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Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older c
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types |
Date: |
Wed, 29 Aug 2012 11:03:18 -0300 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Wed, Aug 29, 2012 at 08:36:30AM -0500, Anthony Liguori wrote:
> "Michael S. Tsirkin" <address@hidden> 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 <address@hidden>
>
> 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
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, (continued)
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Anthony Liguori, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Gleb Natapov, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Anthony Liguori, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types, Eduardo Habkost, 2012/08/29
- [Qemu-devel] [QEMU 1.2 PATCH] i386: kvm: have a predefined set of default KVM feature bits, Eduardo Habkost, 2012/08/29
- Re: [Qemu-devel] [QEMU 1.2 PATCH] i386: kvm: have a predefined set of default KVM feature bits, Michael S. Tsirkin, 2012/08/29
- Re: [Qemu-devel] [QEMU 1.2 PATCH] i386: kvm: have a predefined set of default KVM feature bits, Marcelo Tosatti, 2012/08/29
- Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types,
Eduardo Habkost <=
[Qemu-devel] [PATCHv4 2/4] pc: refactor compat code, Michael S. Tsirkin, 2012/08/28
[Qemu-devel] [PATCHv4 4/4] kvm: get/set PV EOI MSR, Michael S. Tsirkin, 2012/08/28