linux-kernel - Re: [PATCH 31/35] irqchip/gic-v4.1: Eagerly vmap vPEs

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Date:   Sat, 28 Sep 2019 11:11:42 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Marc Zyngier <maz@...nel.org>, <kvmarm@...ts.cs.columbia.edu>,
        <linux-kernel@...r.kernel.org>
CC:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 31/35] irqchip/gic-v4.1: Eagerly vmap vPEs

On 2019/9/24 2:26, Marc Zyngier wrote:
> Now that we have HW-accelerated SGIs being delivered to VPEs, it
> becomes required to map the VPEs on all ITSs instead of relying
> on the lazy approach that we would use when using the ITS-list
> mechanism.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>   drivers/irqchip/irq-gic-v3-its.c | 39 +++++++++++++++++++++++++-------
>   1 file changed, 31 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 4aae9582182b..a1e8c4c2598a 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -1417,12 +1417,31 @@ static int its_irq_set_irqchip_state(struct irq_data *d,
>   	return 0;
>   }
>   
> +/*
> + * Two favourable cases:
> + *
> + * (a) Either we have a GICv4.1, and all vPEs have to be mapped at all times
> + *     for vSGI delivery
> + *
> + * (b) Or the ITSs do not use a list map, meaning that VMOVP is cheap enough
> + *     and we're better off mapping all VPEs always
> + *
> + * If neither (a) nor (b) is true, then we map VLPIs on demand.
                                                  ^^^^^
vPEs

> + *
> + */
> +static bool gic_requires_eager_mapping(void)
> +{
> +	if (!its_list_map || gic_rdists->has_rvpeid)
> +		return true;
> +
> +	return false;
> +}
> +
>   static void its_map_vm(struct its_node *its, struct its_vm *vm)
>   {
>   	unsigned long flags;
>   
> -	/* Not using the ITS list? Everything is always mapped. */
> -	if (!its_list_map)
> +	if (gic_requires_eager_mapping())
>   		return;
>   
>   	raw_spin_lock_irqsave(&vmovp_lock, flags);
> @@ -1456,7 +1475,7 @@ static void its_unmap_vm(struct its_node *its, struct its_vm *vm)
>   	unsigned long flags;
>   
>   	/* Not using the ITS list? Everything is always mapped. */
> -	if (!its_list_map)
> +	if (gic_requires_eager_mapping())
>   		return;
>   
>   	raw_spin_lock_irqsave(&vmovp_lock, flags);
> @@ -3957,8 +3976,12 @@ static int its_vpe_irq_domain_activate(struct irq_domain *domain,
>   	struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
>   	struct its_node *its;
>   
> -	/* If we use the list map, we issue VMAPP on demand... */
> -	if (its_list_map)
> +	/*
> +	 * If we use the list map, we issue VMAPP on demand... Unless
> +	 * we're on a GICv4.1 and we eagerly map the VPE on all ITSs
> +	 * so that VSGIs can work.
> +	 */
> +	if (!gic_requires_eager_mapping())
>   		return 0;
>   
>   	/* Map the VPE to the first possible CPU */
> @@ -3984,10 +4007,10 @@ static void its_vpe_irq_domain_deactivate(struct irq_domain *domain,
>   	struct its_node *its;
>   
>   	/*
> -	 * If we use the list map, we unmap the VPE once no VLPIs are
> -	 * associated with the VM.
> +	 * If we use the list map on GICv4.0, we unmap the VPE once no
> +	 * VLPIs are associated with the VM.
>   	 */
> -	if (its_list_map)
> +	if (!gic_requires_eager_mapping())
>   		return;
>   
>   	list_for_each_entry(its, &its_nodes, entry) {
> 


Thanks,
zenghui