From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.windriver.com (mail.windriver.com [147.11.1.11]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mail.windriver.com", Issuer "Intel External Basic Issuing CA 3A" (not verified)) by ozlabs.org (Postfix) with ESMTPS id D51ED2C00DC for ; Thu, 9 May 2013 19:45:04 +1000 (EST) Message-ID: <518B7014.1090508@windriver.com> Date: Thu, 9 May 2013 17:44:52 +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> In-Reply-To: <6A3DF150A5B70D4F9B66A25E3F7C888D0700E64A@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 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 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. > -> 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. Additionally, ret_from_except probably check to replay all. Tiejun