honour maxmem from config

Commit Message

James Dingwall Aug. 15, 2017, 9:13 a.m. UTC

On Tue, Aug 15, 2017 at 05:36:52AM +0100, James Dingwall wrote:
> Hi,
> 
> From xl.cfg(5):
> 
> maxmem=MBYTES
>            Specifies the maximum amount of memory a guest can ever see.  The value of maxmem= must be equal or greater than memory=.
> 
>            In combination with memory= it will start the guest "pre-ballooned", if the values of memory= and maxmem= differ.
> 
> At present when creating (pv) domains with a configuration such as:
> 
> memory = 512
> maxmem = 1024
> 
> The maximum memory of the guest will not go above 512 (this also shows in the maxmem column in xl top).  I expect that the vm will start with 512 and then be 
> able to increase up to 1024 if there is memory available for xen to allocate and the guest is under memory pressure.  I have been carrying variations of this 
> patch originally written by Wei Liu through 4.[345] and having just jumped to 4.8 noted it is still a problem so thought I would raise this again.  With this 
> applied everything is stable and working as expected - Xen 4.8.1 + Linux 4.1.43 (dom0 and guest) with tmem enabled in Xen, dom0 and guest.
> 
> https://lists.xenproject.org/archives/html/xen-devel/2013-10/msg02228.html
> 

It looks like the patch was scrubbed from the message, here it is inline.

Thanks,
James

Patch

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index d519c8d440..0b6d81e53a 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -416,7 +416,7 @@  int libxl__build_pre(libxl__gc *gc, uint32_t domid,
         return ERROR_FAIL;
     }
 
-    if (xc_domain_setmaxmem(ctx->xch, domid, info->target_memkb + size) < 0) {
+    if (xc_domain_setmaxmem(ctx->xch, domid, info->max_memkb + size) < 0) {
         LOGE(ERROR, "Couldn't set max memory");
         return ERROR_FAIL;
     }