Hi Marc,
On 8/18/19 4:07 PM, Marc Zyngier wrote:
> While parts of the VGIC support a large number of vcpus (we
> bravely allow up to 512), other parts are more limited.
>
> One of these limits is visible in the KVM_IRQ_LINE ioctl, which
> only allows 256 vcpus to be signalled when using the CPU or PPI
> types. Unfortunately, we've cornered ourselves badly by allocating
> all the bits in the irq field.
>
> Since the irq_type subfield (8 bit wide) is currently only taking
> the values 0, 1 and 2 (and we have been careful not to allow anything
> else), let's reduce this field to only 4 bits, and allocate the
> remaining 4 bits to a vcpu2_index, which acts as a multiplier:
>
> vcpu_id = 256 * vcpu2_index + vcpu_index
>
> With that, and a new capability (KVM_CAP_ARM_IRQ_LINE_LAYOUT_2)
> allowing this to be discovered, it becomes possible to inject
> PPIs to up to 4096 vcpus. But please just don't.
>
> Reported-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> Documentation/virt/kvm/api.txt | 8 ++++++--
> arch/arm/include/uapi/asm/kvm.h | 4 +++-
> arch/arm64/include/uapi/asm/kvm.h | 4 +++-
> include/uapi/linux/kvm.h | 1 +
> virt/kvm/arm/arm.c | 2 ++
> 5 files changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
> index 2d067767b617..85518bfb2a99 100644
> --- a/Documentation/virt/kvm/api.txt
> +++ b/Documentation/virt/kvm/api.txt
> @@ -753,8 +753,8 @@ in-kernel irqchip (GIC), and for in-kernel irqchip can tell the GIC to
> use PPIs designated for specific cpus. The irq field is interpreted
> like this:
>
> - bits: | 31 ... 24 | 23 ... 16 | 15 ... 0 |
> - field: | irq_type | vcpu_index | irq_id |
> + bits: | 31 ... 28 | 27 ... 24 | 23 ... 16 | 15 ... 0 |
> + field: | vcpu2_index | irq_type | vcpu_index | irq_id |
>
> The irq_type field has the following values:
> - irq_type[0]: out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ
> @@ -766,6 +766,10 @@ The irq_type field has the following values:
>
> In both cases, level is used to assert/deassert the line.
>
> +When KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 is supported, the target vcpu is
> +identified as (256 * vcpu2_index + vcpu_index). Otherwise, vcpu2_index
> +must be zero.
> +
> struct kvm_irq_level {
> union {
> __u32 irq; /* GSI */
> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
> index a4217c1a5d01..2769360f195c 100644
> --- a/arch/arm/include/uapi/asm/kvm.h
> +++ b/arch/arm/include/uapi/asm/kvm.h
> @@ -266,8 +266,10 @@ struct kvm_vcpu_events {
> #define KVM_DEV_ARM_ITS_CTRL_RESET 4
>
> /* KVM_IRQ_LINE irq field index values */
> +#define KVM_ARM_IRQ_VCPU2_SHIFT 28
> +#define KVM_ARM_IRQ_VCPU2_MASK 0xf
> #define KVM_ARM_IRQ_TYPE_SHIFT 24
> -#define KVM_ARM_IRQ_TYPE_MASK 0xff
> +#define KVM_ARM_IRQ_TYPE_MASK 0xf
> #define KVM_ARM_IRQ_VCPU_SHIFT 16
> #define KVM_ARM_IRQ_VCPU_MASK 0xff
> #define KVM_ARM_IRQ_NUM_SHIFT 0
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 9a507716ae2f..67c21f9bdbad 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -325,8 +325,10 @@ struct kvm_vcpu_events {
> #define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1
>
> /* KVM_IRQ_LINE irq field index values */
> +#define KVM_ARM_IRQ_VCPU2_SHIFT 28
> +#define KVM_ARM_IRQ_VCPU2_MASK 0xf
> #define KVM_ARM_IRQ_TYPE_SHIFT 24
> -#define KVM_ARM_IRQ_TYPE_MASK 0xff
> +#define KVM_ARM_IRQ_TYPE_MASK 0xf
> #define KVM_ARM_IRQ_VCPU_SHIFT 16
> #define KVM_ARM_IRQ_VCPU_MASK 0xff
> #define KVM_ARM_IRQ_NUM_SHIFT 0
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 5e3f12d5359e..5414b6588fbb 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -996,6 +996,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_ARM_PTRAUTH_ADDRESS 171
> #define KVM_CAP_ARM_PTRAUTH_GENERIC 172
> #define KVM_CAP_PMU_EVENT_FILTER 173
> +#define KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 174
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 35a069815baf..c1385911de69 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -182,6 +182,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> int r;
> switch (ext) {
> case KVM_CAP_IRQCHIP:
> + case KVM_CAP_ARM_IRQ_LINE_LAYOUT_2:
> r = vgic_present;
> break;
> case KVM_CAP_IOEVENTFD:
> @@ -888,6 +889,7 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
>
> irq_type = (irq >> KVM_ARM_IRQ_TYPE_SHIFT) & KVM_ARM_IRQ_TYPE_MASK;
> vcpu_idx = (irq >> KVM_ARM_IRQ_VCPU_SHIFT) & KVM_ARM_IRQ_VCPU_MASK;
> + vcpu_idx += ((irq >> KVM_ARM_IRQ_VCPU2_SHIFT) & KVM_ARM_IRQ_VCPU2_MASK) * (KVM_ARM_IRQ_VCPU_MASK + 1);
> irq_num = (irq >> KVM_ARM_IRQ_NUM_SHIFT) & KVM_ARM_IRQ_NUM_MASK;
>
> trace_kvm_irq_line(irq_type, vcpu_idx, irq_num, irq_level->level);
>
Thank you for the patch!
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
Eric
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