Re: [PATCH v2] xen/hvc: replace BUG_ON() with negative return value

On 07.07.21 11:57, Jan Beulich wrote:

On 07.07.2021 11:10, Juergen Gross wrote:

quoted

Xen frontends shouldn't BUG() in case of illegal data received from
their backends. So replace the BUG_ON()s when reading illegal data from
the ring page with negative return values.

Signed-off-by: Juergen Gross <jgross@suse.com>

Reviewed-by: Jan Beulich <redacted>

quoted

--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c

@@ -86,7 +86,11 @@ static int __write_console(struct xencons_info *xencons,
  	cons = intf->out_cons;
  	prod = intf->out_prod;
  	mb();			/* update queue values before going on */

Largely unrelated note: While in general the barriers here may want
switching to virt_*mb(), this particular one looks to be too heavy
anyway: a read barrier is all that's needed here afaict, just like
there's only a write barrier between ring contents and producer
writing in __write_console().

I agree.

And btw, since I've got puzzled by the linuxppc-dev@ in the recipients
list, I did look up relevant entries in ./MAINTAINERS. Shouldn't the
file be part of "XEN HYPERVISOR INTERFACE"?

I wouldn't mind. Greg, Jiri, what do you think?


Juergen