Re: [PATCH v3 9/9] kvm/x86: Hyper-V kvm exit

[Andrey Smetanin <asmetanin@virtuozzo.com>]

On 11/03/2015 05:51 PM, Paolo Bonzini wrote:
>
>
> On 03/11/2015 15:36, Andrey Smetanin wrote:
>>>
>>>
>>> if I run a patched QEMU but I *do not* enable the synthetic interrupt
>>> controller.  I can fix it by wrapping the calls to synic_exit with "if
>>> (!host)", but I haven't checked yet the source---so that may not be the
>>> proper fix.  Sorry for not having looked more in detail.
>>>
>> Could you please specify test case(kvm unit tests ?) and kernel/qemu(if
>> it's not standard)?
>
> It happens just by starting QEMU.
>
> Kernel: kvm/queue
> + kvm/irqchip: kvm_arch_irq_routing_update renaming split
> + kvm/x86: split ioapic-handled and EOI exit bitmaps
> + kvm/x86: Hyper-V synthetic interrupt controller
> + kvm/x86: Hyper-V kvm exit
>
> QEMU: 3a958f559ecd
> + standard-headers/x86: add Hyper-V SynIC constants
> + target-i386/kvm: Hyper-V SynIC MSR's support
> + linux-headers/kvm: add Hyper-V SynIC irq routing type and struct
> + kvm: Hyper-V SynIC irq routing support
> + linux-headers/kvm: KVM_EXIT_HYPERV type and struct
> + target-i386/hyperv: Hyper-V SynIC SINT routing and vCPU exit
> + hw/misc: Hyper-V test device 'hyperv-testdev'
>
> Can be reproduced just with
> "../qemu/+build/x86_64-softmmu/qemu-system-x86_64 --enable-kvm -cpu
> kvm64 -display none".
>
Thanks!
We probably found root case -
qemu reads/writes Hyper-V SynIC msrs just by check SynIC MSR's support 
in kernel. So KVM synic exits into userspace(at SynIC MSR's writes), 
while userspace Hyper-V SynIC handler doesn't expect this exit(cpu 
'hv-synic' option is not set), so handler returns -1 and qemu exits.
> Paolo
>