Re: [Xen-devel] [PATCH 1/5] arm/vtimer: do not let the guest interact with the physical timer

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-06-06 at 12:22 +0100, Stefano Stabellini wrote:
> The guest can read the physical counter but it shouldn't be able to
> cause interrupts of the physical timer to go to the hypervisor.
> Trap physical timer reads/writes in vtimer.c instead.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> ---
>  xen/arch/arm/time.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
> index 1587fa2..d5b71d7 100644
> --- a/xen/arch/arm/time.c
> +++ b/xen/arch/arm/time.c
> @@ -160,8 +160,8 @@ void __cpuinit init_timer_interrupt(void)
>      WRITE_CP64(0, CNTVOFF);     /* No VM-specific offset */
>      WRITE_CP32(0, CNTKCTL);     /* No user-mode access */
>  #if USE_HYP_TIMER
> -    /* Let the VMs read the physical counter and timer so they can tell time 
> */
> -    WRITE_CP32(CNTHCTL_PA|CNTHCTL_TA, CNTHCTL);
> +    /* Do not the VMs program the physical timer, only read the physical 
> counter */

"Do not *let* the VMs..." ?

> +    WRITE_CP32(CNTHCTL_PA, CNTHCTL);
>  #else
>      /* Cannot let VMs access physical counter if we are using it */
>      WRITE_CP32(0, CNTHCTL);



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