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

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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>
This commit is contained in:
Paolo Bonzini 2021-03-01 12:14:14 +01:00
parent c6986f16a7
commit 2c933ac6a8
2 changed files with 13 additions and 0 deletions
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7
docs/system/deprecated.rst
View File

@ -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
------------------------------------

6
hw/intc/apic.c
View File

@ -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);