Виртуализация ввода/вывода

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 * Yes, real IOMMUs (at least Intel's VT-d) are available on the                                                                             
market today, both as loose motherboards and in OEM systems.  For                                                                            
details see /docs/misc/vtd.txt in the Xen source.  To repeat what is                                                                         
in that file:                                                                                                                                
  1) For VT-d enabling work on Xen, we have been using development                                                                           
  systems using following Intel motherboards:                                                                                                
      - DQ35MP                                                                                                                               
      - DQ35JO                                                                                                                               
  2) As far as we know, following OEM systems also has vt-d enabled.                                                                         
  Feel free to add others as they become available.                                                                                          
    - HP Compaq:  DC7800                                                                                                                     
This is very recent...I think the motherboards only became generally                                                                         
available this spring.  Anyway I ordered a Dell Optiplex 755 and it                                                                          
does indeed have VT-d and it works with Xen.                                                                                                 
  * I'm not sure about AMD's IOMMU...my impression is that it is                                                                             
currently not generally available, and/or there is less support in                                                                           
  * If your motherboard/chipset supports VT-d, you will see it in the                                                                        
BIOS configuration (it will probably be turned off by default).                                                                              
Again, unless you motherboard is very new or acquired in a                                                                                   
non-standard way, it will _not_ have VT-d.                                                                                                   
  * Support in Xen was introduced by Intel in 3.2, which is just now                                                                         
getting ready to release.  On 3.2 (unstable) I've been able to get a                                                                         
PCI NIC to pass through, but not a PCI Express graphics card (that                                                                           
story is on another thread).  There _does_ seem to be testing of a PCI                                                                       
Express NIC so I guess PCI Express is in general supported.                                                                                  
  * You are correct that open-source PV drivers for Windows DomUs are                                                                        
just now under development and of course are being developed on a                                                                            
per-device type basis.  IOMMU allows you to pass through an arbitrary                                                                        
PCI device so you need neither PV drivers nor qemu emulation.  This                                                                          
will presumaby perform well as you suggest, and more importantly it                                                                          
allows you to use device types that qemu doesn't emulate!    

HP DL380-G5's are available, as are Dell 2950's. I've used both                                                                              
successfully, just make sure to get the right CPU's. I've worked direcly                                                                     
only with Intel, not AMD with this kind of virtualization.                                                                                   
Note that nieither of them enable this by *default*, you have to configure                                                                   
it in the BIOS. This means that BIOS upgrades or 3 failed reboots in a row                                                                   
will revert the system to VT disabled, and you'll need console access to                                                                     
re-enable it, until and unless you have something like a LinuxBIOS                                                                           

I assume here you are talking about VT and not VT-d, right? I don't know about Dell 2950 machines, but HP DL380-G5 servers don't support     
+VT-d, but only VT! That's a difference... 

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