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

[Ian Campbell <Ian.Campbell@citrix.com>]

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>

> ---
>  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 ?