Sebastien Boeuf 0d0d19e223 vmm: Enable TSC_DEADLINE_TIMER allows for PIT emulation removal ...

As mentioned in the KVM documentation, TSC_DEADLINE_TIMER feature
needs some special checks to validate that it is supported as the
cpuid will always report it as disabled.

We need to use the KVM_CHECK_EXTENSION ioctl to request the value
of KVM_CAP_TSC_DEADLINE_TIMER. In case it is supported through
the local APIC emulation provided by the CREATE_IRQCHIP in KVM,
we have to set manually this feature by patching the cpuid.

Here quoted from the KVM documentation:
```
The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always
returned as false, since the feature depends on KVM_CREATE_IRQCHIP
for local APIC support. Instead it is reported via

  ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER)

if that returns true and you use KVM_CREATE_IRQCHIP, or if you
emulate the feature in userspace, then you can enable the feature
for KVM_SET_CPUID2.
```
This patch implements the behavior described above, and this allows
the VMM to remove the emulated Programmable Interval Timer (PIT) when
the TSC_DEADLINE_TIMER feature can be enabled.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

2019-06-10 09:11:47 -07:00

..

src

vmm: Enable TSC_DEADLINE_TIMER allows for PIT emulation removal

2019-06-10 09:11:47 -07:00

Cargo.toml

dep: Rely on latest kvm-ioctls crate

2019-06-06 15:27:35 +01:00