Using VMChannel to communicate with the host.

Using VMChannel to communicate with the host.

[Cam Macdonell]

Hi,

I'm trying to get a better understanding of VM-to-host communication 
that doesn't involve going over virtual networks.  I understand there 
are a couple of developments underway, but I just want to play around a 
better sense of things.   I think the current hypercall mechanism is the 
current way to do this using the -vmchannel option.  But, I'm not very 
experienced with PCI devices and their drivers so I need some help.  All 
I want to do is to communicate across a unix domain socket on the host. 
  Besides loading the hypercall module in the guest how do things needs 
to be configured on the host?

Is there a simple tutorial or just a webpage with examples for how to do 
this?

Thanks,
Cam

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Re: Using VMChannel to communicate with the host.

[Troy Benjegerdes]

On Fri, Sep 07, 2007 at 04:44:30PM -0600, Cam Macdonell wrote:
> 
> Hi,
> 
> I'm trying to get a better understanding of VM-to-host communication 
> that doesn't involve going over virtual networks.  I understand there 
> are a couple of developments underway, but I just want to play around a 
> better sense of things.   I think the current hypercall mechanism is the 
> current way to do this using the -vmchannel option.  But, I'm not very 
> experienced with PCI devices and their drivers so I need some help.  All 
> I want to do is to communicate across a unix domain socket on the host. 
>   Besides loading the hypercall module in the guest how do things needs 
> to be configured on the host?
> 
> Is there a simple tutorial or just a webpage with examples for how to do 
> this?

I'm going to suggest that a better way to do VM-to-host or VM-to-VM
communication would be to write an OpenFabrics (www.openfabrics.org)
driver that uses hypercalls. There is probably some gotcha I am not
aware of, but I think this would allow direct userspace to userspace
communication between a process running on a host, and a process running
on a VM, while still maintaining isolation.

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Re: Using VMChannel to communicate with the host.

[Dor Laor]

Troy Benjegerdes wrote:
> On Fri, Sep 07, 2007 at 04:44:30PM -0600, Cam Macdonell wrote:
>   
>> Hi,
>>
>> I'm trying to get a better understanding of VM-to-host communication 
>> that doesn't involve going over virtual networks.  I understand there 
>> are a couple of developments underway, but I just want to play around a 
>> better sense of things.   I think the current hypercall mechanism is the 
>> current way to do this using the -vmchannel option.  But, I'm not very 
>> experienced with PCI devices and their drivers so I need some help.  All 
>> I want to do is to communicate across a unix domain socket on the host. 
>>   Besides loading the hypercall module in the guest how do things needs 
>> to be configured on the host?
>>
>> Is there a simple tutorial or just a webpage with examples for how to do 
>> this?
>>     
>
> I'm going to suggest that a better way to do VM-to-host or VM-to-VM
> communication would be to write an OpenFabrics (www.openfabrics.org)
> driver that uses hypercalls. There is probably some gotcha I am not
> aware of, but I think this would allow direct userspace to userspace
> communication between a process running on a host, and a process running
> on a VM, while still maintaining isolation.
>
>   
Basically that's true but you need a host glue dirver to connect the two 
+ the hypercall implementation.
It can be easily added to KVM with a small cost.

BTW: does all windows guest will have the guest side driver implemented? 
Including XP, 2k, Vista?

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Re: Using VMChannel to communicate with the host.

[Dor Laor]

Cam Macdonell wrote:
> Hi,
>
> I'm trying to get a better understanding of VM-to-host communication 
> that doesn't involve going over virtual networks.  I understand there 
> are a couple of developments underway, but I just want to play around a 
> better sense of things.   I think the current hypercall mechanism is the 
> current way to do this using the -vmchannel option.  But, I'm not very 
> experienced with PCI devices and their drivers so I need some help.  All 
> I want to do is to communicate across a unix domain socket on the host. 
>   Besides loading the hypercall module in the guest how do things needs 
> to be configured on the host?
>
> Is there a simple tutorial or just a webpage with examples for how to do 
> this?
>
> Thanks,
> Cam
>   
I just tested it, it got a little deprecated over time since it call 
pci_module_init instead of pci_register_* and some more irq function 
deprecation.The sysfs interface in not complete and you can't read/write 
from the device.
The qemu parameters are -vmchannel di:2258,unix:/tmp/file,server
2258 is the vendor id for the device, you can use unix sockets ot even 
tcp for the host end.

In several week we'll publish better version of it. Maybe we'll publish 
a preview before.
-Dor

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Re: Using VMChannel to communicate with the host.

[Cam Macdonell]

Dor Laor wrote:
> I just tested it, it got a little deprecated over time since it call 
> pci_module_init instead of pci_register_* and some more irq function 
> deprecation.The sysfs interface in not complete and you can't read/write 
> from the device.
> The qemu parameters are -vmchannel di:2258,unix:/tmp/file,server
> 2258 is the vendor id for the device, you can use unix sockets ot even 
> tcp for the host end.
> 

Hi Dor,

Thanks, that got it up and running.  But in the hypercall.c code (from 
the git repo) there is a "hello host" message that looks like it should 
be written to the host.  How do I trigger that to be sent so my very 
simple "listening" program can read it?

Thanks,
Cam

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Re: Using VMChannel to communicate with the host.

[Dor Laor]

Cam Macdonell wrote:
>
> Dor Laor wrote:
> > I just tested it, it got a little deprecated over time since it call
> > pci_module_init instead of pci_register_* and some more irq function
> > deprecation.The sysfs interface in not complete and you can't read/write
> > from the device.
> > The qemu parameters are -vmchannel di:2258,unix:/tmp/file,server
> > 2258 is the vendor id for the device, you can use unix sockets ot even
> > tcp for the host end.
> >
>
> Hi Dor,
>
> Thanks, that got it up and running.  But in the hypercall.c code (from
> the git repo) there is a "hello host" message that looks like it should
> be written to the host.  How do I trigger that to be sent so my very
> simple "listening" program can read it?
>
> Thanks,
> Cam
>
You need to open the unix socket you passed to the vmchannel parameter.
An easier alternative is to use -vmchannel di:2258,tcp://0:4444,server.
Before the guest loads you'll need to telnet the 4444 port and then you 
should receive the
hello world output once the driver is up.
-Dor

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Re: Using VMChannel to communicate with the host.

[Cameron Macdonell]

On 11-Sep-07, at 1:09 AM, Dor Laor wrote:

> Cam Macdonell wrote:
>>
>> Dor Laor wrote:
>> > I just tested it, it got a little deprecated over time since it  
>> call
>> > pci_module_init instead of pci_register_* and some more irq  
>> function
>> > deprecation.The sysfs interface in not complete and you can't  
>> read/write
>> > from the device.
>> > The qemu parameters are -vmchannel di:2258,unix:/tmp/file,server
>> > 2258 is the vendor id for the device, you can use unix sockets  
>> ot even
>> > tcp for the host end.
>> >
>>
>> Hi Dor,
>>
>> Thanks, that got it up and running.  But in the hypercall.c code  
>> (from
>> the git repo) there is a "hello host" message that looks like it  
>> should
>> be written to the host.  How do I trigger that to be sent so my very
>> simple "listening" program can read it?
>>
>> Thanks,
>> Cam
>>
> You need to open the unix socket you passed to the vmchannel  
> parameter.
> An easier alternative is to use -vmchannel di:2258,tcp:// 
> 0:4444,server.
> Before the guest loads you'll need to telnet the 4444 port and then  
> you should receive the
> hello world output once the driver is up.
> -Dor

I tried having a program listening on the unix domain socket.   
Actually, the VM won't even start until a program connects to the  
socket.  I didn't get the message with my listening program, but I'll  
try the telnet method as I haven't programmed a socket in a while so  
I may have missed a step.

While getting this working is novel to me, it seems from your email  
that not much can be done with the hypercall interface in terms of  
host-VM or VM-to-VM communication, correct?  If reading and writing  
don't work, how can one exchange info between VMs?  I'll look forward  
to the virtIO implementation.

Thanks,
Cam

-----------------------------------------------
A. Cameron Macdonell
Ph.D. Student
Department of Computing Science
University of Alberta
cam-edFDblaTWIyXbbII50Afww@public.gmane.org




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Re: Using VMChannel to communicate with the host.

[Dor Laor]

>> You need to open the unix socket you passed to the vmchannel
>> parameter.
>> An easier alternative is to use -vmchannel di:2258,tcp://
>> 0:4444,server.
>> Before the guest loads you'll need to telnet the 4444 port and then
>> you should receive the
>> hello world output once the driver is up.
>> -Dor
>
>I tried having a program listening on the unix domain socket.
>Actually, the VM won't even start until a program connects to the
>socket.  I didn't get the message with my listening program, but I'll
>try the telnet method as I haven't programmed a socket in a while so
>I may have missed a step.

Go for it, its 1 minute effort.

>While getting this working is novel to me, it seems from your email
>that not much can be done with the hypercall interface in terms of
>host-VM or VM-to-VM communication, correct?  If reading and writing
>don't work, how can one exchange info between VMs?  I'll look forward
>to the virtIO implementation.
>

The vmchannel was not intended to VM-to-VM networking, although it can
work.
Next version will be better. Anyway, it should have similar performance
to pv network driver.

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Re: Using VMChannel to communicate with the host.

[Cam Macdonell]

Dor Laor wrote:
>>> You need to open the unix socket you passed to the vmchannel
>>> parameter.
>>> An easier alternative is to use -vmchannel di:2258,tcp://
>>> 0:4444,server.
>>> Before the guest loads you'll need to telnet the 4444 port and then
>>> you should receive the
>>> hello world output once the driver is up.
>>> -Dor
>> I tried having a program listening on the unix domain socket.
>> Actually, the VM won't even start until a program connects to the
>> socket.  I didn't get the message with my listening program, but I'll
>> try the telnet method as I haven't programmed a socket in a while so
>> I may have missed a step.
> 
> Go for it, its 1 minute effort.

Hi Dor,

It didn't work.  I used the following option: -vmchannel 
di:2258,tcp:0:4444,server (the // confused kvm) and when the VM booted, 
I connected with "telnet localhost 4444" which allowed the boot to 
proceed.  But, I didn't get the hello host message when I loaded the 
hypercall module.  dmesg did show that the module loaded successfully. 
I'll dig around with it and see what else I can figure out

> 
>> While getting this working is novel to me, it seems from your email
>> that not much can be done with the hypercall interface in terms of
>> host-VM or VM-to-VM communication, correct?  If reading and writing
>> don't work, how can one exchange info between VMs?  I'll look forward
>> to the virtIO implementation.
>>
> 
> The vmchannel was not intended to VM-to-VM networking, although it can
> work.
> Next version will be better. Anyway, it should have similar performance
> to pv network driver.

Cool.

Thanks,
Cam

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Re: Using VMChannel to communicate with the host.

[Dor Laor]

[-- Attachment #1.1: Type: text/plain, Size: 1267 bytes --]

Cam Macdonell wrote:
>
> Dor Laor wrote:
> >>> You need to open the unix socket you passed to the vmchannel
> >>> parameter.
> >>> An easier alternative is to use -vmchannel di:2258,tcp://
> >>> 0:4444,server.
> >>> Before the guest loads you'll need to telnet the 4444 port and then
> >>> you should receive the
> >>> hello world output once the driver is up.
> >>> -Dor
> >> I tried having a program listening on the unix domain socket.
> >> Actually, the VM won't even start until a program connects to the
> >> socket.  I didn't get the message with my listening program, but I'll
> >> try the telnet method as I haven't programmed a socket in a while so
> >> I may have missed a step.
> >
> > Go for it, its 1 minute effort.
>
> Hi Dor,
>
> It didn't work.  I used the following option: -vmchannel
> di:2258,tcp:0:4444,server (the // confused kvm) and when the VM booted,
> I connected with "telnet localhost 4444" which allowed the boot to
> proceed.  But, I didn't get the hello host message when I loaded the
> hypercall module.  dmesg did show that the module loaded successfully.
> I'll dig around with it and see what else I can figure ou
>
I just tried it and it worked. I used fc7 2.6.21 kernel, 64 bits  for 
the guest.
Can you send the relevant dmesg?

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Re: Using VMChannel to communicate with the host.

[Cameron Macdonell]

On 15-Sep-07, at 4:47 PM, Dor Laor wrote:

> Cam Macdonell wrote:
>> It didn't work.  I used the following option: -vmchannel
>> di:2258,tcp:0:4444,server (the // confused kvm) and when the VM  
>> booted,
>> I connected with "telnet localhost 4444" which allowed the boot to
>> proceed.  But, I didn't get the hello host message when I loaded the
>> hypercall module.  dmesg did show that the module loaded  
>> successfully.
>> I'll dig around with it and see what else I can figure ou
>>
> I just tried it and it worked. I used fc7 2.6.21 kernel, 64 bits   
> for the guest.
> Can you send the relevant dmesg?

Here is the dmesg output within the guest.  I am running KVM-39 on  
Ubuntu 2.6.20 kernel, 32 bit for both
host and guest.

[  540.144000] Qumranet_hypercall_driver
[  540.148000] pci dev 0000:00:04.0 (id 5002:2258 rev 00) is a guest  
hypercall device
[  540.148000] PCI: Found IRQ 9 for device 0000:00:04.0
[  540.148000] hypercall_init_board: PIO region size == 0x100
[  540.148000] hypercall_init_board: MMIO region size == 0x00
[  540.148000] name=: base_addr=0xc200, io_addr=0x1c200, IRQ=9

For what it's worth, I can compile the driver/hypercall.c file that  
comes with kvm-39.  However, I can't compile your hypercall.c  
implementation, I get the following error:

make -C /lib/modules/2.6.20-16-generic/build M=`pwd` "$@"
make[1]: Entering directory `/usr/src/linux-headers-2.6.20-16-generic'
   CC [M]  /home/kvm/kvm-userspace/drivers/hypercall.o
/home/kvm/kvm-userspace/drivers/hypercall.c: In function  
‘hypercall_do_tasklet’:
/home/kvm/kvm-userspace/drivers/hypercall.c:226: error: invalid  
lvalue in unary ‘&’
/home/kvm/kvm-userspace/drivers/hypercall.c:226: error: invalid  
lvalue in unary ‘&’
/home/kvm/kvm-userspace/drivers/hypercall.c:231: warning: implicit  
declaration of function ‘hypercall_tx’
/home/kvm/kvm-userspace/drivers/hypercall.c: At top level:
/home/kvm/kvm-userspace/drivers/hypercall.c:236: error: static  
declaration of ‘hypercall_tx’ follows non-static declaration
/home/kvm/kvm-userspace/drivers/hypercall.c:231: error: previous  
implicit declaration of ‘hypercall_tx’ was here
/home/kvm/kvm-userspace/drivers/hypercall.c: In function  
‘hypercall_interrupt’:
/home/kvm/kvm-userspace/drivers/hypercall.c:302: warning: passing  
argument 1 of ‘__constant_memcpy’ makes pointer from integer without  
a cast
/home/kvm/kvm-userspace/drivers/hypercall.c:302: warning: passing  
argument 1 of ‘__memcpy’ makes pointer from integer without a cast
/home/kvm/kvm-userspace/drivers/hypercall.c: In function  
‘hypercall_open’:
/home/kvm/kvm-userspace/drivers/hypercall.c:320: warning: passing  
argument 2 of ‘request_irq’ from incompatible pointer type
/home/kvm/kvm-userspace/drivers/hypercall.c:326: warning: assignment  
makes integer from pointer without a cast
/home/kvm/kvm-userspace/drivers/hypercall.c:328: error:  
‘hypercall_task’ undeclared (first use in this function)
/home/kvm/kvm-userspace/drivers/hypercall.c:328: error: (Each  
undeclared identifier is reported only once
/home/kvm/kvm-userspace/drivers/hypercall.c:328: error: for each  
function it appears in.)
make[2]: *** [/home/kvm/kvm-userspace/drivers/hypercall.o] Error 1
make[1]: *** [_module_/home/kvm/kvm-userspace/drivers] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-2.6.20-16-generic'
make: *** [all] Error 2

Thanks,
Cam

-----------------------------------------------
A. Cameron Macdonell
Ph.D. Student
Department of Computing Science
University of Alberta
cam-edFDblaTWIyXbbII50Afww@public.gmane.org




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Re: Using VMChannel to communicate with the host.

[Dor Laor]

Cameron Macdonell wrote:
>
> On 15-Sep-07, at 4:47 PM, Dor Laor wrote:
>
> > Cam Macdonell wrote:
> >> It didn't work.  I used the following option: -vmchannel
> >> di:2258,tcp:0:4444,server (the // confused kvm) and when the VM 
> >> booted,
> >> I connected with "telnet localhost 4444" which allowed the boot to
> >> proceed.  But, I didn't get the hello host message when I loaded the
> >> hypercall module.  dmesg did show that the module loaded 
> >> successfully.
> >> I'll dig around with it and see what else I can figure ou
> >>
> > I just tried it and it worked. I used fc7 2.6.21 kernel, 64 bits  
> > for the guest.
> > Can you send the relevant dmesg?
>
> Here is the dmesg output within the guest.  I am running KVM-39 on 
> Ubuntu 2.6.20 kernel, 32 bit for both
> host and guest.
>
> [  540.144000] Qumranet_hypercall_driver
> [  540.148000] pci dev 0000:00:04.0 (id 5002:2258 rev 00) is a guest 
> hypercall device
> [  540.148000] PCI: Found IRQ 9 for device 0000:00:04.0
> [  540.148000] hypercall_init_board: PIO region size == 0x100
> [  540.148000] hypercall_init_board: MMIO region size == 0x00
> [  540.148000] name=: base_addr=0xc200, io_addr=0x1c200, IRQ=9
>
Well this part looks good, I'll try to run 32 bit guest later on.
>
> For what it's worth, I can compile the driver/hypercall.c file that 
> comes with kvm-39.  However, I can't compile your hypercall.c 
> implementation, I get the following error:
>
Hmm, well it's an old code that Uri will rebase for virtio so just drop it.
I just thought it might help.
>
> make -C /lib/modules/2.6.20-16-generic/build M=`pwd` "$@"
> make[1]: Entering directory `/usr/src/linux-headers-2.6.20-16-generic'
>    CC [M]  /home/kvm/kvm-userspace/drivers/hypercall.o
> /home/kvm/kvm-userspace/drivers/hypercall.c: In function 
> ‘hypercall_do_tasklet’:
> /home/kvm/kvm-userspace/drivers/hypercall.c:226: error: invalid 
> lvalue in unary ‘&’
> /home/kvm/kvm-userspace/drivers/hypercall.c:226: error: invalid 
> lvalue in unary ‘&’
> /home/kvm/kvm-userspace/drivers/hypercall.c:231: warning: implicit 
> declaration of function ‘hypercall_tx’
> /home/kvm/kvm-userspace/drivers/hypercall.c: At top level:
> /home/kvm/kvm-userspace/drivers/hypercall.c:236: error: static 
> declaration of ‘hypercall_tx’ follows non-static declaration
> /home/kvm/kvm-userspace/drivers/hypercall.c:231: error: previous 
> implicit declaration of ‘hypercall_tx’ was here
> /home/kvm/kvm-userspace/drivers/hypercall.c: In function 
> ‘hypercall_interrupt’:
> /home/kvm/kvm-userspace/drivers/hypercall.c:302: warning: passing 
> argument 1 of ‘__constant_memcpy’ makes pointer from integer without 
> a cast
> /home/kvm/kvm-userspace/drivers/hypercall.c:302: warning: passing 
> argument 1 of ‘__memcpy’ makes pointer from integer without a cast
> /home/kvm/kvm-userspace/drivers/hypercall.c: In function 
> ‘hypercall_open’:
> /home/kvm/kvm-userspace/drivers/hypercall.c:320: warning: passing 
> argument 2 of ‘request_irq’ from incompatible pointer type
> /home/kvm/kvm-userspace/drivers/hypercall.c:326: warning: assignment 
> makes integer from pointer without a cast
> /home/kvm/kvm-userspace/drivers/hypercall.c:328: error: 
> ‘hypercall_task’ undeclared (first use in this function)
> /home/kvm/kvm-userspace/drivers/hypercall.c:328: error: (Each 
> undeclared identifier is reported only once
> /home/kvm/kvm-userspace/drivers/hypercall.c:328: error: for each 
> function it appears in.)
> make[2]: *** [/home/kvm/kvm-userspace/drivers/hypercall.o] Error 1
> make[1]: *** [_module_/home/kvm/kvm-userspace/drivers] Error 2
> make[1]: Leaving directory `/usr/src/linux-headers-2.6.20-16-generic'
> make: *** [all] Error 2
>
> Thanks,
> Cam
>
> -----------------------------------------------
> A. Cameron Macdonell
> Ph.D. Student
> Department of Computing Science
> University of Alberta
> cam-edFDblaTWIyXbbII50Afww@public.gmane.org
>
>
>


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Re: Using VMChannel to communicate with the host.

[Cam Macdonell]

Dor Laor wrote:

>>
> Hmm, well it's an old code that Uri will rebase for virtio so just drop it.
> I just thought it might help.
>>

No worries.  In terms of moving to virtIO I grabbed your tree previously 
to look at it.  To test and play around with virtIO, do I need to use 
your kernel (or module) in the guest?

Thanks,
Cam

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Re: Using VMChannel to communicate with the host.

[Dor Laor]

Cam Macdonell wrote:
> Dor Laor wrote:
>
>>>
>> Hmm, well it's an old code that Uri will rebase for virtio so just 
>> drop it.
>> I just thought it might help.
>>>
>
> No worries.  In terms of moving to virtIO I grabbed your tree 
> previously to look at it.  To test and play around with virtIO, do I 
> need to use your kernel (or module) in the guest?
>
You can use any kernel, just load the kvm-pv, virtio-net, virtio-be, 
kvm-net modules in the guest in this order.
Pull again since I fixed some bugs yesterday.

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