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From: Samuel Thibault <samuel.thibault@ens-lyon.org>
To: Wei Liu <wei.liu2@citrix.com>
Cc: Anthony PERARD <anthony.perard@citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	"Hao, Xudong" <xudong.hao@intel.com>,
	"stefano.stabellini@eu.citrix.com"
	<stefano.stabellini@eu.citrix.com>
Subject: Re: pv-grub guest booting fail with recent qemu-xen
Date: Sun, 10 Apr 2016 22:14:46 +0200	[thread overview]
Message-ID: <20160410201446.GN2992@var.home> (raw)
In-Reply-To: <20160405154108.GF18120@citrix.com>

Hello,

> > > > +    if (prod - out_cons >= XENFB_OUT_RING_LEN) {
> > > > +        return;
> > > > +    }

This test seems overzealous to me: AIUI, the producer can produce
XENFB_OUT_RING_LEN events, and thus prod - out_cons is exactly
XENFB_OUT_RING_LEN, i.e. there is no room left at all.

The frontend part is:

   while (page->out_prod - page->out_cons == XENFB_OUT_RING_LEN)
        schedule();

I.e. it waits while the buffer is exactly full.

So it seems to me the bug is at the backend side.

Samuel

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  reply	other threads:[~2016-04-10 20:14 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-02  7:16 pv-grub guest booting fail with recent qemu-xen Hao, Xudong
2016-03-25 18:57 ` Konrad Rzeszutek Wilk
2016-03-28  2:03   ` Hao, Xudong
2016-03-28 13:21     ` Konrad Rzeszutek Wilk
2016-03-29  1:44       ` Hao, Xudong
2016-03-29 16:58       ` Wei Liu
2016-03-30  2:05         ` Hao, Xudong
2016-04-01 15:54           ` Konrad Rzeszutek Wilk
2016-04-05  1:26             ` Hao, Xudong
2016-04-05 15:41               ` Wei Liu
2016-04-10 20:14                 ` Samuel Thibault [this message]
2016-04-11 10:54                   ` Wei Liu
2016-04-11 11:52                     ` Wei Liu
2016-04-12  1:56                     ` Hao, Xudong
2016-04-12  8:28                       ` Wei Liu

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