Re: Xen 4.18 pvshim console issue (with patch)

[Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>]

On Wed, Oct 18, 2023 at 11:44:22AM +0100, Andrew Cooper wrote:
> On 18/10/2023 11:38 am, Manuel Bouyer wrote:
> > Hello,
> > With Xen 4.18, a PV domain running under pvshim doesn't get console input.
> > This is because the domain id in pvshim isn't 0 (and on x86 max_init_domid 
> > is
> > hardwired to 0), so console_input_domain() will never select that domain
> > as input.
> > 
> > The attached patch fixes it by translating 0 to the real domain id for
> > pvshim, but there may be a better way to do this.
> > 
> 
> Thankyou for the report.
> 
> First, CC'ing Henry as 4.18 release manager.
> 
> There have been changes in how this works recently in 4.18, notably c/s
> c2581c58bec96.

Yes, it looks like this one introduced the problem.
Before this, we would switch console_rx to 1 without checking if
domain (console_rx - 1) exists, and console_rx == 1 is a special case
in __serial_rx()

> 
> However, it's not obvious whether this worked in 4.17 or not.  i.e.
> whether it's a regression in 4.18, or whether it's been broken since PV
> Shim was introduced.

I don't know for 4.16 or 4.17 but I can tell that it's working in 4.15

-- 
Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
     NetBSD: 26 ans d'experience feront toujours la difference
--