[MODERATED] Re: [PATCH v5 19/27] MDSv5 12

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Jan 18, 2019 at 04:50:34PM -0800, speck for Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
> Subject:  mds: Clear CPU on irq poll, unless opted-out
> 
> By default we assume that irq poll handlers running in the irq poll
> softirq might touch user data and we schedule a cpu clear on next
> kernel exit.
> 
> Add interfaces for audited handlers to declare that they are safe.
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Thank you!
> 
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
>  include/linux/irq_poll.h |  2 ++
>  lib/irq_poll.c           | 18 ++++++++++++++++--
>  2 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/irq_poll.h b/include/linux/irq_poll.h
> index 16aaeccb65cb..5f13582f1b8e 100644
> --- a/include/linux/irq_poll.h
> +++ b/include/linux/irq_poll.h
> @@ -15,6 +15,8 @@ struct irq_poll {
>  enum {
>  	IRQ_POLL_F_SCHED	= 0,
>  	IRQ_POLL_F_DISABLE	= 1,
> +
> +	IRQ_POLL_F_NO_USER	= 1<<4,
>  };
>  
>  extern void irq_poll_sched(struct irq_poll *);
> diff --git a/lib/irq_poll.c b/lib/irq_poll.c
> index 86a709954f5a..cb19431f53ec 100644
> --- a/lib/irq_poll.c
> +++ b/lib/irq_poll.c
> @@ -11,6 +11,7 @@
>  #include <linux/cpu.h>
>  #include <linux/irq_poll.h>
>  #include <linux/delay.h>
> +#include <linux/clearcpu.h>
>  
>  static unsigned int irq_poll_budget __read_mostly = 256;
>  
> @@ -111,6 +112,9 @@ static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
>  
>  		budget -= work;
>  
> +		if (!(iop->state & IRQ_POLL_F_NO_USER))
> +			lazy_clear_cpu();
> +
>  		local_irq_disable();
>  
>  		/*
> @@ -168,21 +172,31 @@ void irq_poll_enable(struct irq_poll *iop)
>  EXPORT_SYMBOL(irq_poll_enable);
>  
>  /**
> - * irq_poll_init - Initialize this @iop
> + * irq_poll_init_flags - Initialize this @iop
>   * @iop:      The parent iopoll structure
>   * @weight:   The default weight (or command completion budget)
>   * @poll_fn:  The handler to invoke
> + * @flags:    IRQ_POLL_F_NO_USER if callback does not touch user data.
>   *
>   * Description:
>   *     Initialize and enable this irq_poll structure.
>   **/
> -void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn)
> +void irq_poll_init_flags(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn,
> +			 int flags)
>  {
>  	memset(iop, 0, sizeof(*iop));
>  	INIT_LIST_HEAD(&iop->list);
>  	iop->weight = weight;
>  	iop->poll = poll_fn;
> +	iop->state = flags;
>  }
> +EXPORT_SYMBOL(irq_poll_init_flags);
> +
> +void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn)
> +{
> +	return irq_poll_init_flags(iop, weight, poll_fn, 0);
> +}
> +
>  EXPORT_SYMBOL(irq_poll_init);
>  
>  static int irq_poll_cpu_dead(unsigned int cpu)
> -- 
> 2.17.2