On Mon, 22 Jul 2013 16:25:35 -0300
Eduardo Habkost <ehabk...@redhat.com> wrote:
> Bug description: QEMU currently gets all bits from GET_SUPPORTED_CPUID
> for CPUID leaf 0xA and passes them directly to the guest. This makes
> the guest ABI depend on host kernel and host CPU capabilities, and
> breaks live migration if we migrate between host with different
> capabilities (e.g. different number of PMU counters).
>
> This patch adds a "pmu-passthrough" property to X86CPU, and set it to
> true only on "-cpu host", or on pc-*-1.5 and older machine-types.
>
> Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
> ---
> include/hw/i386/pc.h | 4 ++++
> target-i386/cpu-qom.h | 7 +++++++
> target-i386/cpu.c | 11 ++++++++++-
> 3 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 7fb97b0..3cea83f 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -235,6 +235,10 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
> .driver = "virtio-net-pci",\
> .property = "any_layout",\
> .value = "off",\
> + },{\
> + .driver = TYPE_X86_CPU,\
> + .property = "pmu-passthrough",\
> + .value = "on",\
> }
>
> #define PC_COMPAT_1_4 \
> diff --git a/target-i386/cpu-qom.h b/target-i386/cpu-qom.h
> index 7e55e5f..b505a45 100644
> --- a/target-i386/cpu-qom.h
> +++ b/target-i386/cpu-qom.h
> @@ -68,6 +68,13 @@ typedef struct X86CPU {
>
> /* Features that were filtered out because of missing host capabilities
> */
> uint32_t filtered_features[FEATURE_WORDS];
> +
> + /* Pass all PMU CPUID bits to the guest directly from
> GET_SUPPORTED_CPUID.
> + * This can't be enabled by default because it breaks live-migration,
> + * as it makes the guest ABI change depending on host CPU/kernel
> + * capabilities.
> + */
> + bool pmu_passthrough;
> } X86CPU;
>
> static inline X86CPU *x86_env_get_cpu(CPUX86State *env)
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 41c81af..e192f63 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -1475,17 +1475,25 @@ static void x86_cpu_get_feature_words(Object *obj,
> Visitor *v, void *opaque,
> error_propagate(errp, err);
> }
>
> +static Property cpu_x86_properties[] = {
> + DEFINE_PROP_BOOL("pmu-passthrough", X86CPU, pmu_passthrough, false),
> + DEFINE_PROP_END_OF_LIST(),
> +};
> +
> static int cpu_x86_find_by_name(X86CPU *cpu, x86_def_t *x86_cpu_def,
> const char *name)
> {
> x86_def_t *def;
> int i;
> + Error *err = NULL;
>
> if (name == NULL) {
> return -1;
> }
> if (kvm_enabled() && strcmp(name, "host") == 0) {
> kvm_cpu_fill_host(x86_cpu_def);
> + object_property_set_bool(OBJECT(cpu), true, "pmu-passthrough", &err);
> + assert_no_error(err);
Could this hunk be implemented using compat props?
That would spare us dealing with it later.
> return 0;
> }
>
> @@ -2017,7 +2025,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
> uint32_t count,
> break;
> case 0xA:
> /* Architectural Performance Monitoring Leaf */
> - if (kvm_enabled()) {
> + if (kvm_enabled() && cpu->pmu_passthrough) {
> KVMState *s = cs->kvm_state;
>
> *eax = kvm_arch_get_supported_cpuid(s, 0xA, count, R_EAX);
> @@ -2516,6 +2524,7 @@ static void x86_cpu_common_class_init(ObjectClass *oc,
> void *data)
> xcc->parent_realize = dc->realize;
> dc->realize = x86_cpu_realizefn;
> dc->bus_type = TYPE_ICC_BUS;
> + dc->props = cpu_x86_properties;
>
> xcc->parent_reset = cc->reset;
> cc->reset = x86_cpu_reset;
