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d="scan'208";a="14533050" Date: Tue, 24 Mar 2020 12:24:44 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: "Tian, Kevin" Message-ID: <20200324112444.GJ24458@Air-de-Roger.citrite.net> References: <20200320190737.42110-1-roger.pau@citrix.com> <20200320190737.42110-4-roger.pau@citrix.com> <20200324095915.GG24458@Air-de-Roger.citrite.net> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: AMSPEX02CAS01.citrite.net (10.69.22.112) To AMSPEX02CL02.citrite.net (10.69.22.126) Subject: Re: [Xen-devel] [PATCH 3/3] x86/nvmx: update exit bitmap on vmexit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: "xen-devel@lists.xenproject.org" , Wei Liu , Jan Beulich , "Nakajima, Jun" , Andrew Cooper Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On Tue, Mar 24, 2020 at 10:16:52AM +0000, Tian, Kevin wrote: > > From: Roger Pau Monné > > Sent: Tuesday, March 24, 2020 5:59 PM > > > > On Tue, Mar 24, 2020 at 06:22:43AM +0000, Tian, Kevin wrote: > > > > From: Roger Pau Monne > > > > Sent: Saturday, March 21, 2020 3:08 AM > > > > > > > > Current code in nvmx_update_apicv set the guest interrupt status field > > > > but doesn't update the exit bitmap, which can cause issues of lost > > > > interrupts on the L1 hypervisor if vmx_intr_assist gets > > > > short-circuited by nvmx_intr_intercept returning true. > > > > > > Above is not accurate. Currently Xen didn't choose to update the EOI > > > exit bitmap every time when there is a change. Instead, it chose to > > > batch the update before resuming to the guest. sort of optimization. > > > So it is not related to whether SVI is changed. We should always do the > > > bitmap update in nvmx_update_apicv, regardless of the setting of > > > Ack-on-exit ... > > > > But if Ack on exit is not set the GUEST_INTR_STATUS won't be changed > > by nvmx_intr_intercept, and hence there's no need to update the EOI > > exit map? > > > > If OTOH the GUEST_INTR_STATUS field is changed by vmx_intr_assist the > > bitmap will already be updated there. > > > > If you agree with my comment in patch 2/3 about setting RVI for > ack-on-exit=0, then EOI bitmap update should be done there too. Yes, I agree, see my reply to your comment. I (again) misremembered the sequence and assumed the switch will happen prior to calling vmx_intr_assist which is not the case. Thanks, Roger.