[PATCH v4 01/40] KVM: arm/arm64: Avoid vcpu_load for other vcpu ioctls than KVM_RUN

[Marc Zyngier]

On Thu, 15 Feb 2018 21:02:53 +0000,
Christoffer Dall wrote:
> 
> Calling vcpu_load() registers preempt notifiers for this vcpu and calls
> kvm_arch_vcpu_load().  The latter will soon be doing a lot of heavy
> lifting on arm/arm64 and will try to do things such as enabling the
> virtual timer and setting us up to handle interrupts from the timer
> hardware.
> 
> Loading state onto hardware registers and enabling hardware to signal
> interrupts can be problematic when we're not actually about to run the
> VCPU, because it makes it difficult to establish the right context when
> handling interrupts from the timer, and it makes the register access
> code difficult to reason about.
> 
> Luckily, now when we call vcpu_load in each ioctl implementation, we can
> simply remove the call from the non-KVM_RUN vcpu ioctls, and our
> kvm_arch_vcpu_load() is only used for loading vcpu content to the
> physical CPU when we're actually going to run the vcpu.
> 
> Reviewed-by: Julien Grall <julien.grall at arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>

Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>

	M.

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