Re: [PATCH] x86: vdso: fix pvclock races with task migration

From: Radim KrÄmÃÅ
Date: Tue Apr 07 2015 - 08:47:47 EST

2015-04-07 13:11+0200, Paolo Bonzini:
> On 02/04/2015 20:44, Radim KrÄmÃÅ wrote:
> > If we were migrated right after __getcpu, but before reading the
> > migration_count, we wouldn't notice that we read TSC of a different
> > VCPU, nor that KVM's bug made pvti invalid, as only migration_count
> > on source VCPU is increased.
> >
> > Change vdso instead of updating migration_count on destination.
> >
> > Fixes: 0a4e6be9ca17 ("x86: kvm: Revert "remove sched notifier for cross-cpu migrations"")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
> Applying this, but removing the "Fixes" tag because a guest patch cannot
> fix a host patch (it can work around it or complement it).

I think it was correct. Both are guest only, the revert just missed
some races. (0a4e6be9ca17 has misleading commit message ...)
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