KVM: arm/arm64: Allow setting the timer IRQ numbers from userspace

First we define an ABI using the vcpu devices that lets userspace set
the interrupt numbers for the various timers on both the 32-bit and
64-bit KVM/ARM implementations.

Second, we add the definitions for the groups and attributes introduced
by the above ABI.  (We add the PMU define on the 32-bit side as well for
symmetry and it may get used some day.)

Third, we set up the arch-specific vcpu device operation handlers to
call into the timer code for anything related to the
KVM_ARM_VCPU_TIMER_CTRL group.

Fourth, we implement support for getting and setting the timer interrupt
numbers using the above defined ABI in the arch timer code.

Fifth, we introduce error checking upon enabling the arch timer (which
is called when first running a VCPU) to check that all VCPUs are
configured to use the same PPI for the timer (as mandated by the
architecture) and that the virtual and physical timers are not
configured to use the same IRQ number.

Signed-off-by: Christoffer Dall <cdall@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/virtual/kvm/devices/vcpu.txt b/Documentation/virtual/kvm/devices/vcpu.txt
index d7236a3e01dc..2b5dab16c4f2 100644
--- a/Documentation/virtual/kvm/devices/vcpu.txt
+++ b/Documentation/virtual/kvm/devices/vcpu.txt
@@ -35,3 +35,28 @@ Returns: -ENODEV: PMUv3 not supported or GIC not initialized
 Request the initialization of the PMUv3.  If using the PMUv3 with an in-kernel
 virtual GIC implementation, this must be done after initializing the in-kernel
 irqchip.
+
+
+2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
+Architectures: ARM,ARM64
+
+2.1. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_VTIMER
+2.2. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_PTIMER
+Parameters: in kvm_device_attr.addr the address for the timer interrupt is a
+            pointer to an int
+Returns: -EINVAL: Invalid timer interrupt number
+         -EBUSY:  One or more VCPUs has already run
+
+A value describing the architected timer interrupt number when connected to an
+in-kernel virtual GIC.  These must be a PPI (16 <= intid < 32).  Setting the
+attribute overrides the default values (see below).
+
+KVM_ARM_VCPU_TIMER_IRQ_VTIMER: The EL1 virtual timer intid (default: 27)
+KVM_ARM_VCPU_TIMER_IRQ_PTIMER: The EL1 physical timer intid (default: 30)
+
+Setting the same PPI for different timers will prevent the VCPUs from running.
+Setting the interrupt number on a VCPU configures all VCPUs created at that
+time to use the number provided for a given timer, overwriting any previously
+configured values on other VCPUs.  Userspace should configure the interrupt
+numbers on at least one VCPU after creating all VCPUs and before running any
+VCPUs.