From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Subject: Re: [PATCH] KVM: PPC: Book3E 64: Fix IRQs warnings and hangs Date: Fri, 3 May 2013 17:06:48 -0500 Message-ID: <1367618808.19391.11@snotra> References: <300B73AA675FCE4A93EB4FC1D42459FF3E9B37@039-SN2MPN1-013.039d.mgd.msft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; delsp=Yes; format=Flowed Content-Transfer-Encoding: 8BIT Cc: Wood Scott-B07421 , "kvm-ppc@vger.kernel.org" , "kvm@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" To: Caraman Mihai Claudiu-B02008 Return-path: In-Reply-To: <300B73AA675FCE4A93EB4FC1D42459FF3E9B37@039-SN2MPN1-013.039d.mgd.msft.net> (from B02008@freescale.com on Fri May 3 15:56:47 2013) Content-Disposition: inline Sender: kvm-ppc-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 05/03/2013 03:56:47 PM, Caraman Mihai Claudiu-B02008 wrote: > > -----Original Message----- > > From: Wood Scott-B07421 > > Sent: Friday, May 03, 2013 11:15 PM > > To: Caraman Mihai Claudiu-B02008 > > Cc: Wood Scott-B07421; kvm-ppc@vger.kernel.org; kvm@vger.kernel.org; > > linuxppc-dev@lists.ozlabs.org > > Subject: Re: [PATCH] KVM: PPC: Book3E 64: Fix IRQs warnings and > hangs > > > > > > > The unresponsiveness has to do with the fact that > > > > > arch_local_irq_restore() > > > > > does not guarantees to hard enable interrupts. > > > > > > > > Could you elaborate? If the saved IRQ state was "enabled", why > > > > wouldn't arch_local_irq_restore() hard-enable IRQs? The last > thing > > > it > > > > does is __hard_irq_enable(). > > > > > > if (!irq_happened) > > > return; > > > > OK, so the problem is that we're not setting PACA_IRQ_HARD_DIS when > we > > hard-disable interrupts? > > We enter guest with local_irq_disable() which means soft disabled, Hmm... I don't see any obvious breakage from that, but it makes me nervous. I'd be more comfortable if we just hard-disabled interrupts there. > when do we hard-disable interrupts? Interrupts will be hard-disabled when we take an exception to exit guest state. > If we follow host exception handlers model > they set PACA_IRQ_EE/DEC/DBELL but not PACA_IRQ_HARD_DIS. Can you > give it > a try to see how KVM behaves with PACA_IRQ_HARD_DIS? I can't do it > right now. I replaced the two calls to kvmppc_lazy_ee_enable() with calls to hard_irq_disable(), and it seems to be working fine. > > > > Where is the arch_local_irq_restore() instance you're talking > about? > > > > > > ./arch/power/kernel/irq.c > > > > I meant the caller. :-P > > ./arch/powerpc/include/asm/hw_irq.h > > 55static inline unsigned long arch_local_irq_disable(void) > 56{ > 57 unsigned long flags, zero; > 58 > 59 asm volatile( > 60 "li %1,0; lbz %0,%2(13); stb %1,%2(13)" > 61 : "=r" (flags), "=&r" (zero) > 62 : "i" (offsetof(struct paca_struct, soft_enabled)) > 63 : "memory"); > 64 > 65 return flags; > 66} > 67 > 68extern void arch_local_irq_restore(unsigned long); > 69 > 70static inline void arch_local_irq_enable(void) > 71{ > 72 arch_local_irq_restore(1); > 73} Sigh. I meant the real caller, who's calling local_irq_restore(). -Scott