KVM: x86: deprecate -M kernel-irqchip=off except for -M isapc

The userspace local APIC is basically untested and does not support many
features such as TSC deadline timer, x2APIC or PV spinlocks.  On the
other hand, the PIT and IOAPIC are okay as they are not tied to
the processor and are tested with -M kernel-irqchip=split.

Therefore, deprecate the local APIC and, with it, limit
-M kernel-irqchip=off to the ISA PC machine type, which does not
have a local APIC at all.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index 561c916da2103b2a74b7f509cbde09efed4b2bee..fcf0ca40680ee45914b5e9767f296004ba1adf62 100644 (file)
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -153,6 +153,13 @@ The ``-writeconfig`` option is not able to serialize the entire contents
 of the QEMU command line.  It is thus considered a failed experiment
 and deprecated, with no current replacement.
 
+Userspace local APIC with KVM (x86, since 6.0)
+''''''''''''''''''''''''''''''''''''''''''''''
+
+Using ``-M kernel-irqchip=off`` with x86 machine types that include a local
+APIC is deprecated.  The ``split`` setting is supported, as is using
+``-M kernel-irqchip=off`` with the ISA PC machine type.
+
 QEMU Machine Protocol (QMP) commands
 ------------------------------------
 

diff --git a/hw/intc/apic.c b/hw/intc/apic.c
index 3ada22f427054b88bf97bc7ca1c1929ee93256c2..f4f50f974e6cacb450b30f936fd35ae8c6493392 100644 (file)
--- a/hw/intc/apic.c
+++ b/hw/intc/apic.c
@@ -25,6 +25,7 @@
 #include "hw/intc/i8259.h"
 #include "hw/pci/msi.h"
 #include "qemu/host-utils.h"
+#include "sysemu/kvm.h"
 #include "trace.h"
 #include "hw/i386/apic-msidef.h"
 #include "qapi/error.h"
@@ -875,6 +876,11 @@ static void apic_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    if (kvm_enabled()) {
+        warn_report("Userspace local APIC is deprecated for KVM.");
+        warn_report("Do not use kernel-irqchip except for the -M isapc machine type.");
+    }
+
     memory_region_init_io(&s->io_memory, OBJECT(s), &apic_io_ops, s, "apic-msi",
                           APIC_SPACE_SIZE);