From 93e52d5242804ff928131553599afa769f85481b Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Thu, 23 Oct 2014 10:19:53 +0200 Subject: [PATCH] fix listing of vcpus when domains lacking any vcpus exist On a system which looks like this: [root@st04 ~]# xl list Name ID Mem VCPUs State Time(s) Domain-0 0 752 4 r----- 46699.3 (null) 1 0 0 --p--- 0.0 (null) 2 0 0 --p--- 0.0 (null) 3 0 0 --p--- 0.0 badger 25 0 1 --p--- 0.0 `xl vcpu-list` failes as so: [root@st04 ~]# xl vcpu-list Name ID VCPU CPU State Time(s) CPU Affinity Domain-0 0 0 0 -b- 12171.0 all Domain-0 0 1 1 -b- 11779.6 all Domain-0 0 2 2 -b- 11599.0 all Domain-0 0 3 3 r-- 11007.0 all libxl: critical: libxl__calloc: libxl: FATAL ERROR: memory allocation failure (libxl__calloc, 4294935299 x 40) : Cannot allocate memory libxl: FATAL ERROR: memory allocation failure (libxl__calloc, 4294935299 x 40) The root cause of this is in Xen. getdomaininfo() has no way of expressing "this domain has no vcpus". Previously, info->max_vcpu_id would be returned uninitialised in such a case. Unfortunately, setting it to 0 as a default is not appropriate. A max_vcpu_id of 0 and nr_online_cpus of 0 is the valid state for a single vcpu domain which is in the process of being destroyed. As all components are required to add 1 to max_vcpu_id to get the number of vcpus, an id of ~0U is not valid to be used. Explicitly define this as an invalid max vcpu value, and use it to express "no vcpus" in getdomaininfo() In libxl, the issue is seen as libxl_list_vcpu() attempts to use the uninitialised domaininfo.max_vcpu_id for memory allocation. Check domaininfo.max_vcpu_id against the new sentinel value XEN_INVALID_MAX_VCPU_ID, and return early. This means that it is now valid for libxl_list_vcpu() to return NULL for a domain which lacks any vcpus. As part of this change, remove the pointless call to libxl_get_max_cpus(), whose returned value is unconditionally clobbered in the for() loop. Reported-by: Euan Harris Signed-off-by: Andrew Cooper Acked-by: Jan Beulich Reviewed-by: Don Slutz Acked-by: Ian Campbell --- tools/libxl/libxl.c | 7 ++++++- tools/libxl/xl_cmdimpl.c | 4 +--- xen/common/domctl.c | 1 + xen/include/public/domctl.h | 1 + 4 files changed, 9 insertions(+), 4 deletions(-) diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c index f27b5813ce..ee127d8ef0 100644 --- a/tools/libxl/libxl.c +++ b/tools/libxl/libxl.c @@ -5246,7 +5246,12 @@ libxl_vcpuinfo *libxl_list_vcpu(libxl_ctx *ctx, uint32_t domid, GC_FREE; return NULL; } - *nr_cpus_out = libxl_get_max_cpus(ctx); + + if (domaininfo.max_vcpu_id == XEN_INVALID_MAX_VCPU_ID) { + GC_FREE; + return NULL; + } + ret = ptr = libxl__calloc(NOGC, domaininfo.max_vcpu_id + 1, sizeof(libxl_vcpuinfo)); diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c index ea43761101..0882644392 100644 --- a/tools/libxl/xl_cmdimpl.c +++ b/tools/libxl/xl_cmdimpl.c @@ -4813,10 +4813,8 @@ static void print_domain_vcpuinfo(uint32_t domid, uint32_t nr_cpus) vcpuinfo = libxl_list_vcpu(ctx, domid, &nb_vcpu, &nrcpus); - if (!vcpuinfo) { - fprintf(stderr, "libxl_list_vcpu failed.\n"); + if (!vcpuinfo) return; - } for (i = 0; i < nb_vcpu; i++) { print_vcpuinfo(domid, &vcpuinfo[i], nr_cpus); diff --git a/xen/common/domctl.c b/xen/common/domctl.c index b6f9708c25..d9c26350a4 100644 --- a/xen/common/domctl.c +++ b/xen/common/domctl.c @@ -156,6 +156,7 @@ void getdomaininfo(struct domain *d, struct xen_domctl_getdomaininfo *info) struct vcpu_runstate_info runstate; info->domain = d->domain_id; + info->max_vcpu_id = XEN_INVALID_MAX_VCPU_ID; info->nr_online_vcpus = 0; info->ssidref = 0; diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h index f519524fe8..58b19e7c1f 100644 --- a/xen/include/public/domctl.h +++ b/xen/include/public/domctl.h @@ -108,6 +108,7 @@ struct xen_domctl_getdomaininfo { uint64_aligned_t shared_info_frame; /* GMFN of shared_info struct */ uint64_aligned_t cpu_time; uint32_t nr_online_vcpus; /* Number of VCPUs currently online. */ +#define XEN_INVALID_MAX_VCPU_ID (~0U) /* Domain has no vcpus? */ uint32_t max_vcpu_id; /* Maximum VCPUID in use by this domain. */ uint32_t ssidref; xen_domain_handle_t handle; -- 2.30.2