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hvc/xen: fix event channel handling for secondary consoles

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The xencons_connect_backend() function allocates a local interdomain
event channel with xenbus_alloc_evtchn(), then calls
bind_interdomain_evtchn_to_irq_lateeoi() to bind to that port# on the
*remote* domain.

That doesn't work very well:

(qemu) device_add xen-console,id=con1,chardev=pty0
[   44.323872] xenconsole console-1: 2 xenbus_dev_probe on device/console/1
[   44.323995] xenconsole: probe of console-1 failed with error -2

Fix it to use bind_evtchn_to_irq_lateeoi(), which does the right thing
by just binding that *local* event channel to an irq. The backend will
do the interdomain binding.

This didn't affect the primary console because the setup for that is
special — the toolstack allocates the guest event channel and the guest
discovers it with HVMOP_get_param.

Fixes: fe415186b4 ("xen/console: harden hvc_xen against event channel storms")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20231020161529.355083-2-dwmw2@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
David Woodhouse 2023-10-20 17:15:27 +01:00 committed by Greg Kroah-Hartman
parent 37058fd5d2
commit ef5dd8ec88
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/hvc/hvc_xen.c
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@ -433,7 +433,7 @@ static int xencons_connect_backend(struct xenbus_device *dev,
if (ret)
return ret;
info->evtchn = evtchn;
irq = bind_interdomain_evtchn_to_irq_lateeoi(dev, evtchn);
irq = bind_evtchn_to_irq_lateeoi(evtchn);
if (irq < 0)
return irq;
info->irq = irq;