> -----Original Message----- > From: tiejun.chen [mailto:tiejun.c...@windriver.com] > Sent: Thursday, May 09, 2013 3:48 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 06:00 PM, Bhushan Bharat-R65777 wrote: > > > > > >> -----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. > > 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 :)
__replay_interrupt() from arch_local_irq_enable() will take us to ret_from_except/lite :) There all pending interrupts are replayed one by one before we hard-enable and soft-enable interrupts. -Bharat > > Tiejun _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
