> -----Original Message----- > From: tiejun.chen [mailto:tiejun.c...@windriver.com] > Sent: Thursday, May 09, 2013 3:15 PM > To: Bhushan Bharat-R65777 > Cc: Caraman Mihai Claudiu-B02008; Wood Scott-B07421; linuxppc- > d...@lists.ozlabs.org; ag...@suse.de; kvm-...@vger.kernel.org; > k...@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....@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; ag...@suse.de; > >> kvm-...@vger.kernel.org; k...@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. > > > -> 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? > > Additionally, ret_from_except probably check to replay all. Local_irq_enable() will not take us to ret_from_except. -Bharat > > Tiejun _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
