From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Fri, 22 May 2020 00:05:56 +0000
Subject: Re: [PATCH 0/3] sparc: port to copy_thread_tls() and struct kernel_clone_args
Message-Id: <20200522000556.GA3149788@ZenIV.linux.org.uk>
List-Id: <sparclinux.vger.kernel.org>
References: <20200512171527.570109-1-christian.brauner@ubuntu.com>
In-Reply-To: <20200512171527.570109-1-christian.brauner@ubuntu.com>
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To: sparclinux@vger.kernel.org

On Thu, May 21, 2020 at 09:23:50PM +0100, Al Viro wrote:
> On Thu, May 21, 2020 at 08:42:34PM +0100, Mark Cave-Ayland wrote:
> 
> > > Can you tell me a bit more about the host in terms of CPU and disk to help figure out
> > > what's going on?
> 
> phenom II X6 1100T (6-way 3.3GHz), 8Gb RAM (4Gb given to guest), WDC WD10EACS-00D
> disk (hdparm -tT gives
>  Timing cached reads:   6988 MB in  2.00 seconds = 3494.96 MB/sec
>  Timing buffered disk reads: 280 MB in  3.02 seconds =  92.75 MB/sec
> )
> 
> > One other thought I had is that somehow the IVEC IRQs are managing to be overwritten
> > on a faster host before being read by the guest. Does the following patch display the
> > FATAL message at the point where things hang?
> 
> > diff --git a/hw/pci-host/sabre.c b/hw/pci-host/sabre.c
> > index fae20ee97c..618ebd1300 100644
> > --- a/hw/pci-host/sabre.c
> > +++ b/hw/pci-host/sabre.c
> > @@ -63,6 +63,9 @@
> >  static inline void sabre_set_request(SabreState *s, unsigned int irq_num)
> >  {
> >      trace_sabre_set_request(irq_num);
> > +    if (s->irq_request != 0 && s->irq_request != NO_IRQ_REQUEST) {
> > +        fprintf(stderr, "FATAL: still waiting for IRQ %x, now %x\n", s->irq_request,
> > irq_num);
> > +    }
> >      s->irq_request = irq_num;
> >      qemu_set_irq(s->ivec_irqs[irq_num], 1);
> >  }
> 
> I have to go AFK right now, will test when I get back (should be about an
> hour or two)

Hang, nothing on stderr until killed, at which point it gave the expected
qemu-system-sparc64: terminating on signal 15 from pid 15917 (-bash)
IOW, stderr got flushed after hang - that fprintf simply has not triggered.