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hw/intc/arm_gic_kvm: Don't assume kernel can provide a GICv2 

In our KVM GICv2 realize function, we try to cope with old kernels
that don't provide the device control API (KVM_CAP_DEVICE_CTRL): we
try to use the device control, and if that fails we fall back to
assuming that the kernel has the old style KVM_CREATE_IRQCHIP and
that it will provide a GICv2.

This doesn't cater for the possibility of a kernel and hardware which
only provide a GICv3, which is very common now.  On that setup we
will abort() later on in kvm_arm_pmu_set_irq() when we try to wire up
an interrupt to the GIC we failed to create:

qemu-system-aarch64: PMU: KVM_SET_DEVICE_ATTR: Invalid argument
qemu-system-aarch64: failed to set irq for PMU
Aborted

If the kernel advertises KVM_CAP_DEVICE_CTRL we should trust it if it
says it can't create a GICv2, rather than assuming it has one.  We
can then produce a more helpful error message including a hint about
the most probable reason for the failure.

If the kernel doesn't advertise KVM_CAP_DEVICE_CTRL then it is truly
ancient by this point but we might as well still fall back to a
KVM_CREATE_IRQCHIP GICv2.

With this patch then the user misconfiguration which previously
caused an abort now prints:
qemu-system-aarch64: Initialization of device kvm-arm-gic failed: error creating in-kernel VGIC: No such device
Perhaps the host CPU does not support GICv2?

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Tested-by: Andrew Jones <drjones@redhat.com>
Message-id: 20200225182435.1131-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2020-02-25 18:24:35 +00:00
parent 957e615503
commit 1904f9b5f1
1 changed files with 9 additions and 0 deletions
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9
hw/intc/arm_gic_kvm.c
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@ -551,7 +551,16 @@ static void kvm_arm_gic_realize(DeviceState *dev, Error **errp)
KVM_DEV_ARM_VGIC_CTRL_INIT, NULL, true,
&error_abort);
}
} else if (kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
error_setg_errno(errp, -ret, "error creating in-kernel VGIC");
error_append_hint(errp,
"Perhaps the host CPU does not support GICv2?\n");
} else if (ret != -ENODEV && ret != -ENOTSUP) {
/*
* Very ancient kernel without KVM_CAP_DEVICE_CTRL: assume that
* ENODEV or ENOTSUP mean "can't create GICv2 with KVM_CREATE_DEVICE",
* and that we will get a GICv2 via KVM_CREATE_IRQCHIP.
*/
error_setg_errno(errp, -ret, "error creating in-kernel VGIC");
return;
}