linux-kernel - Re: [patch v11 10/13] KVM: x86: process isolation work from VM-entry code path

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Date:   Thu, 10 Mar 2022 13:35:51 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Nitesh Lal <nilal@...hat.com>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Christoph Lameter <cl@...ux.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alex Belits <abelits@...its.com>, Peter Xu <peterx@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Oscar Shiang <oscar0225@...email.tw>
Subject: Re: [patch v11 10/13] KVM: x86: process isolation work from VM-entry
 code path

On Mon, Feb 07, 2022 at 04:47:07PM +0100, Frederic Weisbecker wrote:
> On Fri, Feb 04, 2022 at 02:35:47PM -0300, Marcelo Tosatti wrote:
> > VM-entry code path is an entry point similar to userspace return
> > when task isolation is concerned.
> > 
> > Call isolation_exit_to_user_mode before VM-enter.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
> > 
> > ---
> > v11
> > - Add TIF_TASK_ISOL bit to thread info flags and use it
> >   to decide whether to perform task isolation work on
> >   return to userspace                                   (Frederic W. Weisbecker)
> > 
> >  include/linux/entry-kvm.h |    4 +++-
> >  kernel/entry/kvm.c        |   18 ++++++++++++++----
> >  2 files changed, 17 insertions(+), 5 deletions(-)
> > 
> > Index: linux-2.6/kernel/entry/kvm.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/entry/kvm.c
> > +++ linux-2.6/kernel/entry/kvm.c
> > @@ -2,6 +2,7 @@
> >  
> >  #include <linux/entry-kvm.h>
> >  #include <linux/kvm_host.h>
> > +#include <linux/task_isolation.h>
> >  
> >  static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
> >  {
> > @@ -22,6 +23,9 @@ static int xfer_to_guest_mode_work(struc
> >  		if (ti_work & _TIF_NOTIFY_RESUME)
> >  			tracehook_notify_resume(NULL);
> >  
> > +		if (ti_work & _TIF_TASK_ISOL)
> > +			task_isol_exit_to_user_mode();
> > +
> >  		ret = arch_xfer_to_guest_mode_handle_work(vcpu, ti_work);
> >  		if (ret)
> >  			return ret;
> > 
> > 
> 
> Do you need this?

Yes, dropped it somehow, thanks.

> 
> diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
> index 07c878d6e323..3588d6071caf 100644
> --- a/include/linux/entry-kvm.h
> +++ b/include/linux/entry-kvm.h
> @@ -18,7 +18,7 @@
>  
>  #define XFER_TO_GUEST_MODE_WORK						\
>  	(_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL |	\
> -	 _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK)
> +	 _TIF_NOTIFY_RESUME | _TIF_TASK_ISOL | ARCH_XFER_TO_GUEST_MODE_WORK)
>  
>  struct kvm_vcpu;
>  
> 
>