Re: [RFC PATCH v2 05/19] KVM: arm/arm64: Check that system supports split eoi/deactivate

Marc Zyngier
2017-08-01T11:34:12Z

On 17/07/17 15:27, Christoffer Dall wrote:
> Some systems without proper firmware and/or hardware description data
> don't support the split EOI and deactivate operation.
>
> On such systems, we cannot leave the physical interrupt active after the
> timer handler on the host has run, so we cannot support KVM with an
> in-kernel GIC with the timer changes we about to introduce.
>
> This patch makes sure that trying to initialize the KVM GIC code will
> fail on such systems.
>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <cdall@linaro.org>
> ---
> drivers/irqchip/irq-gic.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> index 090991f..b7e4fed 100644
> --- a/drivers/irqchip/irq-gic.c
> +++ b/drivers/irqchip/irq-gic.c
> @@ -1391,7 +1391,8 @@ int gic_of_init_child(struct device *dev, struct gic_chip_data **gic, int irq)
> return 0;
> }
>
> -static void __init gic_of_setup_kvm_info(struct device_node *node)
> +static void __init gic_of_setup_kvm_info(struct device_node *node,
> + bool supports_deactivate)

Ouch, nasty. This shadows the static key which is also called
supports_deactivate...

> {
> int ret;
> struct resource *vctrl_res = &gic_v2_kvm_info.vctrl;
> @@ -1411,6 +1412,9 @@ static void __init gic_of_setup_kvm_info(struct device_node *node)
> if (ret)
> return;
>
> + if (!supports_deactivate)
> + return;
> +
> gic_set_kvm_info(&gic_v2_kvm_info);

Speaking of which, the static key should already be initialized, so this
could actually read:

if (static_key_true(&supports_deactivate))
gic_set_kvm_info(&gic_v2_kvm_info);

> }
>
> @@ -1419,6 +1423,7 @@ gic_of_init(struct device_node *node, struct device_node *parent)
> {
> struct gic_chip_data *gic;
> int irq, ret;
> + bool has_eoimode;
>
> if (WARN_ON(!node))
> return -ENODEV;
> @@ -1436,7 +1441,8 @@ gic_of_init(struct device_node *node, struct device_node *parent)
> * Disable split EOI/Deactivate if either HYP is not available
> * or the CPU interface is too small.
> */
> - if (gic_cnt == 0 && !gic_check_eoimode(node, &gic->raw_cpu_base))
> + has_eoimode = gic_check_eoimode(node, &gic->raw_cpu_base);
> + if (gic_cnt == 0 && !has_eoimode)
> static_key_slow_dec(&supports_deactivate);
>
> ret = __gic_init_bases(gic, -1, &node->fwnode);
> @@ -1447,7 +1453,7 @@ gic_of_init(struct device_node *node, struct device_node *parent)
>
> if (!gic_cnt) {
> gic_init_physaddr(node);
> - gic_of_setup_kvm_info(node);
> + gic_of_setup_kvm_info(node, has_eoimode);
> }
>
> if (parent) {
>

and we shouldn't need any of this. What do you think?

M.
--
Jazz is not dead. It just smells funny...