Re: [PATCH v4 6/9] irqchip/gic-v3: Parse and export virtual GIC information

Marc Zyngier
2016-04-01T10:25:18Z

On 01/04/16 11:13, Christoffer Dall wrote:
> On Thu, Mar 24, 2016 at 05:53:40PM +0000, Julien Grall wrote:
>> Fill up the recently introduced gic_kvm_info with the hardware
>> information used for virtualization.
>>
>> 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 v4:
>> - Change the flow to call gic_kvm_set_info only when all the
>> mandatory information are valid.
>> - Remove unecessary code in ACPI parsing (the virtual control
>> interface doesn't exist for GICv3).
>> - Rework commit message
>> - Rework the ACPI support as it didn't collect hardware info for
>> virtualization when there is more than 1 redistributor region
>>
>> Changes in v3:
>> - Add ACPI support
>>
>> 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-v3.c | 123 ++++++++++++++++++++++++++++++++-
>> include/linux/irqchip/arm-gic-common.h | 1 +
>> 2 files changed, 123 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
>> index 50e87e6..b5ed8be 100644
>> --- a/drivers/irqchip/irq-gic-v3.c
>> +++ b/drivers/irqchip/irq-gic-v3.c
>> @@ -28,6 +28,7 @@
>> #include <linux/slab.h>
>>
>> #include <linux/irqchip.h>
>> +#include <linux/irqchip/arm-gic-common.h>
>> #include <linux/irqchip/arm-gic-v3.h>
>>
>> #include <asm/cputype.h>
>> @@ -56,6 +57,8 @@ struct gic_chip_data {
>> static struct gic_chip_data gic_data __read_mostly;
>> static struct static_key supports_deactivate = STATIC_KEY_INIT_TRUE;
>>
>> +static struct gic_kvm_info gic_v3_kvm_info;
>> +
>> #define gic_data_rdist() (this_cpu_ptr(gic_data.rdists.rdist))
>> #define gic_data_rdist_rd_base() (gic_data_rdist()->rd_base)
>> #define gic_data_rdist_sgi_base() (gic_data_rdist_rd_base() + SZ_64K)
>> @@ -901,6 +904,39 @@ static int __init gic_validate_dist_version(void __iomem *dist_base)
>> return 0;
>> }
>>
>> +static void __init gic_of_setup_kvm_info(struct device_node *node)
>> +{
>> + int ret;
>> + struct resource r;
>> + u32 gicv_idx;
>> +
>> + gic_v3_kvm_info.type = GIC_V3;
>> +
>> + gic_v3_kvm_info.maint_irq = irq_of_parse_and_map(node, 0);
>> + if (!gic_v3_kvm_info.maint_irq)
>> + return;
>> +
>> + if (of_property_read_u32(node, "#redistributor-regions",
>> + &gicv_idx))
>> + gicv_idx = 1;
>> +
>> + gicv_idx += 3; /* Also skip GICD, GICC, GICH */
>> + ret = of_address_to_resource(node, gicv_idx, &r);
>> + if (!ret) {
>> + if (!PAGE_ALIGNED(r.start))
>> + pr_warn("GICV physical address 0x%llx not page aligned\n",
>> + (unsigned long long)r.start);
>> + 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);
>> + else
>
> it seems like you're also checking the above items in the KVM code
> itself, so I still don't understand why we have to do this twice.
>
> My feeling here is that you want to just lookup if you have the proper
> resources to fill in the struct in the GIC driver, and fill in the
> struct with data if the firmware gave you something.
>
> It's then up to KVM to deal with its constraints, such as the resources
> being page-aligned etc. But I suppose you could also argue that the GIC
> code knows how this hardware resource can or cannot be used and
> therefore should check it.

That's definitely a KVM limitation more than anything else. I had
patches to deal with that, and could revive them... So the check should
IMO only occur at the KVM level, not in the GIC driver.

Thanks,

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