linux-kernel - Re: [patch v10 08/10] KVM: x86: process isolation work from VM-entry code path

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Date:   Thu, 3 Feb 2022 19:25:27 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Marcelo Tosatti <mtosatti@...hat.com>
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>
Subject: Re: [patch v10 08/10] KVM: x86: process isolation work from VM-entry
 code path

On Thu, Jan 27, 2022 at 02:30:45PM -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>
> 
> ---
>  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
> @@ -2,8 +2,11 @@
>  
>  #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)
> +static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu,
> +				   unsigned long ti_work,
> +				   unsigned long task_isol_work)
>  {
>  	do {
>  		int ret;
> @@ -25,15 +28,19 @@ static int xfer_to_guest_mode_work(struc
>  		ret = arch_xfer_to_guest_mode_handle_work(vcpu, ti_work);
>  		if (ret)
>  			return ret;
> +		if (task_isol_work)
> +			task_isol_exit_to_user_mode();
>  
>  		ti_work = read_thread_flags();
> -	} while (ti_work & XFER_TO_GUEST_MODE_WORK || need_resched());
> +	} while (ti_work & XFER_TO_GUEST_MODE_WORK || need_resched() ||
> +		 task_isol_work);

There too you should join the XFER_TO_GUEST_MODE_WORK mask.

Thanks.