[PATCH 2/4] libxl: vcpuset: Check max_vcpus argument against the maximum number of vCPUs the guest has set.

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

The maximum number of VCPUs the guest can have is determined during
domain creation and is set by 'maxvcpus' parameter (in the guest
config). Trying to set the amount of vCPUs above said value
in vcpuset will result in an error - and we can catch it here
(instead of later in the function) and print a nice warning to the user.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 tools/libxl/xl_cmdimpl.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 378ede1..d22ba85 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -5018,6 +5018,7 @@ static int vcpuset(uint32_t domid, const char* nr_vcpus, int check_host)
     char *endptr;
     unsigned int max_vcpus, i;
     libxl_bitmap cpumap;
+    libxl_dominfo dominfo;
     int rc;
 
     libxl_bitmap_init(&cpumap);
@@ -5026,7 +5027,20 @@ static int vcpuset(uint32_t domid, const char* nr_vcpus, int check_host)
         fprintf(stderr, "Error: Invalid argument.\n");
         return -ERROR_INVAL;
     }
-
+    rc = libxl_domain_info(ctx, &dominfo, domid);
+    if (rc == ERROR_INVAL) {
+        fprintf(stderr, "Error: Domain %u does not exist.\n", domid);
+        return -rc;
+    }
+    if (rc) {
+        fprintf(stderr, "libxl_domain_info failed (code %d).\n", rc);
+        return -rc;
+    }
+    if (max_vcpus > dominfo.vcpu_max_id + 1) {
+        fprintf(stderr, "You have a max of %d vCPUs and you want %d vCPUs!\n",
+                dominfo.vcpu_max_id + 1, max_vcpus);
+        return -ERROR_INVAL;
+    }
     /*
      * Maximum amount of vCPUS the guest is allowed to set is limited
      * by the host's amount of pCPUs.
-- 
1.8.4.2