On 06/22/2016 12:45 PM, Jim Fehlig wrote:
> On 06/22/2016 06:07 AM, Cole Robinson wrote:
>> On 06/21/2016 10:32 PM, Jim Fehlig wrote:
>>> On 06/21/2016 04:20 AM, Joao Martins wrote:
>>>> On 06/21/2016 01:38 AM, Jim Fehlig wrote:
>>>>> Joao Martins wrote:
>>>>>> Guests use a <console /> (and sometimes <serial /> pair) to represent
>>>>>> the console. On the callback that is called when console is brought up
>>>>>> (NB: before domain starts), we fill the path of the console element with
>>>>>> the appropriate "/dev/pts/X". For PV guests it all works fine, although
>>>>>> for HVM guests it doesn't. Consequently we end up seeing erronous
>>>>>> behaviour on HVM guests where console path is not displayed on the XML
>>>>>> but still can be accessed with virDomainOpenConsole after booting guest.
>>>>>> Consumers of this XML (e.g. Openstack) also won't be able to use the
>>>>>> console path.
>>>>> Can you provide example input domXML config that causes this problem?
>>>>>
>>>> Ah yes - I probably should include that in the commit description?
>>> Yes, I think it helps clarify the problem being solved by the commit.
>>>
>>>> So, for PV guests for an input console XML element:
>>>>
>>>> <console type='pty'>
>>>> <target type='xen' port='0'/>
>>>> </console>
>>>>
>>>> Which then on domain start gets filled like:
>>>>
>>>> <console type='pty' tty='/dev/pts/3'>
>>>> <source path='/dev/pts/3'/>
>>>> <target type='xen' port='0'/>
>>>> </console>
>>>>
>>>> Although for HVM guests we have:
>>>>
>>>> <serial type='pty'>
>>>> <target port='0'/>
>>>> </serial>
>>>> <console type='pty'>
>>>> <target type='serial' port='0'/>
>>>> </console>
>>>>
>>>> And no changes happen i.e. source path isn't written there _even though_ it's
>>>> set on the console element - being the reason why we can access the console in the
>>>> first place. IIUC The expected output should be:
>>>>
>>>> <serial type='pty'>
>>>> <source path='/dev/pts/4'/>
>>>> <target port='0'/>
>>>> </serial>
>>>> <console type='pty' tty='/dev/pts/4'>
>>>> <source path='/dev/pts/4'/>
>>>> <target type='serial' port='0'/>
>>>> </console>
>>> I asked for an example after having problems testing your patch, but it turned
>>> out to be an issue which I think was introduced long ago by commit 482e5f15. I
>>> was testing with transient domains and noticed 'virsh create; 'virsh console'
>>> always failed with
>>>
>>> error: internal error: character device <null> is not using a PTY
>>>
>>> My config only contained
>>>
>>> <console type='pty'>
>>> <target port='0'/>
>>> </console>
>>>
>>> so the "really crazy backcompat stuff for consoles" in
>>> virDomainDefAddConsoleCompat() moved the config over to def->serials[0] and
>>> created a new def->consoles[0] without def->consoles[0].source.type set to
>>> VIR_DOMAIN_CHR_TYPE_PTY. Without source.type set, libxlConsoleCallback() would
>>> ignore the console and not copy the PTY path to source.data.file.path. 'virsh
>>> console' would then fail with the error noted above.
>>>
>>> I spent too much time debugging this, partly because I was confused by odd
>>> behavior with persistent domains. E.g. 'virsh define; virsh start; virsh
>>> console' would fail with the same error, but all subsequent 'virsh shutdown;
>>> virsh start; virsh console' sequences would work :-). That behavior was due to
>>> vm->newDef being populated with correct console config when calling
>>> virDomainObjSetDefTransient() in libxlDomainStart(). After the first shutdown of
>>> the domain, vm->newDef would be copied over to vm->def, allowing subsequent
>>> 'virsh start; virsh console' to work correctly.
>>>
>> Hmm, that sounds weird. Can you explain more how exactly the XML changes?
>
> It only changes when defining the vm.
>
>> What
>> is the diff between the initial 'virsh define; virsh dumpxml'
>
> Initial XML has
>
> <console type='pty'>
> <target port='0'/>
> </console>
>
> After define
>
> <serial type='pty'>
> <target port='0'/>
> </serial>
> <console type='pty'>
> <target type='serial' port='0'/>
> </console>
>
> The config doesn't change after start; shutdown. But the contents of
> virDomainDef does change, specifically def->consoles[0]->source.type changes
> from VIR_DOMAIN_CHR_TYPE_PTY to VIR_DOMAIN_CHR_TYPE_NULL. And as mentioned
> below, libxlConsoleCallback() only checks for source.type ==
> VIR_DOMAIN_CHR_TYPE_PTY before copying the PTY path to
> def->consoles[0]->source.data.file.path. Another potential fix I also mentioned
> below is to loosen that condition in libxlConsoleCallback(). I.e. copy the path
> if source.type equals VIR_DOMAIN_CHR_TYPE_PTY or VIR_DOMAIN_CHR_TYPE_NULL (and
> perhaps VIR_DOMAIN_CHR_TYPE_FILE too?).
>
Okay I think I follow. The thing I was missing is that
virDomainDefAddConsoleCompat will alter ->def, but that's _not_ what is
formated/printed in the XML, which has some special handling to fully
duplicate serials[0] XML to consoles[0], if console target type=serial
I _think_ what the proper thing to do here is something like:
diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
index 221af87..6bcb4d9 100644
--- a/src/libxl/libxl_domain.c
+++ b/src/libxl/libxl_domain.c
@@ -964,13 +964,17 @@ libxlConsoleCallback(libxl_ctx *ctx, libxl_event *ev,
void *for_callback)
virObjectLock(vm);
for (i = 0; i < vm->def->nconsoles; i++) {
virDomainChrDefPtr chr = vm->def->consoles[i];
- if (chr && chr->source.type == VIR_DOMAIN_CHR_TYPE_PTY) {
+ if (i == 0 &&
+ chr->targetType == VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL)
+ chr = vm->def->serials[0];
+
+ if (chr->source.type == VIR_DOMAIN_CHR_TYPE_PTY) {
libxl_console_type console_type;
char *console = NULL;
int ret;
console_type =
- (chr->targetType == VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL ?
+ (chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_SERIAL ?
LIBXL_CONSOLE_TYPE_SERIAL : LIBXL_CONSOLE_TYPE_PV);
ret = libxl_console_get_tty(ctx, ev->domid,
chr->target.port, console_type,
Untested, but basically, libxl driver needs to learn that if
consoles[0].target.type == SERIAL, then you should use serials[0] instead. The
qemu driver has some magic like this sprinkled around...
The problem with your patch below is that it's not a whole fix, there's many
other bits besides source.type that would technically need to be copied over.
Rather than doing that, which has its own problems trying to keep the
console[0] and serial[0] data in sync, the convention seems to be that console
gets only target.type=serial and the drivers need to map that to serials[0].
That's my reading of things anyways
Thanks,
Cole
> Regards,
> Jim
>
>> and the dumpxml
>> after the VM has started+shutdown once? Whatever that diff is, and why it's
>> not in the XML to begin with, sounds like the root issue to me.
>>
>>> Long story short, I found the problem but not sure how to fix it :-). One
>>> approach would be the below patch. Another would be to loosen the restriction in
>>> libxlConsoleCallback, filing in source.data.file.path when the console source
>>> type is also set to VIR_DOMAIN_CHR_TYPE_NULL. Adding Cole and Peter (both of
>>> which have toiled in and likely loathe this code) to see if they have opinions
>>> on a proper fix.
>>>
>>> Regards,
>>> Jim
>>>
>>>
>>> From a231636e8eec08152220e32af5f4026a50954f41 Mon Sep 17 00:00:00 2001
>>> From: Jim Fehlig <jfehlig@xxxxxxxx>
>>> Date: Tue, 21 Jun 2016 20:25:23 -0600
>>> Subject: [PATCH] domain conf: copy source type from stolen console
>>>
>>> When domXML contains only <console type='pty'> and no corresponding
>>> <serial>, the console is "stolen" [1] and used as the first <serial>
>>> device. A new console is created as an alias to the first <serial>
>>> device, but missed copying some configuration such as the source
>>> 'type' attribute.
>>>
>>> [1] See comments associated with virDomainDefAddConsoleCompat() in
>>> $LIBVIRT-SRC/src/conf/domain_conf.c:
>>>
>>> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
>>> ---
>>> src/conf/domain_conf.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>>> index 75ad03f..2fda4fe 100644
>>> --- a/src/conf/domain_conf.c
>>> +++ b/src/conf/domain_conf.c
>>> @@ -3845,6 +3845,7 @@ virDomainDefAddConsoleCompat(virDomainDefPtr def)
>>> /* Create an console alias for the serial port */
>>> def->consoles[0]->deviceType = VIR_DOMAIN_CHR_DEVICE_TYPE_CONSOLE;
>>> def->consoles[0]->targetType =
>>> VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL;
>>> + def->consoles[0]->source.type = def->serials[0]->source.type;
>>> }
>>> } else if (def->os.type == VIR_DOMAIN_OSTYPE_HVM && def->nserials > 0 &&
>>> def->serials[0]->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_SERIAL &&
>>>
>> Then again this also seems okay to me, but it's concerning that I applied this
>> but it didn't cause the test suite to change at all.
>>
>> - Cole
>>
>
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