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Re: [Xen-devel] Creating HVM guest by libxenguest



Gary Pennington wrote:
On Thu, Oct 02, 2008 at 09:36:47AM +0100, Gihan Munasinghe wrote:
Hi

I am new to developing for XEN. I wanted to crate a HVM using xencltr.h and xenguest.h.. Following is the code I got from while browsing
done by Mark McLoughlin <markmc@xxxxxxxxxx> and did some modification.
============================================================================================
#include <stdio.h>
#include <xenctrl.h>
#include <xenguest.h>

#define MEM_MB 1024
#define IMAGE "/root/osimages/vmlinuz-2.6.24-19-xen"
#define INITRD NULL
#define CMDLINE ""
#define FEATURES NULL
#define FLAGS 0

int
main(int argc, char **argv)
{
int xc_handle, ret;
uint32_t domid;
unsigned int store_evtchn, console_evtchn;
unsigned long store_mfn, console_mfn;
xen_domain_handle_t uuid = {
  0xb2, 0x93, 0x22, 0x1f,
  0x1a, 0xaa, 0x20, 0xac,
  0xbe, 0x36, 0xc4, 0xd7,
  0x6b, 0x73, 0x92, 0x1,
};

xc_handle = xc_interface_open();
if (xc_handle == -1)
  {
    fprintf(stderr, "xc_interface_open() failed\n");
    return 1;
  }

domid = 0;

ret = xc_domain_create(xc_handle, 0, uuid, 0, &domid);
if (ret != 0)
  {
    fprintf(stderr, "xc_dom_linux_build() failed\n");
    goto fail;
  }

store_evtchn = xc_evtchn_alloc_unbound(xc_handle, domid, 0);
if (store_evtchn < 0)
  {
    fprintf(stderr, "Failed to allocate xenstore event channel\n");
    goto fail;
  }

console_evtchn = xc_evtchn_alloc_unbound(xc_handle, domid, 0);
if (console_evtchn < 0)
  {
    fprintf(stderr, "Failed to allocate console event channel\n");
    goto fail;
  }

ret = xc_domain_setmaxmem(xc_handle, domid, MEM_MB << 10);
if (ret != 0)
  {
    fprintf(stderr, "xc_domain_set_maxmem() failed\n");
    goto fail;
  }

ret = xc_domain_max_vcpus(xc_handle, domid, 1);
if (ret != 0)
  {
    fprintf(stderr, "xc_domain_max_vcpus() failed\n");
    goto fail;
  }


/*  ret = xc_linux_build(xc_handle, domid,524288,
                     IMAGE, INITRD,
                     CMDLINE, FEATURES, FLAGS,
                     store_evtchn, &store_mfn,
                     console_evtchn, &console_mfn);
*/
ret = xc_hvm_build(xc_handle, domid, MEM_MB, IMAGE); if (ret != 0)
  {
    fprintf(stderr, "xc_dom_linux_build() failed\n");
    goto fail;
  }


xc_interface_close(xc_handle);
  return 0;

fail:
if (domid)
  {
    xc_evtchn_reset(xc_handle, domid);
    xc_domain_destroy(xc_handle, domid);
  }
xc_interface_close(xc_handle);
return 1;
}
===============================================================

When running this code I get the following error output

VIRTUAL MEMORY ARRANGEMENT:
Loader:        00000000c0100000->00000000c0503000
TOTAL:         0000000000000000->0000000040000000
ENTRY ADDRESS: 00000000c0100000
Failed allocation for dom 12: 261952 extents of order 0
ERROR Internal error: Could not allocate memory for HVM guest.
(16 = Device or resource busy)
xc_dom_linux_build() failed


Looks like you don't have enough memory on your system to build a 1GB
guest domain...

It's trying to allocate 261952 4k pages (i.e. 1GB) and failing. You
could reduce MEM_MB or try running your program on a system with more
memory.
I am running this code in a machine with has 8GB of ram.. But when I look at though virt-manager it says dom0 is using 8GB. I think that may be the problem. Is there any XEn setting or code change I need to do get the ram back off dom0

Thanks
Gihan
Gary

Could someone give me some insight to this, also is there any source codes or documentation that I can find on using low level xen interface..

Thanks
Gihan




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