Re: [PATCH v3 4/9] irqchip/gic-v2: Parse and export virtual GIC information

Julien Grall
2016-03-14T12:19:19Z

Hi Christoffer,

On 09/03/16 05:14, Christoffer Dall wrote:
> On Tue, Mar 08, 2016 at 11:29:28AM +0000, Julien Grall wrote:
>> For now, the firmware tables are parsed 2 times: once in the GIC
>> drivers, the other timer when initializing the vGIC. It means code
>> duplication and make more tedious to add the support for another
>> firmware table (like ACPI).
>>
>> Introduce a new structure and set of helpers to get/set the virtual GIC
>> information. Also fill up the structure for GICv2.
>>
>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>
>> ---
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Jason Cooper <jason@lakedaemon.net>
>> Cc: Marc Zyngier <marc.zyngier@arm.com>
>>
>> Changes in v2:
>> - Use 0 rather than a negative value to know when the maintenance IRQ
>> is not present.
>> - Use resource for vcpu and vctrl
>> ---
>> drivers/irqchip/irq-gic-common.c | 13 ++++++
>> drivers/irqchip/irq-gic-common.h | 3 ++
>> drivers/irqchip/irq-gic.c | 80 +++++++++++++++++++++++++++++++++-
>> include/linux/irqchip/arm-gic-common.h | 33 ++++++++++++++
>> 4 files changed, 128 insertions(+), 1 deletion(-)
>> create mode 100644 include/linux/irqchip/arm-gic-common.h
>>
>> diff --git a/drivers/irqchip/irq-gic-common.c b/drivers/irqchip/irq-gic-common.c
>> index f174ce0..704caf4 100644
>> --- a/drivers/irqchip/irq-gic-common.c
>> +++ b/drivers/irqchip/irq-gic-common.c
>> @@ -21,6 +21,19 @@
>>
>> #include "irq-gic-common.h"
>>
>> +static const struct gic_kvm_info *gic_kvm_info;
>> +
>> +const struct gic_kvm_info *gic_get_kvm_info(void)
>> +{
>> + return gic_kvm_info;
>> +}
>> +
>> +void gic_set_kvm_info(const struct gic_kvm_info *info)
>> +{
>> + WARN(gic_kvm_info != NULL, "gic_kvm_info already set\n");
>
> why do we WARN here? Wouldn't this be an obvious bug?

Right this is an obvious bug. I will switch to BUG_ON.

>
>> + gic_kvm_info = info;
>> +}
>> +
>> void gic_enable_quirks(u32 iidr, const struct gic_quirk *quirks,
>> void *data)
>> {
>> diff --git a/drivers/irqchip/irq-gic-common.h b/drivers/irqchip/irq-gic-common.h
>> index fff697d..205e5fd 100644
>> --- a/drivers/irqchip/irq-gic-common.h
>> +++ b/drivers/irqchip/irq-gic-common.h
>> @@ -19,6 +19,7 @@
>>
>> #include <linux/of.h>
>> #include <linux/irqdomain.h>
>> +#include <linux/irqchip/arm-gic-common.h>
>>
>> struct gic_quirk {
>> const char *desc;
>> @@ -35,4 +36,6 @@ void gic_cpu_config(void __iomem *base, void (*sync_access)(void));
>> void gic_enable_quirks(u32 iidr, const struct gic_quirk *quirks,
>> void *data);
>>
>> +void gic_set_kvm_info(const struct gic_kvm_info *info);
>> +
>> #endif /* _IRQ_GIC_COMMON_H */
>> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
>> index fbde202..0c58112 100644
>> --- a/drivers/irqchip/irq-gic.c
>> +++ b/drivers/irqchip/irq-gic.c
>> @@ -102,6 +102,8 @@ static struct static_key supports_deactivate = STATIC_KEY_INIT_TRUE;
>>
>> static struct gic_chip_data gic_data[CONFIG_ARM_GIC_MAX_NR] __read_mostly;
>>
>> +static struct gic_kvm_info gic_v2_kvm_info;
>> +
>> #ifdef CONFIG_GIC_NON_BANKED
>> static void __iomem *gic_get_percpu_base(union gic_base *base)
>> {
>> @@ -1189,6 +1191,35 @@ static bool gic_check_eoimode(struct device_node *node, void __iomem **base)
>> return true;
>> }
>>
>> +static void __init gic_of_setup_kvm_info(struct device_node *node)
>> +{
>> + int ret;
>> + struct resource r;
>
> I would prefer two struct resource variables more akin to how the KVM
> code did it already, and then name them something more understandable
> than 'r'.
>
> You could also argue that you can then only populate the gic_v2_kvm_info
> with all coherent info or nothing, instead of filling it out partially
> and then exiting.
>
>> +
>> + gic_v2_kvm_info.type = GIC_V2;
>> +
>> + gic_v2_kvm_info.maint_irq = irq_of_parse_and_map(node, 0);
>> +
>> + ret = of_address_to_resource(node, 2, &r);
>> + if (!ret)
>> + gic_v2_kvm_info.vctrl = r;
>> +
>> + ret = of_address_to_resource(node, 3, &r);
>
> here you're overwriting the error return value if the first call to
> of_address_to_resource failed ?
>
>> + if (!ret) {
>> + if (!PAGE_ALIGNED(r.start))
>> + pr_warn("GICV physical address 0x%llx not page aligned\n",
>> + (unsigned long long)r.start);
>
> how does KVM know that this went bad?
>
>> + else if (!PAGE_ALIGNED(resource_size(&r)))
>> + pr_warn("GICV size 0x%llx not a multiple of page size 0x%lx\n",
>> + (unsigned long long)resource_size(&r),
>> + PAGE_SIZE);
>
> same?
>
>> + else
>> + gic_v2_kvm_info.vcpu = r;
>> + }
>> +
>> + gic_set_kvm_info(&gic_v2_kvm_info);
>
> so here you're setting the kvm info even if one of the calls above
> fails?
>
> I think this function could leverage much more of the existing KVM
> implementation to avoid these kinds of mistakes.

I will rework this function.

>
>> +}
>> +
>> int __init
>> gic_of_init(struct device_node *node, struct device_node *parent)
>> {
>> @@ -1218,8 +1249,10 @@ gic_of_init(struct device_node *node, struct device_node *parent)
>>
>> __gic_init_bases(gic_cnt, -1, dist_base, cpu_base, percpu_offset,
>> &node->fwnode);
>> - if (!gic_cnt)
>> + if (!gic_cnt) {
>> gic_init_physaddr(node);
>> + gic_of_setup_kvm_info(node);
>> + }
>>
>> if (parent) {
>> irq = irq_of_parse_and_map(node, 0);
>> @@ -1248,6 +1281,10 @@ IRQCHIP_DECLARE(pl390, "arm,pl390", gic_of_init);
>> static struct
>> {
>> phys_addr_t cpu_phy_base;
>> + u32 maint_irq;
>> + int maint_irq_mode;
>> + phys_addr_t vctrl_base;
>> + phys_addr_t vcpu_base;
>> } acpi_data __initdata;
>>
>> static int __init
>> @@ -1272,6 +1309,12 @@ gic_acpi_parse_madt_cpu(struct acpi_subtable_header *header,
>> return -EINVAL;
>>
>> acpi_data.cpu_phy_base = gic_cpu_base;
>> + acpi_data.maint_irq = processor->vgic_interrupt;
>> + acpi_data.maint_irq_mode = (processor->flags & ACPI_MADT_VGIC_IRQ_MODE) ?
>> + ACPI_EDGE_SENSITIVE : ACPI_LEVEL_SENSITIVE;
>
> I can only assume that bit 2 set means edge, and the default is leve,
> but I really don't know how ACPI works here.

See Table 5.62 in ACPI 6.0.

>
>> + acpi_data.vctrl_base = processor->gich_base_address;
>> + acpi_data.vcpu_base = processor->gicv_base_address;
>> +
>> cpu_base_assigned = 1;
>> return 0;
>> }
>> @@ -1302,6 +1345,39 @@ static bool __init gic_validate_dist(struct acpi_subtable_header *header,
>>
>> #define ACPI_GICV2_DIST_MEM_SIZE (SZ_4K)
>> #define ACPI_GIC_CPU_IF_MEM_SIZE (SZ_8K)
>> +#define ACPI_GICV2_VCTRL_MEM_SIZE (SZ_4K)
>> +#define ACPI_GICV2_VCPU_MEM_SIZE (SZ_8K)
>> +
>> +static void __init gic_acpi_setup_kvm_info(void)
>> +{
>> + int irq;
>> +
>> + gic_v2_kvm_info.type = GIC_V2;
>> +
>> + irq = acpi_register_gsi(NULL, acpi_data.maint_irq,
>> + acpi_data.maint_irq_mode,
>> + ACPI_ACTIVE_HIGH);
>> + if (irq > 0)
>> + gic_v2_kvm_info.maint_irq = irq;
>> +
>> + if (acpi_data.vctrl_base) {
>> + struct resource *vctrl = &gic_v2_kvm_info.vctrl;
>> +
>> + vctrl->flags = IORESOURCE_MEM;
>> + vctrl->start = acpi_data.vctrl_base;
>> + vctrl->end = vctrl->start + ACPI_GICV2_VCTRL_MEM_SIZE - 1;
>> + }
>> +
>> + if (acpi_data.vcpu_base) {
>> + struct resource *vcpu = &gic_v2_kvm_info.vcpu;
>> +
>> + vcpu->flags = IORESOURCE_MEM;
>> + vcpu->start = acpi_data.vcpu_base;
>> + vcpu->end = vcpu->start + ACPI_GICV2_VCPU_MEM_SIZE - 1;
>> + }
>> +
>> + gic_set_kvm_info(&gic_v2_kvm_info);
>
> again, if something fails above, you're still setting the struct
> pointer.
>
> how will KVM know?

I will rework the function.

>
>> +}
>>
>> static int __init gic_v2_acpi_init(struct acpi_subtable_header *header,
>> const unsigned long end)
>> @@ -1359,6 +1435,8 @@ static int __init gic_v2_acpi_init(struct acpi_subtable_header *header,
>> if (IS_ENABLED(CONFIG_ARM_GIC_V2M))
>> gicv2m_init(NULL, gic_data[0].domain);
>>
>> + gic_acpi_setup_kvm_info();
>> +
>> return 0;
>> }
>> IRQCHIP_ACPI_DECLARE(gic_v2, ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR,
>> diff --git a/include/linux/irqchip/arm-gic-common.h b/include/linux/irqchip/arm-gic-common.h
>> new file mode 100644
>> index 0000000..f7723b9
>> --- /dev/null
>> +++ b/include/linux/irqchip/arm-gic-common.h
>> @@ -0,0 +1,33 @@
>> +/*
>> + * include/linux/irqchip/arm-gic-common.h
>> + *
>> + * Copyright (C) 2016 ARM Limited, All Rights Reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +#ifndef __LINUX_IRQCHIP_ARM_GIC_COMMON_H
>> +#define __LINUX_IRQCHIP_ARM_GIC_COMMON_H
>> +
>> +#include <linux/types.h>
>> +#include <linux/ioport.h>
>> +
>> +enum gic_type {
>> + GIC_V2,
>> +};
>> +
>> +struct gic_kvm_info {
>> + /* GIC type */
>> + enum gic_type type;
>> + /* Physical address & size of virtual cpu interface */
>
> is this a bitwise '&' or did you want to save two ascii characters by
> not writing 'and' ? If the latter, please write 'and'.

I will write 'and'

>
>> + struct resource vcpu;
>> + /* Interrupt number */
>
> if you're going to comment on the fact that this is an interrupt number,
> I would be more interested in knowing if it's a Linux IRQ number or the
> INTID...
>
>> + unsigned int maint_irq;
>> + /* Physical address & size of virtual control interface */
>
> same here

Ditto

>
>> + struct resource vctrl;
>
> I'm actually not convinced the comments on this struct help a lot, but
> ok.

I can rename to "Virtual control interface".

Regards,

--
Julien Grall