From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [PATCH v7 19/19] KVM: ARM64: Add a new kvm ARM PMU device Date: Thu, 17 Dec 2015 09:38:57 +0000 Message-ID: <567282B1.7070105@arm.com> References: <1450169379-12336-1-git-send-email-zhaoshenglong@huawei.com> <1450169379-12336-20-git-send-email-zhaoshenglong@huawei.com> <567032AD.8000206@arm.com> <567036DE.80605@linaro.org> <567038E3.3010102@arm.com> <20151215204739.GK4120@cbox> <56711348.6010406@huawei.com> <56711B99.1000608@huawei.com> <20151216203336.GE24889@cbox> <567262CA.6050905@huawei.com> <20151217083314.2ed36f9f@why.wild-wind.fr.eu.org> <5672753A.8050006@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: Shannon Zhao , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, will.deacon@arm.com, alex.bennee@linaro.org, wei@redhat.com, cov@codeaurora.org, peter.huangpeng@huawei.com, hangaohuai@huawei.com To: Shannon Zhao , Christoffer Dall Return-path: Received: from foss.arm.com ([217.140.101.70]:60174 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751282AbbLQJjC (ORCPT ); Thu, 17 Dec 2015 04:39:02 -0500 In-Reply-To: <5672753A.8050006@huawei.com> Sender: kvm-owner@vger.kernel.org List-ID: On 17/12/15 08:41, Shannon Zhao wrote: > > > On 2015/12/17 16:33, Marc Zyngier wrote: >> On Thu, 17 Dec 2015 15:22:50 +0800 >> Shannon Zhao wrote: >> >>>> >>>> >>>> On 2015/12/17 4:33, Christoffer Dall wrote: >>>>>> On Wed, Dec 16, 2015 at 04:06:49PM +0800, Shannon Zhao wrote: >>>>>>>> Hi, >>>>>>>> >>>>>>>> On 2015/12/16 15:31, Shannon Zhao wrote: >>>>>>>>>>>>>>>>>>>>>> But in this case, you're returning an error if it is *not* initialized. >>>>>>>>>>>>>>>>>>>>>> I understand that in that case you cannot return an interrupt number (-1 >>>>>>>>>>>>>>>>>>>>>> would be weird), but returning -EBUSY feels even more weird. >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>> I'd settle for -ENOXIO, or something similar. Anyone having a better idea? >>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>> ENXIO or ENODEV would be my choice too, and add that to the >>>>>>>>>>>>>> Documentation clearly describing when this error code is used. >>>>>>>>>>>>>> >>>>>>>>>>>>>> By the way, why do you loop over all VCPUS to set the same value when >>>>>>>>>>>>>> you can't do anything per VCPU anyway? It seems to me it's either a >>>>>>>>>>>>>> per-VM property (that you can store on the VM data structure) or it's a >>>>>>>>>>>>>> true per-VCPU property? >>>>>>>>>> This is a per-VCPU property. PMU interrupt could be PPI or SPI. For PPI >>>>>>>>>> the interrupt numbers are same for each vcpu, while for SPI they are >>>>>>>>>> different, so it needs to set them separately. I planned to support both >>>>>>>>>> PPI and SPI. I think I should add support for SPI at this moment and let >>>>>>>>>> users (QEMU) to set these interrupts for each one. >>>>>>>> >>>>>>>> How about below vPMU Documentation? >>>>>>>> >>>>>>>> ARM Virtual Performance Monitor Unit (vPMU) >>>>>>>> =========================================== >>>>>>>> >>>>>>>> Device types supported: >>>>>>>> KVM_DEV_TYPE_ARM_PMU_V3 ARM Performance Monitor Unit v3 >>>>>>>> >>>>>>>> Instantiate one PMU instance for per VCPU through this API. >>>>>>>> >>>>>>>> Groups: >>>>>>>> KVM_DEV_ARM_PMU_GRP_IRQ >>>>>>>> Attributes: >>>>>>>> The attr field of kvm_device_attr encodes two values: >>>>>>>> bits: | 63 .... 32 | 31 .... 0 | >>>>>>>> values: | vcpu_index | irq_num | >>>> BTW, I change this Attribute to below format and pass vcpu_index through >>>> this Attribute while pass irq_num through kvm_device_attr.addr. >>>> Is it fine? >>>> >>>> bits: | 63 .... 32 | 31 .... 0 | >>>> values: | reserved | vcpu_index | >> Using the .addr field for something that is clearly not an address is >> rather odd. Is there any prior usage of that field for something that >> is not an address? > > I see this usage in vgic_attr_regs_access(). But if you prefer previous > one, I'll use that. Ah, you're using the .addr field to point to a userspace value, not to carry the value itself! That'd be fine by me (even if I still prefer the original one), but I'd like others to chime in (I'm quite bad at defining userspace stuff...). Thanks, M. -- Jazz is not dead. It just smells funny...