On Tue, Apr 14, 2015 at 07:37:44AM +0000, Wu, Feng wrote: > > > > -----Original Message----- > > From: Marcelo Tosatti [mailto:mtosa...@redhat.com] > > Sent: Tuesday, March 31, 2015 7:56 AM > > To: Wu, Feng > > Cc: h...@zytor.com; t...@linutronix.de; mi...@redhat.com; x...@kernel.org; > > g...@kernel.org; pbonz...@redhat.com; dw...@infradead.org; > > j...@8bytes.org; alex.william...@redhat.com; jiang....@linux.intel.com; > > eric.au...@linaro.org; linux-kernel@vger.kernel.org; > > io...@lists.linux-foundation.org; k...@vger.kernel.org > > 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:mtosa...@redhat.com] > > > > Sent: Saturday, March 28, 2015 3:30 AM > > > > To: Wu, Feng > > > > Cc: h...@zytor.com; t...@linutronix.de; mi...@redhat.com; > > x...@kernel.org; > > > > g...@kernel.org; pbonz...@redhat.com; dw...@infradead.org; > > > > j...@8bytes.org; alex.william...@redhat.com; jiang....@linux.intel.com; > > > > eric.au...@linaro.org; linux-kernel@vger.kernel.org; > > > > io...@lists.linux-foundation.org; k...@vger.kernel.org > > > > 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 linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
