On Tue, Apr 14, 2015 at 07:37:44AM +0000, Wu, Feng wrote: > > > > -----Original Message----- > > From: Marcelo Tosatti [mailto:mtosatti@xxxxxxxxxx] > > Sent: Tuesday, March 31, 2015 7:56 AM > > To: Wu, Feng > > Cc: hpa@xxxxxxxxx; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; x86@xxxxxxxxxx; > > gleb@xxxxxxxxxx; pbonzini@xxxxxxxxxx; dwmw2@xxxxxxxxxxxxx; > > joro@xxxxxxxxxx; alex.williamson@xxxxxxxxxx; jiang.liu@xxxxxxxxxxxxxxx; > > eric.auger@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx > > Subject: Re: [v3 24/26] KVM: Update Posted-Interrupts Descriptor when vCPU > > is blocked > > > > On Mon, Mar 30, 2015 at 04:46:55AM +0000, Wu, Feng wrote: > > > > > > > > > > -----Original Message----- > > > > From: Marcelo Tosatti [mailto:mtosatti@xxxxxxxxxx] > > > > Sent: Saturday, March 28, 2015 3:30 AM > > > > To: Wu, Feng > > > > Cc: hpa@xxxxxxxxx; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; > > x86@xxxxxxxxxx; > > > > gleb@xxxxxxxxxx; pbonzini@xxxxxxxxxx; dwmw2@xxxxxxxxxxxxx; > > > > joro@xxxxxxxxxx; alex.williamson@xxxxxxxxxx; jiang.liu@xxxxxxxxxxxxxxx; > > > > eric.auger@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > > iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx > > > > Subject: Re: [v3 24/26] KVM: Update Posted-Interrupts Descriptor when > > vCPU > > > > is blocked > > > > > > > > On Fri, Mar 27, 2015 at 06:34:14AM +0000, Wu, Feng wrote: > > > > > > > Currently, the following code is executed before local_irq_disable() is > > > > called, > > > > > > > so do you mean 1)moving local_irq_disable() to the place before it. 2) > > after > > > > > > interrupt > > > > > > > is disabled, set KVM_REQ_EVENT in case the ON bit is set? > > > > > > > > > > > > 2) after interrupt is disabled, set KVM_REQ_EVENT in case the ON bit > > > > > > is set. > > > > > > > > > > Here is my understanding about your comments here: > > > > > - Disable interrupts > > > > > - Check 'ON' > > > > > - Set KVM_REQ_EVENT if 'ON' is set > > > > > > > > > > Then we can put the above code inside " if > > > > (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) " > > > > > just like it used to be. However, I still have some questions about this > > > > comment: > > > > > > > > > > 1. Where should I set KVM_REQ_EVENT? In function vcpu_enter_guest(), > > or > > > > other places? > > > > > > > > See below: > > > > > > > > > If in vcpu_enter_guest(), since currently local_irq_disable() is called after > > > > 'KVM_REQ_EVENT' > > > > > is checked, is it helpful to set KVM_REQ_EVENT after local_irq_disable() is > > > > called? > > > > > > > > local_irq_disable(); > > > > > > > > *** add code here *** > > > > > > So we need add code like the following here, right? > > > > > > if ('ON' is set) > > > kvm_make_request(KVM_REQ_EVENT, vcpu); > > > > Hi Marcelo, > > I changed the code as above, then I found that the ping latency was extremely big, (70ms - 400ms). > I digged into it and got the root cause. We cannot use "checking-on" as the judgment, since 'ON' > can be cleared by hypervisor software in lots of places. In this case, KVM_REQ_EVENT cannot be > set when we check 'ON' bit, hence the interrupts are not injected to the guest in time. > > Please refer to the following code, in which 'ON' bit can be cleared: > > apic_find_highest_irr () --> vmx_sync_pir_to_irr () --> pi_test_and_clear_on() > > Searching from the code step by step, apic_find_highest_irr() can be called by many other guys. > > Thanks, Ok then, ignore my suggestion. Can you resend the latest version please ? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
