On 23/02/2017 14:34, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> Migration from a 2.3.0 qemu results in a reboot on the receiving QEMU
> due to a disagreement about SM (System management) interrupts.
>
> 2.3.0 didn't have much SMI support, but it did set CPU_INTERRUPT_SMI
> and this gets into the migration stream, but on 2.3.0 it
> never got delivered.
>
> ~2.4.0 SMI interrupt support was added but was broken - so
> that when a 2.3.0 stream was received it cleared the CPU_INTERRUPT_SMI
> but never actually caused an interrupt.
>
> The SMI delivery was recently fixed by 68c6efe07a, but the
> effect now is that an incoming 2.3.0 stream takes the interrupt it
> had flagged but it's bios can't actually handle it(I think
> partly due to the original interrupt not being taken during boot?).
> The consequence is a triple(?) fault and a reboot.
>
> Tested from:
> 2.3.1 -M 2.3.0
> 2.7.0 -M 2.3.0
> 2.8.0 -M 2.3.0
> 2.8.0 -M 2.8.0
>
> This corresponds to RH bugzilla entry 1420679.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> include/hw/i386/pc.h | 4 ++++
> target/i386/cpu.c | 2 ++
> target/i386/cpu.h | 3 +++
> target/i386/kvm.c | 7 ++++++-
> 4 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 079e8d9..cb49826 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -624,6 +624,10 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t
> *);
> .driver = "Broadwell-noTSX" "-" TYPE_X86_CPU,\
> .property = "xlevel",\
> .value = stringify(0x8000000a),\
> + },{\
> + .driver = TYPE_X86_CPU,\
> + .property = "kvm-no-smi-migration",\
> + .value = "on",\
> },
>
> #define PC_COMPAT_2_2 \
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index fd7add2..b2058cd 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -3708,6 +3708,8 @@ static Property x86_cpu_properties[] = {
> DEFINE_PROP_BOOL("cpuid-0xb", X86CPU, enable_cpuid_0xb, true),
> DEFINE_PROP_BOOL("lmce", X86CPU, enable_lmce, false),
> DEFINE_PROP_BOOL("l3-cache", X86CPU, enable_l3_cache, true),
> + DEFINE_PROP_BOOL("kvm-no-smi-migration", X86CPU, kvm_no_smi_migration,
> + false),
> DEFINE_PROP_BOOL("vmware-cpuid-freq", X86CPU, vmware_cpuid_freq, true),
> DEFINE_PROP_END_OF_LIST()
> };
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 8df124f..c5dfef8 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -1255,6 +1255,9 @@ struct X86CPU {
> /* if true override the phys_bits value with a value read from the host
> */
> bool host_phys_bits;
>
> + /* Stop SMI delivery for migration compatibility with old machines */
> + bool kvm_no_smi_migration;
> +
> /* Number of physical address bits supported */
> uint32_t phys_bits;
>
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 27fd050..5bfe633 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -2531,7 +2531,12 @@ static int kvm_put_vcpu_events(X86CPU *cpu, int level)
> events.smi.pending = 0;
> events.smi.latched_init = 0;
> }
> - events.flags |= KVM_VCPUEVENT_VALID_SMM;
> + /* Stop SMI delivery on old machine types to avoid a reboot
> + * on an inward migration of an old VM.
> + */
> + if (!cpu->kvm_no_smi_migration) {
> + events.flags |= KVM_VCPUEVENT_VALID_SMM;
> + }
> }
>
> if (level >= KVM_PUT_RESET_STATE) {
>
Queued, thanks.
Paolo
