Re: [Xen-devel] pv-grub guest booting fail with recent qemu-xen

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Mar 30, 2016 at 02:05:28AM +0000, Hao, Xudong wrote:
> > -----Original Message-----
> > From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx]
> > Sent: Wednesday, March 30, 2016 12:58 AM
> > To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: Hao, Xudong <xudong.hao@xxxxxxxxx>; wei.liu2@xxxxxxxxxx;
> > samuel.thibault@xxxxxxxxxxxx; stefano.stabellini@xxxxxxxxxxxxx; xen-
> > devel@xxxxxxxxxxxxx
> > Subject: Re: [Xen-devel] pv-grub guest booting fail with recent qemu-xen
> > 
> > On Mon, Mar 28, 2016 at 09:21:14AM -0400, Konrad Rzeszutek Wilk wrote:
> > > On Mon, Mar 28, 2016 at 02:03:35AM +0000, Hao, Xudong wrote:
> > > > > -----Original Message-----
> > > > > From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf
> > > > > Of Konrad Rzeszutek Wilk
> > > > > Sent: Saturday, March 26, 2016 2:58 AM
> > > > > To: Hao, Xudong <xudong.hao@xxxxxxxxx>
> > > > > Cc: stefano.stabellini@xxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx
> > > > > Subject: Re: [Xen-devel] pv-grub guest booting fail with recent
> > > > > qemu-xen
> > > > >
> > > > > On Wed, Mar 02, 2016 at 07:16:40AM +0000, Hao, Xudong wrote:
> > > > > > Hi,
> > > > > > For Xen upstream master branch with commit 1949868d, After
> > > > > > updating qemu-
> > > > > xen version from fcf6ac57 to 2ce1d30e, booting a pv-grub guest will 
> > > > > fail.
> > >
> > 
> > pv-grub should be using qemu-traditional, not qemu-xen
> > 
> 
> Never hear this limitation.
> 
> > The log message you posted in your original post doesn't seem to reveal 
> > much.
> > Can you have a look at relevant QEMU logs under /var/log/xen?
> 
> There is not valuable qemu log, only one line: "qemu: terminating on signal 1 
> from pid 36642".
> 
> Bisect and the bad commit of qemu-xen is:

If you use PV-grub without the framebuffer does it boot?


> 
> commit 2ce1d30ef2858dfed72a281872579e5a26b090dd
> Author: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> Date:   Wed Jan 6 16:32:22 2016 +0000
> 
>     xenfb.c: avoid expensive loops when prod <= out_cons
> 
>     If the frontend sets out_cons to a value higher than out_prod, it will
>     cause xenfb_handle_events to loop about 2^32 times. Avoid that by using
>     better checks at the beginning of the function.
> 
>     upstream-commit-id: ac0487e1d2ae811cd4d035741a109a4ecfb013f1
> 
>     Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>     Reported-by: Ling Liu <liuling-it@xxxxxx>
> 
> diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
> index 4e2a27a..8eb3046 100644
> --- a/hw/display/xenfb.c
> +++ b/hw/display/xenfb.c
> @@ -789,8 +789,9 @@ static void xenfb_handle_events(struct XenFB *xenfb)
> 
>      prod = page->out_prod;
>      out_cons = page->out_cons;
> -    if (prod == out_cons)
> -       return;
> +    if (prod - out_cons >= XENFB_OUT_RING_LEN) {
> +        return;
> +    }
>      xen_rmb();         /* ensure we see ring contents up to prod */
>      for (cons = out_cons; cons != prod; cons++) {
>         union xenfb_out_event *event = &XENFB_OUT_RING_REF(page, cons);
> 

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