From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail1.windriver.com (mail1.windriver.com [147.11.146.13]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mail1.windriver.com", Issuer "Intel External Basic Issuing CA 3A" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 123372C00E2 for ; Thu, 9 May 2013 20:18:25 +1000 (EST) Message-ID: <518B77E5.9020809@windriver.com> Date: Thu, 9 May 2013 18:18:13 +0800 From: "tiejun.chen" MIME-Version: 1.0 To: Bhushan Bharat-R65777 Subject: Re: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable interrupts References: <51885F49.6060605@windriver.com> (from tiejun.chen@windriver.com on Mon May 6 20:56:25 2013) <1367892390.3398.12@snotra> <300B73AA675FCE4A93EB4FC1D42459FF3F00D0@039-SN2MPN1-013.039d.mgd.msft.net> <6A3DF150A5B70D4F9B66A25E3F7C888D0700E64A@039-SN2MPN1-011.039d.mgd.msft.net> <518B7014.1090508@windriver.com> <6A3DF150A5B70D4F9B66A25E3F7C888D0700E85D@039-SN2MPN1-011.039d.mgd.msft.net> In-Reply-To: <6A3DF150A5B70D4F9B66A25E3F7C888D0700E85D@039-SN2MPN1-011.039d.mgd.msft.net> Content-Type: text/plain; charset="UTF-8"; format=flowed Cc: Caraman Mihai Claudiu-B02008 , "kvm@vger.kernel.org" , Wood Scott-B07421 , "agraf@suse.de" , "kvm-ppc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 05/09/2013 06:00 PM, Bhushan Bharat-R65777 wrote: > > >> -----Original Message----- >> From: tiejun.chen [mailto:tiejun.chen@windriver.com] >> Sent: Thursday, May 09, 2013 3:15 PM >> To: Bhushan Bharat-R65777 >> Cc: Caraman Mihai Claudiu-B02008; Wood Scott-B07421; linuxppc- >> dev@lists.ozlabs.org; agraf@suse.de; kvm-ppc@vger.kernel.org; >> kvm@vger.kernel.org >> Subject: Re: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable interrupts >> >> On 05/09/2013 04:23 PM, Bhushan Bharat-R65777 wrote: >>> >>> >>>> -----Original Message----- >>>> From: Linuxppc-dev [mailto:linuxppc-dev- >>>> bounces+bharat.bhushan=freescale.com@lists.ozlabs.org] On Behalf Of >>>> bounces+Caraman >>>> Mihai Claudiu-B02008 >>>> Sent: Wednesday, May 08, 2013 6:44 PM >>>> To: Wood Scott-B07421; tiejun.chen >>>> Cc: linuxppc-dev@lists.ozlabs.org; agraf@suse.de; >>>> kvm-ppc@vger.kernel.org; kvm@vger.kernel.org >>>> Subject: RE: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable >>>> interrupts >>>> >>>>>> This only disable soft interrupt for kvmppc_restart_interrupt() >>>>>> that restarts interrupts if they were meant for the host: >>>>>> >>>>>> a. SOFT_DISABLE_INTS() only for BOOKE_INTERRUPT_EXTERNAL | >>>>>> BOOKE_INTERRUPT_DECREMENTER | BOOKE_INTERRUPT_DOORBELL >>>>> >>>>> Those aren't the only exceptions that can end up going to the host. >>>>> We could get a TLB miss that results in a heavyweight MMIO exit, etc. >>>>> >>>>>> And shouldn't we handle kvmppc_restart_interrupt() like the >>>>>> original HOST flow? >>>>>> >>>>>> #define MASKABLE_EXCEPTION(trapnum, intnum, label, hdlr, >>>>>> ack) \ >>>>>> >>>>>> START_EXCEPTION(label); \ >>>>>> NORMAL_EXCEPTION_PROLOG(trapnum, intnum, >>>>>> PROLOG_ADDITION_MASKABLE)\ >>>>>> EXCEPTION_COMMON(trapnum, PACA_EXGEN, >>>>>> *INTS_DISABLE*) \ >>>>>> ... >>>>> >>>>> Could you elaborate on what you mean? >>>> >>>> I think Tiejun was saying that host has flags and replays only >>>> EE/DEC/DBELL interrupts. There is special macro >>>> masked_interrupt_book3e in those exception handlers that sets paca- >>> irq_happened. >>>> >>>> The list of replied interrupts is limited to asynchronous noncritical >>>> interrupts which can be masked by MSR[EE] (therefore no TLB miss). >>>> Now on KVM book3e we don't want to put them in the irq_happened lazy >>>> state but rather to execute them directly, so there is no reason for >>>> exception handling symmetry between host and guest. >>> >>> >>> Another Question: >>> >>> The case is: >>> >> >> Actually in the case GS=1 even if EE=0, EXT/DEC/DBELL still occur as I recall. >> >>> Case 1) >>> -> Local_irq_disable() will set soft_enabled = 0 >>> -> Now Externel interrupt happens, there we set PACA_IRQ_EE in irq_happened, >> Also clears EE in SRR1 and rfi. So interrupts are hard disabled. No more other >> interrupt gated by MSR.EE can happen. Looks like the idea here is to not let a >> device keep on inserting interrupt till the interrupt condition on device is >> cleared, right? >> >> I don't understand "the interrupt condition on device is cleared" here. >> >> I think regardless if you clear the device interrupt status, the system still >> receive a pending interrupt once EE or GS = 1. > > Once yes, but I think to avoid flood of device interrupt we disable MSR.EE when soft-disabled. But we neither ACK nor send EOI to that irq in the interrupt controller, so that should be in pending state. > >> >>> -> local_irq_enable() - This checks that irq_happened is set, and >>> replays >> >> ret_from_except also check to replay. >> >>> >>> Now the case 2) >>> Case 2) >>> -> Local_irq_disable() will set soft_enabled = 0 >>> -> Now DEC interrupt happens. We set PACA_IRQ_DEC in irq_happened, But do >> not clear EE in SRR1 and rfi. So interrupts are not hard disabled. >>> -> Now say EE interrupt happens, there we set PACA_IRQ_EE in irq_happened, >> Also clears EE in SRR1 and rfi. So interrupts are hard disabled. >>> -> local_irq_enable() - This checks that irq_happened is set. >>> IIUC, it replays only one interrupt? is not it? >> >> After anyone is replayed in arch_local_irq_restore(), we will set soft/hard >> interrupt there: >> >> set_soft_enabled(1); >> __hard_irq_enable(); >> >> Then any pending interrupt can be executed now. > > Do you mean that the interrupt should fire again? I means the pending exception including external interrupt, the decrementer exception and the doorbell exception, can trap CPU once EE=1 with __hard_irq_enable() here. Then the kernel can handle those exception since soft enable is also 1 now. > >> >> Additionally, ret_from_except probably check to replay all. > > Local_irq_enable() will not take us to ret_from_except. Yes. I just say ret_from_except can provide an approach to replay all :) Tiejun