[Qemu-devel] [PATCH] Migration compatibility for serial

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Older QEMUs dont understand the new (sub)sections that
may be generated in the serial device.   Limit their generation
to newer machine types.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 hw/char/serial.c         | 19 +++++++++++++------
 hw/i386/pc_piix.c        |  2 ++
 hw/i386/pc_q35.c         |  2 ++
 hw/ppc/spapr.c           |  2 ++
 include/hw/char/serial.h |  3 +++
 5 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/hw/char/serial.c b/hw/char/serial.c
index 513d73c..ef31df3 100644
--- a/hw/char/serial.c
+++ b/hw/char/serial.c
@@ -103,6 +103,9 @@ do { fprintf(stderr, "serial: " fmt , ## __VA_ARGS__); } while (0)
 do {} while (0)
 #endif
 
+/* Force migration compatibility of pre-2.2 machine types */
+bool serial_migrate_pre_2_2;
+
 static void serial_receive1(void *opaque, const uint8_t *buf, int size);
 
 static inline void recv_fifo_put(SerialState *s, uint8_t chr)
@@ -646,6 +649,10 @@ static bool serial_thr_ipending_needed(void *opaque)
 {
     SerialState *s = opaque;
 
+    if (serial_migrate_pre_2_2) {
+        return false;
+    }
+
     if (s->ier & UART_IER_THRI) {
         bool expected_value = ((s->iir & UART_IIR_ID) == UART_IIR_THRI);
         return s->thr_ipending != expected_value;
@@ -672,7 +679,7 @@ static const VMStateDescription vmstate_serial_thr_ipending = {
 static bool serial_tsr_needed(void *opaque)
 {
     SerialState *s = (SerialState *)opaque;
-    return s->tsr_retry != 0;
+    return !serial_migrate_pre_2_2 && s->tsr_retry != 0;
 }
 
 static const VMStateDescription vmstate_serial_tsr = {
@@ -691,7 +698,7 @@ static const VMStateDescription vmstate_serial_tsr = {
 static bool serial_recv_fifo_needed(void *opaque)
 {
     SerialState *s = (SerialState *)opaque;
-    return !fifo8_is_empty(&s->recv_fifo);
+    return !serial_migrate_pre_2_2 && !fifo8_is_empty(&s->recv_fifo);
 
 }
 
@@ -709,7 +716,7 @@ static const VMStateDescription vmstate_serial_recv_fifo = {
 static bool serial_xmit_fifo_needed(void *opaque)
 {
     SerialState *s = (SerialState *)opaque;
-    return !fifo8_is_empty(&s->xmit_fifo);
+    return !serial_migrate_pre_2_2 && !fifo8_is_empty(&s->xmit_fifo);
 }
 
 static const VMStateDescription vmstate_serial_xmit_fifo = {
@@ -726,7 +733,7 @@ static const VMStateDescription vmstate_serial_xmit_fifo = {
 static bool serial_fifo_timeout_timer_needed(void *opaque)
 {
     SerialState *s = (SerialState *)opaque;
-    return timer_pending(s->fifo_timeout_timer);
+    return !serial_migrate_pre_2_2 && timer_pending(s->fifo_timeout_timer);
 }
 
 static const VMStateDescription vmstate_serial_fifo_timeout_timer = {
@@ -743,7 +750,7 @@ static const VMStateDescription vmstate_serial_fifo_timeout_timer = {
 static bool serial_timeout_ipending_needed(void *opaque)
 {
     SerialState *s = (SerialState *)opaque;
-    return s->timeout_ipending != 0;
+    return !serial_migrate_pre_2_2 && s->timeout_ipending != 0;
 }
 
 static const VMStateDescription vmstate_serial_timeout_ipending = {
@@ -760,7 +767,7 @@ static const VMStateDescription vmstate_serial_timeout_ipending = {
 static bool serial_poll_needed(void *opaque)
 {
     SerialState *s = (SerialState *)opaque;
-    return s->poll_msl >= 0;
+    return !serial_migrate_pre_2_2 && s->poll_msl >= 0;
 }
 
 static const VMStateDescription vmstate_serial_poll = {
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index e142f75..d6d596c 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -39,6 +39,7 @@
 #include "hw/kvm/clock.h"
 #include "sysemu/sysemu.h"
 #include "hw/sysbus.h"
+#include "hw/char/serial.h"
 #include "hw/cpu/icc_bus.h"
 #include "sysemu/arch_init.h"
 #include "sysemu/block-backend.h"
@@ -344,6 +345,7 @@ static void pc_compat_2_1(MachineState *machine)
     x86_cpu_compat_set_features("core2duo", FEAT_1_ECX, CPUID_EXT_VMX, 0);
     x86_cpu_compat_kvm_no_autodisable(FEAT_8000_0001_ECX, CPUID_EXT3_SVM);
     pcms->enforce_aligned_dimm = false;
+    serial_migrate_pre_2_2 = true;
 }
 
 static void pc_compat_2_0(MachineState *machine)
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index b68263d..a211f21 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -32,6 +32,7 @@
 #include "sysemu/arch_init.h"
 #include "hw/i2c/smbus.h"
 #include "hw/boards.h"
+#include "hw/char/serial.h"
 #include "hw/timer/mc146818rtc.h"
 #include "hw/xen/xen.h"
 #include "sysemu/kvm.h"
@@ -328,6 +329,7 @@ static void pc_compat_2_1(MachineState *machine)
     x86_cpu_compat_set_features("coreduo", FEAT_1_ECX, CPUID_EXT_VMX, 0);
     x86_cpu_compat_set_features("core2duo", FEAT_1_ECX, CPUID_EXT_VMX, 0);
     x86_cpu_compat_kvm_no_autodisable(FEAT_8000_0001_ECX, CPUID_EXT3_SVM);
+    serial_migrate_pre_2_2 = true;
 }
 
 static void pc_compat_2_0(MachineState *machine)
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 01f8da8..f2673da 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -39,6 +39,7 @@
 #include "qom/cpu.h"
 
 #include "hw/boards.h"
+#include "hw/char/serial.h"
 #include "hw/ppc/ppc.h"
 #include "hw/loader.h"
 
@@ -1863,6 +1864,7 @@ static void spapr_compat_2_2(Object *obj)
 static void spapr_compat_2_1(Object *obj)
 {
     spapr_compat_2_2(obj);
+    serial_migrate_pre_2_2 = true;
 }
 
 static void spapr_machine_2_3_instance_init(Object *obj)
diff --git a/include/hw/char/serial.h b/include/hw/char/serial.h
index 15beb6b..527d728 100644
--- a/include/hw/char/serial.h
+++ b/include/hw/char/serial.h
@@ -94,4 +94,7 @@ SerialState *serial_mm_init(MemoryRegion *address_space,
 #define TYPE_ISA_SERIAL "isa-serial"
 void serial_hds_isa_init(ISABus *bus, int n);
 
+/* Force migration compatibility of pre-2.2 machine types */
+extern bool serial_migrate_pre_2_2;
+
 #endif
-- 
2.4.3