From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [RFC PATCH v2 13/22] xen/arm: its: Add virtual ITS command support Date: Tue, 5 May 2015 13:03:00 +0100 Message-ID: <5548B174.7020002@citrix.com> References: <1426775889-29442-1-git-send-email-vijay.kilari@gmail.com> <553FB23F.7090200@citrix.com> <5540C6D5.9020400@citrix.com> <5540DE16.4090900@citrix.com> <55411D1F.4090308@citrix.com> <5541FF51.6060907@citrix.com> <55423C44.6070702@citrix.com> <5548A525.5070608@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini , Julien Grall Cc: Ian Campbell , Vijay Kilari , Prasun Kapoor , Vijaya Kumar K , Julien Grall , Tim Deegan , "xen-devel@lists.xen.org" , Stefano Stabellini , manish.jaggi@caviumnetworks.com List-Id: xen-devel@lists.xenproject.org On 05/05/15 12:57, Stefano Stabellini wrote: > On Tue, 5 May 2015, Julien Grall wrote: >>> I think we should pause the guest vcpu until we receive >>> the interrupt. >>> You can do that by calling vcpu_block. >> >> Blocking the vcpu is not the right thing to do. The processing of the >> ITS command queue is asynchronous and the guest may decide to execute >> other task while waiting. > > Sure, but the hypervisor might have other things to do and other vcpus > to schedule as well. It is a matter of priorities and scheduling the > most appropriate workload. Keep in mind that vcpu_block doesn't > completely pause the guest, it just only blocks the vcpu until the next > guest event occurs. I don't think it will help to get the guest booting faster. Linux is trying to read CREADR (The completion register) every millisecond. I suspect we will receive an IRQ faster than that. Regards, -- Julien Grall