From: Wei Liu <wei.liu2@citrix.com>
To: Samuel Thibault <samuel.thibault@ens-lyon.org>,
Wei Liu <wei.liu2@citrix.com>,
"Hao, Xudong" <xudong.hao@intel.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
"stefano.stabellini@eu.citrix.com"
<stefano.stabellini@eu.citrix.com>,
Anthony PERARD <anthony.perard@citrix.com>
Subject: Re: pv-grub guest booting fail with recent qemu-xen
Date: Mon, 11 Apr 2016 11:54:06 +0100 [thread overview]
Message-ID: <20160411105406.GC1346@citrix.com> (raw)
In-Reply-To: <20160410201446.GN2992@var.home>
On Sun, Apr 10, 2016 at 10:14:46PM +0200, Samuel Thibault wrote:
> 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.
>
OK, thanks for checking!
Hudong, can you try the following diff?
diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
index 8eb3046..284b345 100644
--- a/hw/display/xenfb.c
+++ b/hw/display/xenfb.c
@@ -789,7 +789,7 @@ static void xenfb_handle_events(struct XenFB *xenfb)
prod = page->out_prod;
out_cons = page->out_cons;
- if (prod - out_cons >= XENFB_OUT_RING_LEN) {
+ if (prod - out_cons > XENFB_OUT_RING_LEN) {
return;
}
xen_rmb(); /* ensure we see ring contents up to prod */
> Samuel
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next prev parent reply other threads:[~2016-04-11 10:54 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
2016-04-11 10:54 ` Wei Liu [this message]
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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