Re: [Qemu-devel] [PATCH v2 0/2] Enforce gaps between DIMMs

[Michael S. Tsirkin]

On Mon, Oct 26, 2015 at 01:30:36PM +0530, Bharata B Rao wrote:
> The suggested way to work around the virtio bug reported here
> 
> http://lists.nongnu.org/archive/html/qemu-devel/2015-08/msg00522.html
> 
> is to introduce gaps between DIMMs. Igor's patchset changes the pc-dimm
> auto-address assignment to introduce gaps and ues the same from pc memhp.
> This patchset does the same for sPAPR PowerPC.
> 
> Before introducing the gap, ensure that memory hotplug region has enough
> room for alignment adjustment. We accommodate a max alignment of 256MB for
> each slot since sPAPR memory hotplug enforces an alignment requirement of
> 256MB on RAM size, maxmem and NUMA node mem sizes.
> 
> This applies on David's spapr-next branch.

This is already creating problems on x86.


Instead of propagating this all over the place,
let's fix things properly to either

- handle requests that cross the DIMMs
or
- make sure guest physically contigious implies host virtually
  contigious

> Changes in v2
> -------------
> - Minor rewording of patch description and code comment in 1/2.
> 
> v1: http://lists.nongnu.org/archive/html/qemu-devel/2015-10/msg02414.html
> v0: https://lists.gnu.org/archive/html/qemu-devel/2015-10/msg00749.html
> 
> Bharata B Rao (2):
>   spapr: Accommadate alignment gaps in hotplug memory region
>   spapr: Force gaps between DIMM's GPA
> 
>  hw/ppc/spapr.c | 23 ++++++++++++++++++-----
>  1 file changed, 18 insertions(+), 5 deletions(-)
> 
> -- 
> 2.1.0