ppc/spapr: implement H_SIGNAL_SYS_RESET

The H_SIGNAL_SYS_RESET hcall allows a guest CPU to raise a system reset exception on CPUs within the same guest -- all CPUs, all-but-self, or a specific CPU (including self).

This has not made its way to a PAPR release yet, but we have an hcall number assigned.

H_SIGNAL_SYS_RESET = 0x380

  Syntax:
    hcall(uint64 H_SIGNAL_SYS_RESET, int64 target);

Generate a system reset NMI on the threads indicated by target.

Values for target:
-1 = target all online threads including the caller
-2 = target all online threads except for the caller
All other negative values: reserved
Positive values: The thread to be targeted, obtained from the value of the "ibm,ppc-interrupt-server#s" property of the CPU in the OF device tree.

Semantics:
- Invalid target: return H_Parameter.
- Otherwise: Generate a system reset NMI on target thread(s), return H_Success.

Signed-off-by Nicholas Piggin <[email protected]>

---
Hi,

I have taken into account feedback since last posting, the comments were appreciated.

http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg04881.html

- Improved changelog description.
- Shared code with QEMU NMI injection.
- Move hcall-specific parameter definitions out of header.
- Added an "unofficial" PAPR specification to changelog.

There is interest to improve the community process with PAPR development, but I can't say if/when/how, so this is the best I can do.

* Some additional background information follows *

The Linux powerpc branch has a corresponding change to add this hcall definition:

https://git.kernel.org/cgit/linux/kernel/git/powerpc/linux.git/commit/?h=next&id=53ce299615e587e900548eb6b384c3081b71bbfa

The motivation is to allow a crash or debug event to pull stuck (interrupts disabled) CPUs into the crash/debug handlers. This is in response to a problem encountered in the wild on a customer machine. Linux guest patches to that end were posted for review:

https://lists.ozlabs.org/pipermail/linuxppc-dev/2016-November/150684.html

Additionally, there is ongoing firmware effort to provide a similar service for non-virtualized environments:

https://lists.ozlabs.org/pipermail/skiboot/2016-November/005481.html

Thanks,
Nick

 hw/ppc/spapr.c         |  4 ++--
 hw/ppc/spapr_hcall.c   | 41 +++++++++++++++++++++++++++++++++++++++++
 include/hw/ppc/spapr.h |  5 ++++-
 3 files changed, 47 insertions(+), 3 deletions(-)

hw/ppc/spapr.c +2 -2

index 208ef7b..5d2adf8 100644
@@ -2252,7 +2252,7 @@ static void spapr_machine_finalizefn(Object *obj)
     g_free(spapr->kvm_type);
 }
 
-static void ppc_cpu_do_nmi_on_cpu(CPUState *cs, run_on_cpu_data arg)
+void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg)
 {
     cpu_synchronize_state(cs);
     ppc_cpu_do_system_reset(cs);

@@ -2263,7 +2263,7 @@ static void spapr_nmi(NMIState *n, int cpu_index, Error **errp)
     CPUState *cs;
 
     CPU_FOREACH(cs) {
-        async_run_on_cpu(cs, ppc_cpu_do_nmi_on_cpu, RUN_ON_CPU_NULL);
+        async_run_on_cpu(cs, spapr_do_system_reset_on_cpu, RUN_ON_CPU_NULL);
     }
 }
 

hw/ppc/spapr_hcall.c +41 -0

index 9a9bedf..b61ac9d 100644
@@ -881,6 +881,46 @@ static target_ulong h_set_mode(PowerPCCPU *cpu, sPAPRMachineState *spapr,
     return ret;
 }
 
+#define H_SIGNAL_SYS_RESET_ALL         -1
+#define H_SIGNAL_SYS_RESET_ALLBUTSELF  -2
+
+static target_ulong h_signal_sys_reset(PowerPCCPU *cpu,
+                                       sPAPRMachineState *spapr,
+                                       target_ulong opcode, target_ulong *args)
+{
+    target_long target = args[0];
+    CPUState *cs;
+
+    if (target < 0) {
+        /* Broadcast */
+        if (target < H_SIGNAL_SYS_RESET_ALLBUTSELF) {
+            return H_PARAMETER;
+        }
+
+        CPU_FOREACH(cs) {
+            PowerPCCPU *c = POWERPC_CPU(cs);
+
+            if (target == H_SIGNAL_SYS_RESET_ALLBUTSELF) {
+                if (c == cpu) {
+                    continue;
+                }
+            }
+            run_on_cpu(cs, spapr_do_system_reset_on_cpu, RUN_ON_CPU_NULL);
+        }
+        return H_SUCCESS;
+
+    } else {
+        /* Unicast */
+        CPU_FOREACH(cs) {
+            if (cpu->cpu_dt_id == target) {
+                run_on_cpu(cs, spapr_do_system_reset_on_cpu, RUN_ON_CPU_NULL);
+                return H_SUCCESS;
+            }
+        }
+        return H_PARAMETER;
+    }
+}
+
 typedef struct {
     uint32_t cpu_version;
     Error *err;

@@ -1101,6 +1141,7 @@ static void hypercall_register_types(void)
     /* hcall-splpar */
     spapr_register_hypercall(H_REGISTER_VPA, h_register_vpa);
     spapr_register_hypercall(H_CEDE, h_cede);
+    spapr_register_hypercall(H_SIGNAL_SYS_RESET, h_signal_sys_reset);
 
     /* processor register resource access h-calls */
     spapr_register_hypercall(H_SET_SPRG0, h_set_sprg0);

include/hw/ppc/spapr.h +4 -1

index bd5bcf7..443c425 100644
@@ -347,7 +347,8 @@ struct sPAPRMachineState {
 #define H_XIRR_X                0x2FC
 #define H_RANDOM                0x300
 #define H_SET_MODE              0x31C
-#define MAX_HCALL_OPCODE        H_SET_MODE
+#define H_SIGNAL_SYS_RESET      0x380
+#define MAX_HCALL_OPCODE        H_SIGNAL_SYS_RESET
 
 /* The hcalls above are standardized in PAPR and implemented by pHyp
  * as well.

@@ -662,4 +663,6 @@ int spapr_rng_populate_dt(void *fdt);
 #define SPAPR_LMB_FLAGS_DRC_INVALID 0x00000020
 #define SPAPR_LMB_FLAGS_RESERVED 0x00000080
 
+void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg);
+
 #endif /* HW_SPAPR_H */