hyperv: fix SynIC SINT assertion failure on guest reset

Resetting a guest that has Hyper-V VMBus support enabled triggers a QEMU
assertion failure:
hw/hyperv/hyperv.c:131: synic_reset: Assertion `QLIST_EMPTY(&synic->sint_routes)' failed.

This happens both on normal guest reboot or when using "system_reset" HMP
command.

The failing assertion was introduced by commit 64ddecc88bcf ("hyperv: SControl is optional to enable SynIc")
to catch dangling SINT routes on SynIC reset.

The root cause of this problem is that the SynIC itself is reset before
devices using SINT routes have chance to clean up these routes.

Since there seems to be no existing mechanism to force reset callbacks (or
methods) to be executed in specific order let's use a similar method that
is already used to reset another interrupt controller (APIC) after devices
have been reset - by invoking the SynIC reset from the machine reset
handler via a new x86_cpu_after_reset() function co-located with
the existing x86_cpu_reset() in target/i386/cpu.c.
Opportunistically move the APIC reset handler there, too.

Fixes: 64ddecc88bcf ("hyperv: SControl is optional to enable SynIc") # exposed the bug
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Message-Id: <cb57cee2e29b20d06f81dce054cbcea8b5d497e8.1664552976.git.maciej.szmigiero@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
index 7fe8cce03e92e83955a4dd5452cac7afbd2b25e4..52f9aa9d8cce733a455f3d5d6a59d5ac680c66ac 100644 (file)
--- a/hw/i386/microvm.c
+++ b/hw/i386/microvm.c
@@ -485,9 +485,7 @@ static void microvm_machine_reset(MachineState *machine)
     CPU_FOREACH(cs) {
         cpu = X86_CPU(cs);
 
-        if (cpu->apic_state) {
-            device_legacy_reset(cpu->apic_state);
-        }
+        x86_cpu_after_reset(cpu);
     }
 }
 

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 566accf7e60a06d25035738b81181f67d24b5ad6..768982ae9a082ca3204c749d3d17d4ec58ea9fbc 100644 (file)
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -92,6 +92,7 @@
 #include "hw/virtio/virtio-mem-pci.h"
 #include "hw/mem/memory-device.h"
 #include "sysemu/replay.h"
+#include "target/i386/cpu.h"
 #include "qapi/qmp/qerror.h"
 #include "e820_memory_layout.h"
 #include "fw_cfg.h"
@@ -1859,9 +1860,7 @@ static void pc_machine_reset(MachineState *machine)
     CPU_FOREACH(cs) {
         cpu = X86_CPU(cs);
 
-        if (cpu->apic_state) {
-            device_legacy_reset(cpu->apic_state);
-        }
+        x86_cpu_after_reset(cpu);
     }
 }
 

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 8a11470507245a17fc9c52edcf6a7a35d60ac6fb..90aec2f462ec1a17f83e459a212ad960814c42cd 100644 (file)
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6035,6 +6035,19 @@ static void x86_cpu_reset(DeviceState *dev)
 #endif
 }
 
+void x86_cpu_after_reset(X86CPU *cpu)
+{
+#ifndef CONFIG_USER_ONLY
+    if (kvm_enabled()) {
+        kvm_arch_after_reset_vcpu(cpu);
+    }
+
+    if (cpu->apic_state) {
+        device_legacy_reset(cpu->apic_state);
+    }
+#endif
+}
+
 static void mce_init(X86CPU *cpu)
 {
     CPUX86State *cenv = &cpu->env;

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 7edf5dfac306b0f98ff725e05dc0c8849e00d0d6..4d21c5759d9d0ea2ba858f8a0bcca4605f739beb 100644 (file)
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -2082,6 +2082,8 @@ typedef struct PropValue {
 } PropValue;
 void x86_cpu_apply_props(X86CPU *cpu, PropValue *props);
 
+void x86_cpu_after_reset(X86CPU *cpu);
+
 uint32_t cpu_x86_virtual_addr_width(CPUX86State *env);
 
 /* cpu.c other functions (cpuid) */

diff --git a/target/i386/kvm/hyperv.c b/target/i386/kvm/hyperv.c
index 9026ef3a81ee7e0ba802c099a9952f04f69c297a..e3ac978648b81cc31fa9f2bd1ba22c3d1ad9a764 100644 (file)
--- a/target/i386/kvm/hyperv.c
+++ b/target/i386/kvm/hyperv.c
@@ -23,6 +23,10 @@ int hyperv_x86_synic_add(X86CPU *cpu)
     return 0;
 }
 
+/*
+ * All devices possibly using SynIC have to be reset before calling this to let
+ * them remove their SINT routes first.
+ */
 void hyperv_x86_synic_reset(X86CPU *cpu)
 {
     hyperv_synic_reset(CPU(cpu));

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index bed6c00f2cb7284b3084191f612be9e34474d659..dac100c67cb9ea9a3f7343e56d4e644d25859522 100644 (file)
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2203,20 +2203,30 @@ void kvm_arch_reset_vcpu(X86CPU *cpu)
         env->mp_state = KVM_MP_STATE_RUNNABLE;
     }
 
+    /* enabled by default */
+    env->poll_control_msr = 1;
+
+    kvm_init_nested_state(env);
+
+    sev_es_set_reset_vector(CPU(cpu));
+}
+
+void kvm_arch_after_reset_vcpu(X86CPU *cpu)
+{
+    CPUX86State *env = &cpu->env;
+    int i;
+
+    /*
+     * Reset SynIC after all other devices have been reset to let them remove
+     * their SINT routes first.
+     */
     if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNIC)) {
-        int i;
         for (i = 0; i < ARRAY_SIZE(env->msr_hv_synic_sint); i++) {
             env->msr_hv_synic_sint[i] = HV_SINT_MASKED;
         }
 
         hyperv_x86_synic_reset(cpu);
     }
-    /* enabled by default */
-    env->poll_control_msr = 1;
-
-    kvm_init_nested_state(env);
-
-    sev_es_set_reset_vector(CPU(cpu));
 }
 
 void kvm_arch_do_init_vcpu(X86CPU *cpu)

diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 2ed586c11b7e74573cf69113d9c14dd1041c0a4b..b7c38ba2c46277b7168bff88d6a6a5e80712de3f 100644 (file)
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -38,6 +38,7 @@ bool kvm_has_adjust_clock_stable(void);
 bool kvm_has_exception_payload(void);
 void kvm_synchronize_all_tsc(void);
 void kvm_arch_reset_vcpu(X86CPU *cs);
+void kvm_arch_after_reset_vcpu(X86CPU *cpu);
 void kvm_arch_do_init_vcpu(X86CPU *cs);
 
 void kvm_put_apicbase(X86CPU *cpu, uint64_t value);