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Re: [Qemu-devel] [PATCH v2] ppc: spapr-rtas - implement os-term rtas cal


From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH v2] ppc: spapr-rtas - implement os-term rtas call
Date: Tue, 17 Jun 2014 12:02:08 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.6.0


On 17.06.14 11:59, Nikunj A Dadhania wrote:
Alexander Graf <address@hidden> writes:

On 17.06.14 11:30, Nikunj A Dadhania wrote:
Alexander Graf <address@hidden> writes:

On 12.06.14 14:09, Nikunj A Dadhania wrote:
PAPR compliant guest calls this in absence of kdump. After
receiving this call qemu could trigger a guest dump. This guest dump
can be used to analyse using crash tool.

Signed-off-by: Nikunj A Dadhania <address@hidden>
---

v2: indentation fixes

    hw/ppc/spapr_rtas.c | 32 ++++++++++++++++++++++++++++++++
    1 file changed, 32 insertions(+)

diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index ea4a2b2..f030e73 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -29,6 +29,8 @@
    #include "sysemu/char.h"
    #include "hw/qdev.h"
    #include "sysemu/device_tree.h"
+#include "qapi/qmp/qjson.h"
+#include "monitor/monitor.h"
#include "hw/ppc/spapr.h"
    #include "hw/ppc/spapr_vio.h"
@@ -267,6 +269,34 @@ static void rtas_ibm_set_system_parameter(PowerPCCPU *cpu,
        rtas_st(rets, 0, ret);
    }
+static void rtas_ibm_os_term(PowerPCCPU *cpu,
+                             sPAPREnvironment *spapr,
+                             uint32_t token, uint32_t nargs,
+                             target_ulong args,
+                             uint32_t nret, target_ulong rets)
+{
+    target_ulong ret = 0;
+    QObject *data;
+
+    data = qobject_from_jsonf("{ 'action': %s }", "pause");
+    monitor_protocol_event(QEVENT_GUEST_PANICKED, data);
+    qobject_decref(data);
+    vm_stop(RUN_STATE_GUEST_PANICKED);
+
+    rtas_st(rets, 0, ret);
+}
+
+static void rtas_ibm_ext_os_term(PowerPCCPU *cpu,
+                                 sPAPREnvironment *spapr,
+                                 uint32_t token, uint32_t nargs,
+                                 target_ulong args,
+                                 uint32_t nret, target_ulong rets)
+{
+    target_ulong ret = 0;
+
+    rtas_st(rets, 0, ret);
+}
+
    static struct rtas_call {
        const char *name;
        spapr_rtas_fn fn;
@@ -392,6 +422,8 @@ static void core_rtas_register_types(void)
                            rtas_ibm_get_system_parameter);
        spapr_rtas_register("ibm,set-system-parameter",
                            rtas_ibm_set_system_parameter);
+    spapr_rtas_register("ibm,os-term", rtas_ibm_os_term);
+    spapr_rtas_register("ibm,extended-os-term", rtas_ibm_ext_os_term);
Why do we need the extended-os-term if we don't do anything with it?
Linux kernel checks for both of them because of legacy:

arch/powerpc/kernel/rtas.c:

void rtas_os_term(char *str)
{
[...]
          /*
           * Firmware with the ibm,extended-os-term property is guaranteed
           * to always return from an ibm,os-term call. Earlier versions without
           * this property may terminate the partition which we want to avoid
           * since it interferes with panic_timeout.
But we do not return from the RTAS call, so we don't adhere to the
extended semantics?
But you would return without calling os-term call if
ibm,extended-os-term isnt registered. For that reason I h       ave defined a
stub.

I appreciate the hacker mentality, but Linux explicitly checks on ibm,extended-os-term to ensure that the hypervisor does not stop the VM when it calls ibm,os-term. However, the implementation above does stop the VM when the guest calls ibm,os-term.

Why was that check put into place?


Alex




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