @@ bool gdbserver_start(const char *device, Error **errp)
         return false;
     }
 
-    if (!gdb_supports_guest_debug()) {
+    if (!accel_supports_guest_debug(current_accel())) {
         error_setg(errp, "gdbstub: current accelerator doesn't "
                    "support guest debugging");
         return false;
@@ -624,15 +622,6 @@ int gdb_signal_to_target(int sig)
  * Break/Watch point helpers
  */
 
-static bool gdb_supports_guest_debug(void)
-{
-    const AccelOpsClass *ops = cpus_get_accel();
-    if (ops->supports_guest_debug) {
-        return ops->supports_guest_debug();
-    }
-    return false;
-}
-
 int gdb_breakpoint_insert(CPUState *cs, int type, vaddr addr, vaddr len)
 {
     const AccelOpsClass *ops = cpus_get_accel();

include/accel/accel-cpu-ops.h

@@ -84,7 +84,6 @@ struct AccelOpsClass {
     int64_t (*get_elapsed_ticks)(void);
 
     /* gdbstub hooks */
-    bool (*supports_guest_debug)(void);
     int (*update_guest_debug)(CPUState *cpu);
     int (*insert_breakpoint)(CPUState *cpu, int type, vaddr addr, vaddr len);
     int (*remove_breakpoint)(CPUState *cpu, int type, vaddr addr, vaddr len);

include/qemu/accel.h

@@ -84,4 +84,6 @@ typedef struct AccelGdbConfig {
     bool can_reverse;
 } AccelGdbConfig;
 
+bool accel_supports_guest_debug(AccelState *accel);
+
 #endif /* QEMU_ACCEL_H */

include/system/hvf_int.h

@@ -104,11 +104,6 @@ void hvf_arch_remove_all_hw_breakpoints(void);
  */
 int hvf_update_guest_debug(CPUState *cpu);
 
-/*
- * Return whether the guest supports debugging.
- */
-bool hvf_arch_supports_guest_debug(void);
-
 bool hvf_arch_cpu_realize(CPUState *cpu, Error **errp);
 uint32_t hvf_arch_get_default_ipa_bit_size(void);
 uint32_t hvf_arch_get_max_ipa_bit_size(void);

include/system/kvm_int.h

@@ -118,7 +118,6 @@ struct KVMState
 #endif
     int max_nested_state_len;
     int kvm_shadow_mem;
-    bool have_guest_debug;
     bool kernel_irqchip_allowed;
     bool kernel_irqchip_required;
     OnOffAuto kernel_irqchip_split;

include/system/whpx-all.h

@@ -22,7 +22,4 @@ void whpx_translate_cpu_breakpoints(
 void whpx_arch_destroy_vcpu(CPUState *cpu);
 void whpx_arch_accel_class_init(ObjectClass *oc);
 
-/* called by whpx-accel-ops */
-bool whpx_arch_supports_guest_debug(void);
-
 #endif

target/arm/hvf/hvf.c

@@ -2900,8 +2900,3 @@ void hvf_arch_update_guest_debug(CPUState *cpu)
 
     hvf_arch_set_traps(cpu);
 }
-
-bool hvf_arch_supports_guest_debug(void)
-{
-    return true;
-}

target/arm/whpx/whpx-all.c

@@ -295,11 +295,6 @@ void whpx_translate_cpu_breakpoints(
     /* Breakpoints aren’t supported on this platform */
 }
 
-bool whpx_arch_supports_guest_debug(void) 
-{
-    return false;
-}
-
 void whpx_arch_destroy_vcpu(CPUState *cpu)
 {
     /* currently empty on Arm */

target/i386/hvf/hvf.c

@@ -1066,8 +1066,3 @@ void hvf_arch_remove_all_hw_breakpoints(void)
 void hvf_arch_update_guest_debug(CPUState *cpu)
 {
 }
-
-bool hvf_arch_supports_guest_debug(void)
-{
-    return false;
-}

target/i386/whpx/whpx-all.c

@@ -1853,11 +1853,6 @@ void whpx_apply_breakpoints(
     }
 }
 
-bool whpx_arch_supports_guest_debug(void) 
-{
-    return true;
-}
-
 void whpx_arch_destroy_vcpu(CPUState *cpu)
 {
     X86CPU *x86cpu = X86_CPU(cpu);