Re: [Qemu-devel] [PATCH] target-i386/machine:fix migrate faile because of Hyper-V HV_X64_MSR_VP_RUNTIME

[Gonglei (Arei)]

> -----Original Message-----
> From: Zhuangyanying
> Sent: Friday, November 04, 2016 4:17 PM
> To: address@hidden; address@hidden; address@hidden
> Cc: address@hidden; Gonglei (Arei); Zhuangyanying
> Subject: [PATCH] target-i386/machine:fix migrate faile because of Hyper-V
> HV_X64_MSR_VP_RUNTIME
> 
> From: ZhuangYanying <address@hidden>
> 
> Hyper-V HV_X64_MSR_VP_RUNTIME was introduced in linux-4.4 + qemu-2.5.
> 
> As long as the KVM module supports, qemu will save / load the
> vmstate_msr_hyperv_runtime register during the migration.
> 
> Regardless of whether the hyperv_runtime configuration of
> x86_cpu_properties is
> enabled.
> 
> The qemu-2.3 does not support this feature, of course, failed to migrate.
> 
> linux-BGSfqC:/home/qemu # ./x86_64-softmmu/qemu-system-x86_64
> --enable-kvm
> -nodefaults -machine pc-i440fx-2.3,accel=kvm,usb=off -smp 4 -m 4096 -drive
> file=/work/suse/sles11sp3.img.bak,format=raw,if=none,id=drive-virtio-disk0,ca
> che=none
> -device
> virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0
> -vnc :99 -device cirrus-vga,id=video0,vgamem_mb=8,bus=pci.0,addr=0x2
> -monitor vc
> 
> save_section_header:se->section_id=3,se->idstr:ram,se->instance_id=0,se->v
> ersion_id=4
> 
> save_section_header:se->section_id=0,se->idstr:timer,se->instance_id=0,se->
> version_id=2
> 
> save_section_header:se->section_id=4,se->idstr:cpu_common,se->instance_id
> =0,se->version_id=1
> 
> save_section_header:se->section_id=5,se->idstr:cpu,se->instance_id=0,se->ve
> rsion_id=12
> 
> vmstate_subsection_save:vmsd->name:cpu/async_pf_msr
> 
> hyperv_runtime_enable_needed:env->msr_hv_runtime=128902811
> 
> vmstate_subsection_save:vmsd->name:cpu/msr_hyperv_runtime
> 
> Since hyperv_runtime is false, vm will not use hv->runtime_offset, then
> vmstate_msr_hyperv_runtime is no need to transfer while migrating.
> 
> Signed-off-by: address@hidden
> ---
> Hi,
> 
> Recently, I tested cross-version migration/rollback between qemu tag v2.3.1
> and
> qemu-master, found that rollback failed.
> 
> linux-rIVrzS:/home/git/qemu # ./x86_64-softmmu/qemu-system-x86_64
> --enable-kvm
> -nodefaults -machine pc-i440fx-2.3,accel=kvm,usb=off -smp 4 -m 4096 -drive
> file=/work/suse/sles11sp3.img.bak,format=raw,if=none,id=drive-virtio-disk0,ca
> che=none
> -device
> virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0
> -vnc :99 -device cirrus-vga,id=video0,vgamem_mb=8,bus=pci.0,addr=0x2
> -monitor vc
> -incoming tcp:0:8888
> 
> qemu-system-x86_64: error while loading state for instance 0x0 of device 'cpu'
> 
> qemu-system-x86_64: load of migration failed: No such file or directory
> 
> Maybe set compat_props on PC_COMPAT_2_5 ? Any better idea?
> ---
>  target-i386/machine.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/target-i386/machine.c b/target-i386/machine.c
> index 48037f1..e984d77 100644
> --- a/target-i386/machine.c
> +++ b/target-i386/machine.c
> @@ -709,6 +709,10 @@ static bool hyperv_runtime_enable_needed(void
> *opaque)
>      X86CPU *cpu = opaque;
>      CPUX86State *env = &cpu->env;
> 
> +    if (!cpu->hyperv_runtime) {
> +        return 0;

'return false' is better. 

Regards,
-Gonglei

> +    }
> +
>      return env->msr_hv_runtime != 0;
>  }
> 
> --
> 1.8.3.1
>