[ofa-general] Re: InfiniBand card (mthca) in Linux

[Lukas Hejtmanek]

On Sun, Jul 08, 2007 at 10:03:16PM -0700, Roland Dreier wrote:
> Is the memory given to a domU always physically contiguous?  If not,
> what happens when a domU kernel does alloc_pages(GFP_KERNEL, 6) to try
> and allocate 256 KB or something like that.  Let's assume that the
> domU kernel has enough guest contiguous pages to satisfy the
> allocation -- is there any guarantee that the pages are really
> physically contiguous?

according to Xen-dev alloc_pages does *not* guarantee contiguous pages. They
say that the pci_alloc_consistent should be used instead. The question is
whether non-Xen kernel *usually* allocates contiguous pages and so far it has
been working and whether it should be fixed in the mainline of the driver.

I do some tests (and also try to figure out how to change alloc_pages to
pci_alloc_consistent) to verify contiguous pages.

Anyway, thanks a lot!!

-- 
Lukáš Hejtmánek