Re: [XTF 3/4] Enabled serial writing for hvm guests

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/04/2020 12:44, Wieczorkiewicz, Pawel wrote:
>>> +}
>>> +
>>> static void xen_console_write(const char *buf, size_t len)
>>> {
>>>     hypercall_console_write(buf, len);
>>> @@ -246,7 +253,14 @@ static void xen_console_write(const char *buf, size_t 
>>> len)
>>> void arch_setup(void)
>>> {
>>>     if ( IS_DEFINED(CONFIG_HVM) && !pvh_start_info )
>>> +    {
>>>         register_console_callback(qemu_console_write);
>>> +    }
>>> +
>>> +    if ( IS_DEFINED(CONFIG_HVM) )
>>> +    {
>>> +        register_console_callback(com1_write);
>> This wires up 0x3f8 even for PVH guests, which I'm guessing isn't
>> intentional?  This should be part of the previous if(), but does beg the
>> question what is wrong with the existing qemu console?
>>
> It turns out that both PVH and HVM guests are PVH ABI compatible,

Correct

> but PVH does not need qemu console.

Its not that.  PVH guests are intended to run without qemu so there is
nothing listening on port 0x12.

> In order to get serial console via qemu working, I always register com1
> handler for both HVM and PVH. Register qemu console only for HVM guests.

> I use the com1 to make qemu write console output to a file via: 
> serial=“file:/tmp/…”


Right, but this is a local configuration issue.

I'm happy to make console selection more flexible, but there is
absolutely no need to two separate IO ports throwing the same text
string at Qemu.

~Andrew