Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging

small bug fixes

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* tag 'for-upstream' of https://gitlab.com/bonzini/qemu:
  vl: defuse PID file path resolve error
  hw/intc/ioapic: Update KVM routes before redelivering IRQ, on RTE update
  docs/devel: clarify further the semantics of RMW operations
  Fix build without CONFIG_XEN_EMU

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

4 files changed, 21 insertions, 13 deletions

diff --git a/docs/devel/atomics.rst b/docs/devel/atomics.rst
index 633df65a97..81ec26be17 100644
--- a/docs/devel/atomics.rst
+++ b/docs/devel/atomics.rst
@@ -469,13 +469,19 @@ and memory barriers, and the equivalents in QEMU:
   In QEMU, the second kind is named ``atomic_OP_fetch``.
 
 - different atomic read-modify-write operations in Linux imply
-  a different set of memory barriers; in QEMU, all of them enforce
-  sequential consistency.
-
-- in QEMU, ``qatomic_read()`` and ``qatomic_set()`` do not participate in
-  the ordering enforced by read-modify-write operations.
-  This is because QEMU uses the C11 memory model.  The following example
-  is correct in Linux but not in QEMU:
+  a different set of memory barriers. In QEMU, all of them enforce
+  sequential consistency: there is a single order in which the
+  program sees them happen.
+
+- however, according to the C11 memory model that QEMU uses, this order
+  does not propagate to other memory accesses on either side of the
+  read-modify-write operation.  As far as those are concerned, the
+  operation consist of just a load-acquire followed by a store-release.
+  Stores that precede the RMW operation, and loads that follow it, can
+  still be reordered and will happen *in the middle* of the read-modify-write
+  operation!
+
+  Therefore, the following example is correct in Linux but not in QEMU:
 
       +----------------------------------+--------------------------------+
       | Linux (correct)                  | QEMU (incorrect)               |
diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index 6364ecab1b..716ffc8bbb 100644
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -405,6 +405,7 @@ ioapic_mem_write(void *opaque, hwaddr addr, uint64_t val,
                 s->ioredtbl[index] |= ro_bits;
                 s->irq_eoi[index] = 0;
                 ioapic_fix_edge_remote_irr(&s->ioredtbl[index]);
+                ioapic_update_kvm_routes(s);
                 ioapic_service(s);
             }
         }
@@ -417,8 +418,6 @@ ioapic_mem_write(void *opaque, hwaddr addr, uint64_t val,
         ioapic_eoi_broadcast(val);
         break;
     }
-
-    ioapic_update_kvm_routes(s);
 }
 
 static const MemoryRegionOps ioapic_io_ops = {
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 3340f63c37..ea20b23e4c 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2465,10 +2465,11 @@ static void qemu_maybe_daemonize(const char *pid_file)
 
         pid_file_realpath = g_malloc0(PATH_MAX);
         if (!realpath(pid_file, pid_file_realpath)) {
-            error_report("cannot resolve PID file path: %s: %s",
-                         pid_file, strerror(errno));
-            unlink(pid_file);
-            exit(1);
+            if (errno != ENOENT) {
+                warn_report("not removing PID file on exit: cannot resolve PID "
+                            "file path: %s: %s", pid_file, strerror(errno));
+            }
+            return;
         }
 
         qemu_unlink_pidfile_notifier = (struct UnlinkPidfileNotifier) {
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 1aef54f87e..de531842f6 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -4991,6 +4991,7 @@ MemTxAttrs kvm_arch_post_run(CPUState *cpu, struct kvm_run *run)
         kvm_rate_limit_on_bus_lock();
     }
 
+#ifdef CONFIG_XEN_EMU    
     /*
      * If the callback is asserted as a GSI (or PCI INTx) then check if
      * vcpu_info->evtchn_upcall_pending has been cleared, and deassert
@@ -5001,6 +5002,7 @@ MemTxAttrs kvm_arch_post_run(CPUState *cpu, struct kvm_run *run)
     if (x86_cpu->env.xen_callback_asserted) {
         kvm_xen_maybe_deassert_callback(cpu);
     }
+#endif
 
     /* We need to protect the apic state against concurrent accesses from
      * different threads in case the userspace irqchip is used. */