Re: [Qemu-devel] [PATCH] qemu_vmalloc: align properly for transparent hugepages and KVM

[Avi Kivity <avi@redhat.com>]

On 09/05/2011 01:10 PM, Jan Kiszka wrote:
> On 2011-09-05 10:07, Avi Kivity wrote:
> >  To make good use of transparent hugepages, KVM requires that guest-physical
> >  and host-virtual addresses share the low 21 bits (as opposed to just the low
> >  12 bits normally required).
> >
> >  Adjust qemu_vmalloc() to honor that requirement.  Ignore it for small regions
> >  to avoid fragmentation.
> >
> >  Signed-off-by: Avi Kivity<avi@redhat.com>
> >  ---
> >   oslib-posix.c |   14 +++++++++++++-
> >   1 files changed, 13 insertions(+), 1 deletions(-)
> >
> >  diff --git a/oslib-posix.c b/oslib-posix.c
> >  index 196099c..a304fb0 100644
> >  --- a/oslib-posix.c
> >  +++ b/oslib-posix.c
> >  @@ -35,6 +35,13 @@
> >   extern int daemon(int, int);
> >   #endif
> >
> >  +#if defined(__linux__)&&  defined(__x86_64__)
> >  +   /* Use 2MB alignment so transparent hugepages can be used by KVM */
>
> Aren't transparent hugepages also available in TCG mode? Then just
> remove "by KVM" from subject and comment.

They are, but they don't require the special alignment.

-- 
error compiling committee.c: too many arguments to function