Re: [PATCH 0/3] Support userspace irqchip with arch timers

From: Alexander Graf <agraf@suse.de>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/3] Support userspace irqchip with arch timers
Date: Fri, 28 Oct 2016 22:25:50 +0200	[thread overview]
Message-ID: <554F7514-1900-41B4-8DDC-36C00B903164@suse.de> (raw)
In-Reply-To: <56812724-4bac-8265-b6f6-b1ff00308ec0@arm.com>

> Am 28.10.2016 um 17:57 schrieb Marc Zyngier <marc.zyngier@arm.com>:
> 
>> On 28/10/16 16:52, Alexander Graf wrote:
>> 
>> 
>>> Am 28.10.2016 um 16:38 schrieb Marc Zyngier <marc.zyngier@arm.com>:
>>> 
>>> Alex,
>>> 
>>>> On 30/09/16 20:31, Alexander Graf wrote:
>>>> 
>>>> 
>>>>>> On 30.09.16 17:43, Christoffer Dall wrote:
>>>>>> On Fri, Sep 30, 2016 at 05:38:11PM +0200, Alexander Graf wrote:
>>>>>> 
>>>>>> 
>>>>>>> On 30.09.16 16:54, Alexander Graf wrote:
>>>>>>> 
>>>>>>> 
>>>>>>>> On 27.09.16 21:08, Christoffer Dall wrote:
>>>>>>>> Hi Alex,
>>>>>>>> 
>>>>>>>> Marc and I have been looking at this during Linaro connect and have
>>>>>>>> slightly reworked your patch into this small series.
>>>>>>>> 
>>>>>>>> It would be good if you could have a look at it and test it out.
>>>>>>>> 
>>>>>>>> I've tested it with your QEMU, and it works for UP, but secondary CPUs
>>>>>>>> fail to come up, and it looks like the kernel never gets an IPI for
>>>>>>>> those CPUs from userspace.  Any chance you're willing to take a look at
>>>>>>>> that?
>>>>>>> 
>>>>>>> I still need to see whether I can come up with a prettier solution, but
>>>>>>> for now this works:
>>>>>>> 
>>>>>>> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
>>>>>> 
>>>>>> Eh, no, not in i386 code :). But the problem seems to be a missing
>>>>>> mpstate sync.
>>>>>> 
>>>>> Yeah, that looked really dodgy.  Have you tested it? :)
>>>> 
>>>> This time around tested with the correct command line parameters I hope
>>>> :). I'll send a pretty patch later.
>>>> 
>>>> diff --git a/target-arm/kvm.c b/target-arm/kvm.c
>>>> index b4c8fe2..b549f00 100644
>>>> --- a/target-arm/kvm.c
>>>> +++ b/target-arm/kvm.c
>>>> @@ -173,6 +173,12 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>>>>     */
>>>>    kvm_async_interrupts_allowed = true;
>>>> 
>>>> +    /*
>>>> +     * PSCI wakes up secondary cores, so we always need to
>>>> +     * have vCPUs waiting in kernel space
>>>> +     */
>>>> +    kvm_halt_in_kernel_allowed = true;
>>>> +
>>>>    cap_has_mp_state = kvm_check_extension(s, KVM_CAP_MP_STATE);
>>>> 
>>>>    type_register_static(&host_arm_cpu_type_info);
>>> 
>>> What the status of userspace for this thing? Are QEMU patches being
>>> posted and reviewed?
>> 
>> I didn't see a notification that the patches were merged. Are they in
>> Linus' tree yet? Then I can post enablement to qemu-devel.
> 
> I think you got it backward. I have no intention of merging them until I
> see a vague consensus on the userspace API, and a set of patches ready
> to be merged in QEMU.

That's not how kvm apis are made.

Alex