The libxl driver reports different values of maximum memory depending on state of a domain. If inactive, maximum memory value is reported correctly. When active, maximum memory is derived from max_pages value returned by the XEN_SYSCTL_getdomaininfolist sysctl operation. But max_pages can be changed by toolstacks and does not necessarily represent the maximum memory a domain can use during its active lifetime. A better location for determining a domain's maximum memory is the /local/domain/<id>/memory/static-max node in xenstore. This value is set from the libxl_domain_build_info.max_memkb field when creating the domain. Currently it cannot be changed nor can its value be exceeded by a balloon operation. From libvirt's perspective, always reporting maximum memory with virDomainDefGetMemoryTotal() will produce the same results as reading the static-max node in xenstore. Signed-off-by: Jim Fehlig <jfehlig(a)suse.com&gt; --- src/libxl/libxl_driver.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c index 38ad91e..040b986 100644 --- a/src/libxl/libxl_driver.c +++ b/src/libxl/libxl_driver.c @@ -1640,10 +1640,10 @@ libxlDomainGetInfo(virDomainPtr dom, virDomainInfoPtr info) if (virDomainGetInfoEnsureACL(dom->conn, vm->def) < 0) goto cleanup; + info->maxMem = virDomainDefGetMemoryTotal(vm->def); if (!virDomainObjIsActive(vm)) { info->cpuTime = 0; info->memory = vm->def->mem.cur_balloon; - info->maxMem = virDomainDefGetMemoryTotal(vm->def); } else { libxl_dominfo_init(&d_info); @@ -1655,7 +1655,6 @@ libxlDomainGetInfo(virDomainPtr dom, virDomainInfoPtr info) } info->cpuTime = d_info.cpu_time; info->memory = d_info.current_memkb; - info->maxMem = d_info.max_memkb; libxl_dominfo_dispose(&d_info); } @@ -5174,7 +5173,7 @@ libxlDomainMemoryStats(virDomainPtr dom, goto endjob; } mem = d_info.current_memkb; - maxmem = d_info.max_memkb; + maxmem = virDomainDefGetMemoryTotal(vm->def); LIBXL_SET_MEMSTAT(VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON, mem); LIBXL_SET_MEMSTAT(VIR_DOMAIN_MEMORY_STAT_AVAILABLE, maxmem); -- 2.9.2

When the libxl driver is initialized, it creates a virDomainDef object for dom0 and adds it to the list of domains. Total memory for dom0 was being set from the max_memkb field of libxl_dominfo struct retrieved from libxl, but this field can be set to LIBXL_MEMKB_DEFAULT (~0ULL) if dom0 maximum memory has not been explicitly set by the user. This patch adds some simple parsing of the Xen commandline, looking for a dom0_mem parameter that also specifies a 'max' value. If not specified, dom0 maximum memory is effectively all physical host memory. Signed-off-by: Jim Fehlig <jfehlig(a)suse.com&gt; --- V2: Check return value of libxl_get_physinfo and libxlDriverGetDom0MaxmemConf. src/libxl/libxl_conf.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++ src/libxl/libxl_conf.h | 4 +++ src/libxl/libxl_driver.c | 5 +++- 3 files changed, 85 insertions(+), 1 deletion(-) diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c index 28b05e1..7e30c7d 100644 --- a/src/libxl/libxl_conf.c +++ b/src/libxl/libxl_conf.c @@ -34,6 +34,7 @@ #include "internal.h" #include "virlog.h" #include "virerror.h" +#include "c-ctype.h" #include "datatypes.h" #include "virconf.h" #include "virfile.h" @@ -1533,6 +1534,82 @@ int libxlDriverConfigLoadFile(libxlDriverConfigPtr cfg, } +/* + * dom0's maximum memory can be controled by the user with the 'dom0_mem' Xen + * command line parameter. E.g. to set dom0's initial memory to 4G and max + * memory to 8G: dom0_mem=4G,max:8G + * + * If not constrained by the user, dom0 can effectively use all host memory. + * This function returns the configured maximum memory for dom0 in kilobytes, + * either the user-specified value or total physical memory as a default. + */ +int +libxlDriverGetDom0MaxmemConf(libxlDriverConfigPtr cfg, + unsigned long long *maxmem) +{ + char **cmd_tokens = NULL; + char **mem_tokens = NULL; + size_t i; + size_t j; + libxl_physinfo physinfo; + int ret = -1; + + if (cfg->verInfo->commandline == NULL || + !(cmd_tokens = virStringSplit(cfg->verInfo->commandline, " ", 0))) + goto physmem; + + for (i = 0; cmd_tokens[i] != NULL; i++) { + if (!STRPREFIX(cmd_tokens[i], "dom0_mem=")) + continue; + + if (!(mem_tokens = virStringSplit(cmd_tokens[i], ",", 0))) + break; + for (j = 0; mem_tokens[j] != NULL; j++) { + if (STRPREFIX(mem_tokens[j], "max:")) { + char *p = mem_tokens[j] + 4; + unsigned long long multiplier = 1; + + while (c_isdigit(*p)) + p++; + if (virStrToLong_ull(mem_tokens[j] + 4, &p, 10, maxmem) < 0) + break; + if (*p) { + switch (*p) { + case 'm': + case 'M': + multiplier = 1024; + break; + case 'g': + case 'G': + multiplier = 1024 * 1024; + break; + } + } + *maxmem = *maxmem * multiplier; + ret = 0; + goto cleanup; + } + } + } + + physmem: + /* No 'max' specified in dom0_mem, so dom0 can use all physical memory */ + libxl_physinfo_init(&physinfo); + if (libxl_get_physinfo(cfg->ctx, &physinfo)) { + VIR_WARN("libxl_get_physinfo failed"); + goto cleanup; + } + *maxmem = (physinfo.total_pages * cfg->verInfo->pagesize) / 1024; + libxl_physinfo_dispose(&physinfo); + ret = 0; + + cleanup: + virStringListFree(cmd_tokens); + virStringListFree(mem_tokens); + return ret; +} + + #ifdef LIBXL_HAVE_DEVICE_CHANNEL static int libxlPrepareChannel(virDomainChrDefPtr channel, diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h index 69d7885..4942171 100644 --- a/src/libxl/libxl_conf.h +++ b/src/libxl/libxl_conf.h @@ -174,6 +174,10 @@ int libxlDriverConfigLoadFile(libxlDriverConfigPtr cfg, const char *filename); int +libxlDriverGetDom0MaxmemConf(libxlDriverConfigPtr cfg, + unsigned long long *maxmem); + +int libxlMakeDisk(virDomainDiskDefPtr l_dev, libxl_device_disk *x_dev); int libxlMakeNic(virDomainDefPtr def, diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c index 040b986..1558d5b 100644 --- a/src/libxl/libxl_driver.c +++ b/src/libxl/libxl_driver.c @@ -576,6 +576,7 @@ libxlAddDom0(libxlDriverPrivatePtr driver) virDomainObjPtr vm = NULL; virDomainDefPtr oldDef = NULL; libxl_dominfo d_info; + unsigned long long maxmem; int ret = -1; libxl_dominfo_init(&d_info); @@ -615,7 +616,9 @@ libxlAddDom0(libxlDriverPrivatePtr driver) if (virDomainDefSetVcpus(vm->def, d_info.vcpu_online) < 0) goto cleanup; vm->def->mem.cur_balloon = d_info.current_memkb; - virDomainDefSetMemoryTotal(vm->def, d_info.max_memkb); + if (libxlDriverGetDom0MaxmemConf(cfg, &maxmem) < 0) + maxmem = d_info.current_memkb; + virDomainDefSetMemoryTotal(vm->def, maxmem); ret = 0; -- 2.9.2

On 02/09/2017 12:39 PM, Joao Martins wrote: To avoid ambiguity here I meant the snippet above doesn't Terabytes, but its correspondent support on Xen is only since 4.5. Joao

On 02/09/2017 04:58 PM, Jim Fehlig wrote: Looking good indeed, and with that diff I have no further comments: Acked-by: Joao Martins <joao.m.martins(a)oracle.com&gt;