From b097186fd29d5bc5a26d1ae87995821ffc27b66e Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Tue, 11 May 2010 10:05:49 -0400 Subject: swiotlb-xen: SWIOTLB library for Xen PV guest with PCI passthrough. This patchset: PV guests under Xen are running in an non-contiguous memory architecture. When PCI pass-through is utilized, this necessitates an IOMMU for translating bus (DMA) to virtual and vice-versa and also providing a mechanism to have contiguous pages for device drivers operations (say DMA operations). Specifically, under Xen the Linux idea of pages is an illusion. It assumes that pages start at zero and go up to the available memory. To help with that, the Linux Xen MMU provides a lookup mechanism to translate the page frame numbers (PFN) to machine frame numbers (MFN) and vice-versa. The MFN are the "real" frame numbers. Furthermore memory is not contiguous. Xen hypervisor stitches memory for guests from different pools, which means there is no guarantee that PFN==MFN and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are allocated in descending order (high to low), meaning the guest might never get any MFN's under the 4GB mark. Signed-off-by: Konrad Rzeszutek Wilk Acked-by: Jeremy Fitzhardinge Cc: FUJITA Tomonori Cc: Albert Herranz Cc: Ian Campbell --- drivers/xen/Kconfig | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/xen/Kconfig') diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index fad3df2c1276..97199c2a64a0 100644 --- a/drivers/xen/Kconfig +++ b/drivers/xen/Kconfig @@ -62,4 +62,8 @@ config XEN_SYS_HYPERVISOR virtual environment, /sys/hypervisor will still be present, but will have no xen contents. +config SWIOTLB_XEN + def_bool y + depends on SWIOTLB + endmenu -- cgit v1.2.3-58-ga151