From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH 3/7] vhost_vdpa: implement IRQ offloading functions in vhost_vdpa Date: Wed, 15 Jul 2020 17:42:33 +0800 Message-ID: References: <1594565366-3195-1-git-send-email-lingshan.zhu@intel.com> <1594565366-3195-3-git-send-email-lingshan.zhu@intel.com> <3fb9ecfc-a325-69b5-f5b7-476a5683a324@redhat.com> <8f52ee3a-7a08-db14-9194-8085432481a4@intel.com> <2bd946e3-1524-efa5-df2b-3f6da66d2069@redhat.com> <61c1753a-43dc-e448-6ece-13a19058e621@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <61c1753a-43dc-e448-6ece-13a19058e621@intel.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org To: "Zhu, Lingshan" , mst@redhat.com, alex.williamson@redhat.com, pbonzini@redhat.com, sean.j.christopherson@intel.com, wanpengli@tencent.com Cc: virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, netdev@vger.kernel.org, dan.daly@intel.com List-Id: virtualization@lists.linuxfoundation.org On 2020/7/15 下午5:20, Zhu, Lingshan wrote: >>>> >>>> I meant something like: >>>> >>>> unregister(); >>>> vq->call_ctx.producer.token = ctx; >>>> register(); >>> This is what we are doing now, or I must missed somethig: >>> if (ctx && ctx != token) { >>>     irq_bypass_unregister_producer(&vq->call_ctx.producer); >>>     vq->call_ctx.producer.token = ctx; >>>     irq_bypass_register_producer(&vq->call_ctx.producer); >>> >>> } >>> >>> It just unregister and register. >> >> >> I meant there's probably no need for the check and another check and >> unregister before. The whole function is as simple as I suggested above. >> >> Thanks > IMHO we still need the checks, this function handles three cases: > (1)if the ctx == token, we do nothing. For this unregister and register can work, but waste of time. But we have a more simple code and we don't care about the performance here since the operations is rare. > (2)if token exists but ctx is NULL, this means user space issued an unbind, so we need to only unregister the producer. Note that the register/unregister have a graceful check of whether or not there's a token. > (3)if ctx exists and ctx!=token, this means there is a new ctx, we need to update producer by unregister and register. > > I think we can not simply handle all these cases by "unregister and register". So it looks to me the functions are equivalent. Thanks > > Thanks, > BR > Zhu Lingshan