On 2018-04-24 15:39, [email protected] wrote:
> Hi,
> 
> Using the jailhouse console from an inmate requires the cell config to
> have the JAILHOUSE_CELL_DEBUG_CONSOLE flag set. If it does not, all
> output is silently dropped.
> 
> Adding a jailhouse console message stating that an inmate has been
> blocked accessing the console is a nice to have from a developer
> standpoint but not that useful in production.
> 
> Is it worth issuing this notification?

Doable, it's just a bit of "warning: you have debugging disabled".

> If so, is it a good idea to have a "DEBUG" version of jailhouse to
> activate it?
> It looks like there will be a need for warn_once flags in the cell
> definition as we just want to warn once, not for every character sent
> via the hypercall.

Well... we could attach it to CONFIG_TRACE_ERROR:

diff --git a/hypervisor/control.c b/hypervisor/control.c
index 858ffc745..5cf96c951 100644
--- a/hypervisor/control.c
+++ b/hypervisor/control.c
@@ -876,7 +876,7 @@ long hypercall(unsigned long code, unsigned long
arg1, unsigned long arg2)
        case JAILHOUSE_HC_DEBUG_CONSOLE_PUTC:
                if (!(cpu_data->cell->config->flags &
                      JAILHOUSE_CELL_DEBUG_CONSOLE))
-                       return -EPERM;
+                       return trace_error(-EPERM);
                printk("%c", (char)arg1);
                return 0;
        default:

That won't be warn_once, but it's really simple.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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