Bug#503821: Purpose of features/all/xen/workaround-pte-file.patch?
On Wed, 2008-11-05 at 10:40 +0100, Bastian Blank wrote:
> On Wed, Nov 05, 2008 at 07:06:58AM +0000, Ian Campbell wrote:
> > This patch makes mprotect work by (very skankily) hacking out large page
> > support which is unsupported on top of Xen anyway (I think so, currently
> > anyway). I think I took out PAT as collaterol damage too. A cleaned up
> > version without the pat damage might be an acceptable fix for the
> > mprotect issue.
>
> Xen have to support large pages, they are used over and over.
Xen currently only supports 4K pages (for PV guests, HVM obviously
supports everything). There were patches to enable larger page types
recently on xen-devel but they aren't in any hypervisor we care about
for Lenny.
> > My suspicion is that one of the -xen.c or mach-xen/asm/ files has gotten
> > out of sync with a fix to its native partner since _PAGE_PSE is used for
> > PROTNONE on native too so they must get round it somehow. I'll have a
> > scrobble through and see if I can see it.
>
> Would make sense.
>
> What happens if you use "nopat" to disable the usage of PAT?
CONFIG_X86_PAT is disabled anyway so it makes no difference.
> The only way to generate huge pages from userspace is to use hugetlbfs, which is
> disabled.
Ian.
--
Ian Campbell
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Money is the root of all wealth.
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