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| author | Marc Zyngier <maz@kernel.org> | 2019-08-18 15:09:47 +0200 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2019-09-09 13:29:09 +0200 |
| commit | 92f35b751c71d14250a401246f2c792e3aa5b386 (patch) | |
| tree | a1a662935b14d6f2922517e1a45a708c182eb6c8 /Documentation | |
| parent | arm64: KVM: Device mappings should be execute-never (diff) | |
| download | linux-92f35b751c71d14250a401246f2c792e3aa5b386.tar.xz linux-92f35b751c71d14250a401246f2c792e3aa5b386.zip | |
KVM: arm/arm64: vgic: Allow more than 256 vcpus for KVM_IRQ_LINE
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.
Whilst we're there, add a clarification about the use of KVM_IRQ_LINE
on arm, which is not completely conditionned by KVM_CAP_IRQCHIP.
Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/virt/kvm/api.txt | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt index 2d067767b617..25931ca1cb38 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 +766,14 @@ 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. + +Note that on arm/arm64, the KVM_CAP_IRQCHIP capability only conditions +injection of interrupts for the in-kernel irqchip. KVM_IRQ_LINE can always +be used for a userspace interrupt controller. + struct kvm_irq_level { union { __u32 irq; /* GSI */ |