Re: [PATCH] xl, e820_host, PV passthrough: Fix guests crashing when memory == maxmem

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, May 24, 2013 at 02:58:24PM +0100, Ian Campbell wrote:
> On Fri, 2013-05-24 at 09:36 -0400, Konrad Rzeszutek Wilk wrote:
> > The code had an obvious bug where it would assume that the balloon
> > amount would always be _something_ and add an E820_RAM entry at the
> > end of the E820 array. The added E820_RAM would contain the balloon amount
> > plus the delta of memory that had to be subtracted b/c of the various
> > E820 entries. That assumption is certainly true when maxmem != mem,
> > but if guest config has maxmem = memory that is incorrect (as balloon
> > value is zero). The end result is that the E820 that is constructed
> > is missing a swath of "delta" memory and in most cases ends up with
> > only one E820_RAM entry that is of 512MB size on many Intel systems.
> > 
> > Reported-by: Christian Holpert <christian@holpert.de>
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>

George,
Would you be OK putting this in Xen 4.3? It is only exposed if a user
 1) launches a PV guest
 2). Has in the guest config: pci=['blabla']\ne820_host=1
 3). Is not that freq used as only a couple of people seem to use it

> 
> > ---
> >  tools/libxl/libxl_x86.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/tools/libxl/libxl_x86.c b/tools/libxl/libxl_x86.c
> > index a17f6ae..a78c91d 100644
> > --- a/tools/libxl/libxl_x86.c
> > +++ b/tools/libxl/libxl_x86.c
> > @@ -182,7 +182,7 @@ static int e820_sanitize(libxl_ctx *ctx, struct e820entry src[],
> >          idx++;
> >      }
> >      /* At this point we have the mapped RAM + E820 entries from src. */
> > -    if (balloon_kb) {
> > +    if (balloon_kb || delta_kb) {
> >          /* and if we truncated the RAM region, then add it to the end. */
> >          e820[idx].type = E820_RAM;
> >          e820[idx].addr = (uint64_t)(1ULL << 32) > last ?
> 
>