On Wed, Aug 29, 2012 at 08:36:30AM -0500, Anthony Liguori wrote: > "Michael S. Tsirkin" <mst@xxxxxxxxxx> writes: > > > In preparation for adding PV EOI support, disable PV EOI by default for > > 1.1 and older machine types, to avoid CPUID changing during migration. > > > > PV EOI can still be enabled/disabled by specifying it explicitly. > > Enable for 1.1 > > -M pc-1.1 -cpu kvm64,+kvm_pv_eoi > > Disable for 1.2 > > -M pc-1.2 -cpu kvm64,-kvm_pv_eoi > > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > As best I can tell, we're papering over an ABI breakage in KVM. > > If an old QEMU attempts to do a live migration on a new kernel, > migrating to an QEMU on a different box with an older kernel, it will > fail because there is state that isn't being migrated. > > This ought to be fixed in the kernel by making these features > whitelisted by userspace. The kernel interfaces are good. They report what's supported and let userspace set the right CPUID bits based on a whitelist. What's broken is the fact that QEMU simply does not have a whitelist for the KVM features, simply blindly enabling everything. I am going to send fixes for that for 1.3. > > Regards, > > Anthony Liguori > > > > --- > > hw/Makefile.objs | 2 +- > > hw/cpu_flags.c | 32 ++++++++++++++++++++++++++++++++ > > hw/cpu_flags.h | 9 +++++++++ > > hw/pc_piix.c | 2 ++ > > target-i386/cpu.c | 8 ++++++++ > > 5 files changed, 52 insertions(+), 1 deletion(-) > > create mode 100644 hw/cpu_flags.c > > create mode 100644 hw/cpu_flags.h > > > > diff --git a/hw/Makefile.objs b/hw/Makefile.objs > > index 850b87b..3f2532a 100644 > > --- a/hw/Makefile.objs > > +++ b/hw/Makefile.objs > > @@ -1,5 +1,5 @@ > > hw-obj-y = usb/ ide/ > > -hw-obj-y += loader.o > > +hw-obj-y += loader.o cpu_flags.o > > hw-obj-$(CONFIG_VIRTIO) += virtio-console.o > > hw-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o > > hw-obj-y += fw_cfg.o > > diff --git a/hw/cpu_flags.c b/hw/cpu_flags.c > > new file mode 100644 > > index 0000000..7a633c0 > > --- /dev/null > > +++ b/hw/cpu_flags.c > > @@ -0,0 +1,32 @@ > > +/* > > + * CPU compatibility flags. > > + * > > + * Copyright (c) 2012 Red Hat Inc. > > + * Author: Michael S. Tsirkin. > > + * > > + * This program is free software; you can redistribute it and/or modify > > + * it under the terms of the GNU General Public License as published by > > + * the Free Software Foundation; either version 2 of the License, or > > + * (at your option) any later version. > > + * > > + * This program is distributed in the hope that it will be useful, > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > + * GNU General Public License for more details. > > + * > > + * You should have received a copy of the GNU General Public License along > > + * with this program; if not, see <http://www.gnu.org/licenses/>. > > + */ > > +#include "hw/cpu_flags.h" > > + > > +static bool kvm_pv_eoi_disabled_state; > > + > > +void disable_kvm_pv_eoi(void) > > +{ > > + kvm_pv_eoi_disabled_state = true; > > +} > > + > > +bool kvm_pv_eoi_disabled(void) > > +{ > > + return kvm_pv_eoi_disabled_state; > > +} > > diff --git a/hw/cpu_flags.h b/hw/cpu_flags.h > > new file mode 100644 > > index 0000000..05777b6 > > --- /dev/null > > +++ b/hw/cpu_flags.h > > @@ -0,0 +1,9 @@ > > +#ifndef HW_CPU_FLAGS_H > > +#define HW_CPU_FLAGS_H > > + > > +#include <stdbool.h> > > + > > +void disable_kvm_pv_eoi(void); > > +bool kvm_pv_eoi_disabled(void); > > + > > +#endif > > diff --git a/hw/pc_piix.c b/hw/pc_piix.c > > index 008d42f..bdbceda 100644 > > --- a/hw/pc_piix.c > > +++ b/hw/pc_piix.c > > @@ -46,6 +46,7 @@ > > #ifdef CONFIG_XEN > > # include <xen/hvm/hvm_info_table.h> > > #endif > > +#include "cpu_flags.h" > > > > #define MAX_IDE_BUS 2 > > > > @@ -371,6 +372,7 @@ static QEMUMachine pc_machine_v1_2 = { > > > > static void pc_machine_v1_1_compat(void) > > { > > + disable_kvm_pv_eoi(); > > } > > > > static void pc_init_pci_v1_1(ram_addr_t ram_size, > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > index 120a2e3..0d02fd1 100644 > > --- a/target-i386/cpu.c > > +++ b/target-i386/cpu.c > > @@ -23,6 +23,7 @@ > > > > #include "cpu.h" > > #include "kvm.h" > > +#include "asm/kvm_para.h" > > > > #include "qemu-option.h" > > #include "qemu-config.h" > > @@ -33,6 +34,7 @@ > > #include "hyperv.h" > > > > #include "hw/hw.h" > > +#include "hw/cpu_flags.h" > > > > /* feature flags taken from "Intel Processor Identification and the CPUID > > * Instruction" and AMD's "CPUID Specification". In cases of disagreement > > @@ -889,6 +891,12 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model) > > > > plus_kvm_features = ~0; /* not supported bits will be filtered out later */ > > > > + /* Disable PV EOI for old machine types. > > + * Feature flags can still override. */ > > + if (kvm_pv_eoi_disabled()) { > > + plus_kvm_features &= ~(0x1 << KVM_FEATURE_PV_EOI); > > + } > > + > > add_flagname_to_bitmaps("hypervisor", &plus_features, > > &plus_ext_features, &plus_ext2_features, &plus_ext3_features, > > &plus_kvm_features, &plus_svm_features); > > -- > > MST > -- Eduardo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
