[Qemu-devel] [PATCH 1/1] kvm: log available guest crash parameters

[Denis V. Lunev]

From: Anton Nefedov <address@hidden>

Windows reports BSOD parameters through Hyper-V crash MSRs. This
information is very useful for initial crash analysis and thus
it would be nice to see it in the QEMU log file. There is suitable
log mask for the purpose.

Linux guest does not provide this information, but still it would
be nice to log that we have crashed.

Signed-off-by: Anton Nefedov <address@hidden>
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Paolo Bonzini <address@hidden>
CC: Marcelo Tosatti <address@hidden>
CC: Richard Henderson <address@hidden>
CC: Eduardo Habkost <address@hidden>
---
 hw/misc/pvpanic.c    |  1 +
 include/sysemu/kvm.h |  2 ++
 kvm-all.c            |  1 +
 stubs/Makefile.objs  |  1 +
 stubs/kvm-crash.c    |  8 ++++++++
 target/i386/kvm.c    | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 64 insertions(+)
 create mode 100644 stubs/kvm-crash.c

diff --git a/hw/misc/pvpanic.c b/hw/misc/pvpanic.c
index 0ac1e6a..221aa4e 100644
--- a/hw/misc/pvpanic.c
+++ b/hw/misc/pvpanic.c
@@ -42,6 +42,7 @@ static void handle_event(int event)
     }
 
     if (event & PVPANIC_PANICKED) {
+        qemu_log_mask(LOG_GUEST_ERROR, "Guest panicked\n");
         qemu_system_guest_panicked();
         return;
     }
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 3045ee7..70cab9d 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -527,4 +527,6 @@ int kvm_set_one_reg(CPUState *cs, uint64_t id, void 
*source);
  */
 int kvm_get_one_reg(CPUState *cs, uint64_t id, void *target);
 int kvm_get_max_memslots(void);
+
+void kvm_arch_log_crash(CPUState *cpu);
 #endif
diff --git a/kvm-all.c b/kvm-all.c
index 330219e..5f83389 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -2000,6 +2000,7 @@ int kvm_cpu_exec(CPUState *cpu)
                 ret = EXCP_INTERRUPT;
                 break;
             case KVM_SYSTEM_EVENT_CRASH:
+                kvm_arch_log_crash(cpu);
                 qemu_mutex_lock_iothread();
                 qemu_system_guest_panicked();
                 qemu_mutex_unlock_iothread();
diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index a187295..3b1632a 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -35,3 +35,4 @@ stub-obj-y += qmp_pc_dimm_device_list.o
 stub-obj-y += target-monitor-defs.o
 stub-obj-y += target-get-monitor-def.o
 stub-obj-y += pc_madt_cpu_entry.o
+stub-obj-y += kvm-crash.o
diff --git a/stubs/kvm-crash.c b/stubs/kvm-crash.c
new file mode 100644
index 0000000..36ab7f0
--- /dev/null
+++ b/stubs/kvm-crash.c
@@ -0,0 +1,8 @@
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "sysemu/kvm.h"
+
+void kvm_arch_log_crash(CPUState *cs)
+{
+    return;
+}
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 3b52821..899a83c 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -2020,6 +2020,36 @@ static int kvm_get_sregs(X86CPU *cpu)
     return 0;
 }
 
+static int kvm_read_msr_hv_crash(X86CPU *cpu, uint64_t *buf)
+{
+    int i, ret;
+    struct {
+        struct kvm_msrs info;
+        struct kvm_msr_entry entries[HV_X64_MSR_CRASH_PARAMS];
+    } msr_data;
+
+    if (!has_msr_hv_crash) {
+        return -ENOSYS;
+    }
+
+    for (i = 0; i < HV_X64_MSR_CRASH_PARAMS; i++) {
+        msr_data.entries[i].index = HV_X64_MSR_CRASH_P0 + i;
+    }
+    msr_data.info.nmsrs = HV_X64_MSR_CRASH_PARAMS;
+
+    ret = kvm_vcpu_ioctl(CPU(cpu), KVM_GET_MSRS, &msr_data);
+    if (ret < 0) {
+        return ret;
+    }
+
+    for (i = 0; i < ret; i++) {
+        const struct kvm_msr_entry *msr = msr_data.entries + i;
+        buf[msr->index - HV_X64_MSR_CRASH_P0] = msr->data;
+    }
+
+    return 0;
+}
+
 static int kvm_get_msrs(X86CPU *cpu)
 {
     CPUX86State *env = &cpu->env;
@@ -2767,6 +2797,27 @@ int kvm_arch_get_registers(CPUState *cs)
     return ret;
 }
 
+void kvm_arch_log_crash(CPUState *cs)
+{
+    uint64_t msrs[HV_X64_MSR_CRASH_PARAMS];
+    int ret;
+    X86CPU *cpu = X86_CPU(cs);
+
+    qemu_log_mask(LOG_GUEST_ERROR, "Guest crashed\n");
+    if (!has_msr_hv_crash) {
+        return;
+    }
+
+    ret = kvm_read_msr_hv_crash(cpu, msrs);
+    if (ret < 0) {
+        qemu_log_mask(LOG_GUEST_ERROR, "Failed to get HV crash parameters\n");
+        return;
+    }
+    qemu_log_mask(LOG_GUEST_ERROR, "HV crash parameters: (%#"PRIx64
+                  " %#"PRIx64" %#"PRIx64" %#"PRIx64" %#"PRIx64")\n",
+                  msrs[0], msrs[1], msrs[2], msrs[3], msrs[4]);
+}
+
 void kvm_arch_pre_run(CPUState *cpu, struct kvm_run *run)
 {
     X86CPU *x86_cpu = X86_CPU(cpu);
-- 
2.7.4