RE: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable interrupts - Bhushan Bharat-R65777

From: Bhushan Bharat-R65777 <R65777@freescale.com>
To: tiejun.chen <tiejun.chen@windriver.com>
Cc: Caraman Mihai Claudiu-B02008 <B02008@freescale.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Wood Scott-B07421 <B07421@freescale.com>,
	"agraf@suse.de" <agraf@suse.de>,
	"kvm-ppc@vger.kernel.org" <kvm-ppc@vger.kernel.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: RE: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable interrupts
Date: Thu, 9 May 2013 07:51:09 +0000	[thread overview]
Message-ID: <6A3DF150A5B70D4F9B66A25E3F7C888D0700E563@039-SN2MPN1-011.039d.mgd.msft.net> (raw)
In-Reply-To: <518B54A6.1070505@windriver.com>

> -----Original Message-----
> From: tiejun.chen [mailto:tiejun.chen@windriver.com]
> Sent: Thursday, May 09, 2013 1:18 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 03:33 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).
> >
> > Embedded Perfmon interrupt is also asynchronous, Why that is not in the list
> of masked interruts.
> 
> Are you saying perfmon? If so, its also in that list:
> 
>          START_EXCEPTION(perfmon);
>          NORMAL_EXCEPTION_PROLOG(0x260, BOOKE_INTERRUPT_PERFORMANCE_MONITOR,
>                                  PROLOG_ADDITION_NONE)
>          EXCEPTION_COMMON(0x260, PACA_EXGEN, INTS_DISABLE)

Where it is recorded in paca->irq_happned to be replayed later ?

> 
> Tiejun
> 
> >
> > -Bharat
> >
> >> 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.
> >>
> >> -Mike
> 