RE: [PATCH] x86/hyperv: Properly suspend/resume reenlightenment notifications

[Dexuan Cui]

> From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> Sent: Tuesday, May 12, 2020 9:02 AM
> To: linux-hyperv@xxxxxxxxxxxxxxx
> Cc: Wei Liu <wei.liu@xxxxxxxxxx>; x86@xxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Michael Kelley
> <mikelley@xxxxxxxxxxxxx>; Dexuan Cui <decui@xxxxxxxxxxxxx>; Tianyu Lan
> <Tianyu.Lan@xxxxxxxxxxxxx>
> Subject: [PATCH] x86/hyperv: Properly suspend/resume reenlightenment
> notifications
> 
> Errors during hibernation with reenlightenment notifications enabled were
> reported:
> 
>  [   51.730435] PM: hibernation entry
>  [   51.737435] PM: Syncing filesystems ...
>  ...
>  [   54.102216] Disabling non-boot CPUs ...
>  [   54.106633] smpboot: CPU 1 is now offline
>  [   54.110006] unchecked MSR access error: WRMSR to 0x40000106 (tried
> to
>      write 0x47c72780000100ee) at rIP: 0xffffffff90062f24
>      native_write_msr+0x4/0x20)
>  [   54.110006] Call Trace:
>  [   54.110006]  hv_cpu_die+0xd9/0xf0
>  ...
> 
> Normally, hv_cpu_die() just reassigns reenlightenment notifications to some
> other CPU when the CPU receiving them goes offline. Upon hibernation, there
> is no other CPU which is still online so cpumask_any_but(cpu_online_mask)
> returns >= nr_cpu_ids and using it as hv_vp_index index is incorrect.
> Disable the feature when cpumask_any_but() fails.
> 
> Also, as we now disable reenlightenment notifications upon hibernation we
> need to restore them on resume. Check if hv_reenlightenment_cb was
> previously set and restore from hv_resume().
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---

Looks good to me. Thanks!

Reviewed-by: Dexuan Cui <decui@xxxxxxxxxxxxx>