Re: [RFC] Handling CP15 timer without in-kernel irqchip

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On 2 October 2015 at 11:05, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> On 02/10/2015 11:58, Peter Maydell wrote:
>> I definitely dislike the latter -- userspace ends up having to
>> emulate part of the CPU even though that CPU support is really
>> there in hardware. Also it requires us to edit the device tree,
>> which means it won't work at all on boards other than 'virt'
>> where we use the kernel's device tree rather than creating our
>> own. Better for the kernel to forward the timer
>> interrupts back out to userspace's irq controller.
>
> How do boards other than 'virt' work when emulated without KVM?  It must
> be possible to emulate the physical timer in QEMU.

Without KVM is easy -- we emulate the physical timer as just
one of the parts of the emulated CPU. With KVM, we don't emulate
the CPU at all. We don't try to handle a "half TCG half KVM" setup.

thanks
-- PMM
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