From f8983a45fb8d02cca9b6f79e0e98084f1b51417c Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Tue, 9 Sep 2008 14:54:56 +0100 Subject: vtd.txt: Add caveat about assigning certain types of device. From: Yuji Shimada Signed-off-by: Keir Fraser --- docs/misc/vtd.txt | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) (limited to 'docs') diff --git a/docs/misc/vtd.txt b/docs/misc/vtd.txt index 277321ba23..bd6fd104cc 100644 --- a/docs/misc/vtd.txt +++ b/docs/misc/vtd.txt @@ -1,8 +1,9 @@ Title : How to do PCI Passthrough with VT-d Authors : Allen Kay Weidong Han + Yuji Shimada Created : October-24-2007 -Updated : August-06-2008 +Updated : September-09-2008 How to turn on VT-d in Xen -------------------------- @@ -106,3 +107,27 @@ http://h10010.www1.hp.com/wwpc/us/en/en/WF04a/12454-12454-64287-321860-3328898.h For more information, pls refer to http://wiki.xensource.com/xenwiki/VTdHowTo. + +Assigning devices to HVM domains +-------------------------------- + +Most device types such as NIC, HBA, EHCI and UHCI can be assigned to +an HVM domain. + +But some devices have design features which make them unsuitable for +assignment to an HVM domain. Examples include: + + * Device has an internal resource, such as private memory, which is + mapped to memory address space with BAR (Base Address Register). + * Driver submits command with a pointer to a buffer within internal + resource. Device decodes the pointer (address), and accesses to the + buffer. + +In an HVM domain, the BAR is virtualized, and host-BAR value and +guest-BAR value are different. The addresses of internal resource from +device's view and driver's view are different. Similarly, the +addresses of buffer within internal resource from device's view and +driver's view are different. As a result, device can't access to the +buffer specified by driver. + +Such devices assigned to HVM domain currently do not work. -- cgit v1.2.3