[RFC PATCH 28/33] irqchip/gic-v3-its: Support VPE doorbell invalidation even when !DirectLPI
Shanker Donthineni
shankerd at codeaurora.org
Mon Feb 13 16:44:47 PST 2017
Hi Marc,
On 01/17/2017 04:20 AM, Marc Zyngier wrote:
> When we don't have the DirectLPI feature, we must work around the
> architecture shortcomings to be able to perform the required
> invalidation.
>
> For this, we create a fake device whose sole purpose is to
> provide a way to issue a map/inv/unmap sequence (and the corresponding
> sync operations). That's 6 commands and a full serialization point
> to be able to do this.
>
> You just have hope the hypervisor won't do that too often...
>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
> drivers/irqchip/irq-gic-v3-its.c | 59
> ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 57 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c
> b/drivers/irqchip/irq-gic-v3-its.c
> index 008fb71..3787579 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -133,6 +133,9 @@ struct its_device {
> u32 device_id;
> };
>
> +static struct its_device *vpe_proxy_dev;
> +static DEFINE_RAW_SPINLOCK(vpe_proxy_dev_lock);
> +
> static LIST_HEAD(its_nodes);
> static DEFINE_SPINLOCK(its_lock);
> static struct rdists *gic_rdists;
> @@ -993,8 +996,35 @@ static void lpi_update_config(struct irq_data *d, u8
> clr, u8 set)
> struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
> void __iomem *rdbase;
>
> - rdbase = per_cpu_ptr(gic_rdists->rdist,
> vpe->col_idx)->rd_base;
> - writeq_relaxed(d->hwirq, rdbase + GICR_INVLPIR);
> + if (gic_rdists->has_direct_lpi) {
> + rdbase = per_cpu_ptr(gic_rdists->rdist,
> vpe->col_idx)->rd_base;
> + writeq_relaxed(d->hwirq, rdbase + GICR_INVLPIR);
> + } else {
> + /*
> + * This is insane.
> + *
> + * If a GICv4 doesn't implement Direct LPIs,
> + * the only way to perform an invalidate is to
> + * use a fake device to issue a MAP/INV/UNMAP
> + * sequence. Since each of these commands has
> + * a sync operation, this is really fast. Not.
> + *
> + * We always use event 0, and this serialize
> + * all VPE invalidations in the system.
> + *
> + * Broken by design(tm).
> + */
> + unsigned long flags;
> +
> + raw_spin_lock_irqsave(&vpe_proxy_dev_lock, flags);
> +
> + vpe_proxy_dev->event_map.col_map[0] =
> vpe->col_idx;
> + its_send_mapvi(vpe_proxy_dev, vpe->vpe_db_lpi, 0);
> + its_send_inv(vpe_proxy_dev, 0);
> + its_send_discard(vpe_proxy_dev, 0);
> +
> + raw_spin_unlock_irqrestore(&vpe_proxy_dev_lock,
> flags);
> + }
> }
> }
>
> @@ -2481,6 +2511,31 @@ static struct irq_domain *its_init_vpe_domain(void)
> struct fwnode_handle *handle;
> struct irq_domain *domain;
>
> + if (gic_rdists->has_direct_lpi) {
> + pr_info("ITS: Using DirectLPI for VPE invalidation\n");
> + } else {
> + struct its_node *its;
> +
> + list_for_each_entry(its, &its_nodes, entry) {
> + u32 devid;
> +
> + if (!its->is_v4)
> + continue;
> +
> + /* Use the last possible DevID */
> + devid = GENMASK(its->device_ids - 1, 0);
How do we know this 'devid' is not being used by real hardware devices?
I think we need some kind check in its_msi_prepare() to skip this device
or WARN.
Unfortunately Qualcomm doesn't support Direct LPI feature.
--
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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