Re: [libvirt] [PATCH RFC] Add domainSave/Restore to libxl driver

This patch adds save/restore functionality to the libxl driver. It is a v2 of this patch: https://www.redhat.com/archives/libvir-list/2011-April/msg00338.html v2: * header is now padded and has a version field * the correct restore function from libxl is used * only create the restore event once in libxlVmStart

However I ran into a reproducible segfault. Assume you saved a vm with: # virsh save domU foo.img

If you restore the save image, destroy the vm and restore it again, a segfault occurs: # virsh restore foo.img # virsh destroy domU # virsh restore foo.img # segfault If you restart libvirt between the restores no segfault occurs: # virsh restore foo.img # virsh destroy domU # restart libvirt # virsh restore foo.img According to a gdb backtrace a memcpy from the function xc_domain_restore is causing the segfault. Then I saved a vm with the xl tool (which also uses the libxenlight interface) and restored it twice. No segfault occured. So I figured something must went wrong in libvirt. However I was unable to identify the responsible part of code. Now I am hoping that a review will possibly solve this issue. Here is the gdb backtrace: Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x42ba1950 (LWP 23813)] 0x00007f1bc17d906b in memcpy () from /lib/libc.so.6 (gdb) bt #0 0x00007f1bc17d906b in memcpy () from /lib/libc.so.6 #1 0x00007f1bc2b49346 in xc_domain_restore () from /usr/lib/libxenguest.so.4.0 #2 0x00007f1bc31a80f3 in ?? () from /usr/lib/libxenlight.so.1.0 #3 0x00007f1bc31a105e in ?? () from /usr/lib/libxenlight.so.1.0 #4 0x000000000049389a in libxlVmStart (driver=0x7f1bb8003e80, vm=0x7f1bb8053400, start_paused=false, restore_fd=20) at libxl/libxl_driver.c:531 #5 0x00000000004945c5 in libxlDomainRestore (conn=<value optimized out>, from=<value optimized out>) at libxl/libxl_driver.c:1745 #6 0x00007f1bc1f85a4b in virDomainRestore (conn=0x20a4d40, from=0x7f1bb804d260 "/root/tt.img") at libvirt.c:2330 #7 0x000000000042c5b8 in remoteDispatchDomainRestore (server=<value optimized out>, client=<value optimized out>, conn=0xaf0, hdr=<value optimized out>, rerr=0x42ba0e20, args=0xffffffff, ret=0x42ba0f00) at remote.c:2616 #8 0x0000000000431cb7 in remoteDispatchClientRequest (server=0x209fe90, client=0x20a4ad0, msg=0x20b1aa0) at dispatch.c:524 #9 0x000000000041dd53 in qemudWorker (data=0x20a8018) at libvirtd.c:1622 #10 0x00007f1bc1cb9fc7 in start_thread () from /lib/libpthread.so.0 #11 0x00007f1bc182b64d in clone () from /lib/libc.so.6 #12 0x0000000000000000 in ?? () Cheers, Markus --- src/libxl/libxl_conf.h | 14 +++ src/libxl/libxl_driver.c | 228 ++++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 225 insertions(+), 17 deletions(-) diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h index 8c87786..e7dd3a1 100644 --- a/src/libxl/libxl_conf.h +++ b/src/libxl/libxl_conf.h @@ -1,5 +1,6 @@ /*---------------------------------------------------------------------------*/ /* Copyright (c) 2011 SUSE LINUX Products GmbH, Nuernberg, Germany. + * Copyright (C) 2011 Univention GmbH. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -17,6 +18,7 @@ * * Authors: * Jim Fehlig <jfehlig(a)novell.com&gt; + * Markus Groß <gross(a)univention.de&gt; */ /*---------------------------------------------------------------------------*/ @@ -85,6 +87,18 @@ struct _libxlDomainObjPrivate { int eventHdl; }; +#define LIBXL_SAVE_MAGIC "libvirt-xml\n \0 \r" +#define LIBXL_SAVE_VERSION 1 + +typedef struct _libxlSavefileHeader libxlSavefileHeader; +typedef libxlSavefileHeader *libxlSavefileHeaderPtr; +struct _libxlSavefileHeader { + char magic[sizeof(LIBXL_SAVE_MAGIC)-1]; + uint32_t version; + uint32_t xmlLen; + /* 24 bytes used, pad up to 64 bytes */ + uint32_t unused[10]; +}; # define libxlError(code, ...) \ virReportErrorHelper(VIR_FROM_LIBXL, code, __FILE__, \ diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c index 247d78e..56a62c9 100644 --- a/src/libxl/libxl_driver.c +++ b/src/libxl/libxl_driver.c @@ -29,6 +29,7 @@ #include <sys/utsname.h> #include <math.h> #include <libxl.h> +#include <fcntl.h> #include "internal.h" #include "logging.h" @@ -60,11 +61,10 @@ static libxlDriverPrivatePtr libxl_driver = NULL; - /* Function declarations */ static int -libxlVmStart(libxlDriverPrivatePtr driver, - virDomainObjPtr vm, bool start_paused); +libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm, + bool start_paused, int restore_fd); /* Function definitions */ @@ -188,7 +188,7 @@ libxlAutostartDomain(void *payload, const void *name ATTRIBUTE_UNUSED, virResetLastError(); if (vm->autostart && !virDomainObjIsActive(vm) && - libxlVmStart(driver, vm, false) < 0) { + libxlVmStart(driver, vm, false, -1) < 0) { err = virGetLastError(); VIR_ERROR(_("Failed to autostart VM '%s': %s"), vm->def->name, @@ -378,7 +378,7 @@ static void libxlEventHandler(int watch, break; case SHUTDOWN_reboot: libxlVmReap(driver, vm, 0); - libxlVmStart(driver, vm, 0); + libxlVmStart(driver, vm, 0, -1); break; default: VIR_INFO("Unhandled shutdown_reason %d", info.shutdown_reason); @@ -504,8 +504,8 @@ cleanup: * virDomainObjPtr should be locked on invocation */ static int -libxlVmStart(libxlDriverPrivatePtr driver, - virDomainObjPtr vm, bool start_paused) +libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm, + bool start_paused, int restore_fd) { libxl_domain_config d_config; virDomainDefPtr def = vm->def; @@ -524,12 +524,23 @@ libxlVmStart(libxlDriverPrivatePtr driver, //TODO: Balloon dom0 ?? //ret = freemem(&d_config->b_info, &d_config->dm_info); - ret = libxl_domain_create_new(&priv->ctx, &d_config, - NULL, &child_console_pid, &domid); + if (restore_fd < 0) + ret = libxl_domain_create_new(&priv->ctx, &d_config, + NULL, &child_console_pid, &domid); + else + ret = libxl_domain_create_restore(&priv->ctx, &d_config, NULL, + &child_console_pid, &domid, + restore_fd); + if (ret) { - libxlError(VIR_ERR_INTERNAL_ERROR, - _("libxenlight failed to create new domain '%s'"), - d_config.c_info.name); + if (restore_fd < 0) + libxlError(VIR_ERR_INTERNAL_ERROR, + _("libxenlight failed to create new domain '%s'"), + d_config.c_info.name); + else + libxlError(VIR_ERR_INTERNAL_ERROR, + _("libxenlight failed to restore domain '%s'"), + d_config.c_info.name); goto error; } @@ -562,7 +573,9 @@ libxlVmStart(libxlDriverPrivatePtr driver, goto error; event = virDomainEventNewFromObj(vm, VIR_DOMAIN_EVENT_STARTED, - VIR_DOMAIN_EVENT_STARTED_BOOTED); + restore_fd < 0 ? + VIR_DOMAIN_EVENT_STARTED_BOOTED : + VIR_DOMAIN_EVENT_STARTED_RESTORED); libxlDomainEventQueue(driver, event); libxl_domain_config_destroy(&d_config); @@ -1046,7 +1059,8 @@ libxlDomainCreateXML(virConnectPtr conn, const char *xml, goto cleanup; def = NULL; - if (libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0) < 0) { + if (libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0, + -1) < 0) { virDomainRemoveInactive(&driver->domains, vm); vm = NULL; goto cleanup; @@ -1566,6 +1580,186 @@ libxlDomainGetInfo(virDomainPtr dom, virDomainInfoPtr info) } static int +libxlDomainSave(virDomainPtr dom, const char * to) +{ + libxlDriverPrivatePtr driver = dom->conn->privateData; + virDomainObjPtr vm; + libxlDomainObjPrivatePtr priv; + virDomainEventPtr event = NULL; + libxlSavefileHeader hdr; + libxl_domain_suspend_info s_info; + char *xml; + uint32_t xml_len; + int fd; + int ret = -1; + + libxlDriverLock(driver); + vm = virDomainFindByUUID(&driver->domains, dom->uuid); + + if (!vm) { + char uuidstr[VIR_UUID_STRING_BUFLEN]; + virUUIDFormat(dom->uuid, uuidstr); + libxlError(VIR_ERR_NO_DOMAIN, + _("No domain with matching uuid '%s'"), uuidstr); + goto cleanup; + } + + if (!virDomainObjIsActive(vm)) { + libxlError(VIR_ERR_OPERATION_INVALID, "%s", _("Domain is not running")); + goto cleanup; + } + + priv = vm->privateData; + + if (vm->state != VIR_DOMAIN_PAUSED) { + memset(&s_info, 0, sizeof(s_info)); + + if ((fd = virFileOpenAs(to, O_CREAT|O_TRUNC|O_WRONLY, S_IRUSR|S_IWUSR, + getuid(), getgid(), 0)) < 0) { + virReportSystemError(-fd, + _("Failed to create domain save file '%s'"), + to); + goto cleanup; + } + + if ((xml = virDomainDefFormat(vm->def, 0)) == NULL) + goto cleanup; + xml_len = strlen(xml) + 1; + + memset(&hdr, 0, sizeof(hdr)); + memcpy(hdr.magic, LIBXL_SAVE_MAGIC, sizeof(hdr.magic)); + hdr.version = LIBXL_SAVE_VERSION; + hdr.xmlLen = xml_len; + + if (safewrite(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) { + libxlError(VIR_ERR_OPERATION_FAILED, + _("Failed to write save file header")); + goto cleanup; + } + + if (safewrite(fd, xml, xml_len) != xml_len) { + libxlError(VIR_ERR_OPERATION_FAILED, + _("Failed to write xml description")); + goto cleanup; + } + + if (libxl_domain_suspend(&priv->ctx, &s_info, dom->id, fd) != 0) { + libxlError(VIR_ERR_INTERNAL_ERROR, + _("Failed to save domain '%d' with libxenlight"), + dom->id); + goto cleanup; + } + + event = virDomainEventNewFromObj(vm, VIR_DOMAIN_EVENT_STOPPED, + VIR_DOMAIN_EVENT_STOPPED_SAVED); + + if (libxlVmReap(driver, vm, 1) != 0) { + libxlError(VIR_ERR_INTERNAL_ERROR, + _("Failed to destroy domain '%d'"), dom->id); + goto cleanup; + } + + if (!vm->persistent) { + virDomainRemoveInactive(&driver->domains, vm); + vm = NULL; + } + ret = 0; + } +cleanup: + VIR_FREE(xml); + if (VIR_CLOSE(fd) < 0) + virReportSystemError(errno, "%s", _("cannot close file")); + if (vm) + virDomainObjUnlock(vm); + if (event) + libxlDomainEventQueue(driver, event); + libxlDriverUnlock(driver); + return ret; +} + +static int +libxlDomainRestore(virConnectPtr conn, const char * from) +{ + libxlDriverPrivatePtr driver = conn->privateData; + virDomainDefPtr def = NULL; + virDomainObjPtr vm = NULL; + libxlSavefileHeader hdr; + char *xml = NULL; + int fd; + int ret = -1; + + libxlDriverLock(driver); + + if ((fd = virFileOpenAs(from, O_RDONLY, 0, getuid(), getgid(), 0)) < 0) { + libxlError(VIR_ERR_OPERATION_FAILED, + "%s", _("cannot read domain image")); + goto cleanup; + } + + if (saferead(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) { + libxlError(VIR_ERR_OPERATION_FAILED, + "%s", _("failed to read libxl header")); + goto cleanup; + } + + if (memcmp(hdr.magic, LIBXL_SAVE_MAGIC, sizeof(hdr.magic))) { + libxlError(VIR_ERR_INVALID_ARG, "%s", _("image magic is incorrect")); + goto cleanup; + } + + if (hdr.version > LIBXL_SAVE_VERSION) { + libxlError(VIR_ERR_OPERATION_FAILED, + _("image version is not supported (%d > %d)"), + hdr.version, LIBXL_SAVE_VERSION); + goto cleanup; + } + + if (hdr.xmlLen <= 0) { + libxlError(VIR_ERR_OPERATION_FAILED, + _("invalid XML length: %d"), hdr.xmlLen); + goto cleanup; + } + + if (VIR_ALLOC_N(xml, hdr.xmlLen) < 0) { + virReportOOMError(); + goto cleanup; + } + + if (saferead(fd, xml, hdr.xmlLen) != hdr.xmlLen) { + libxlError(VIR_ERR_OPERATION_FAILED, "%s", _("failed to read XML")); + goto cleanup; + } + + if (!(def = virDomainDefParseString(driver->caps, xml, + VIR_DOMAIN_XML_INACTIVE))) + goto cleanup; + + if (virDomainObjIsDuplicate(&driver->domains, def, 1) < 0) + goto cleanup; + + if (!(vm = virDomainAssignDef(driver->caps, &driver->domains, def, true))) + goto cleanup; + + def = NULL; + + if ((ret = libxlVmStart(driver, vm, false, fd)) < 0 && + !vm->persistent) { + virDomainRemoveInactive(&driver->domains, vm); + vm = NULL; + } + +cleanup: + VIR_FREE(xml); + virDomainDefFree(def); + if (VIR_CLOSE(fd) < 0) + virReportSystemError(errno, "%s", _("cannot close file")); + if (vm) + virDomainObjUnlock(vm); + libxlDriverUnlock(driver); + return ret; +} + +static int libxlDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus, unsigned int flags) { @@ -2036,7 +2230,7 @@ libxlDomainCreateWithFlags(virDomainPtr dom, goto cleanup; } - ret = libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0); + ret = libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0, -1); cleanup: if (vm) @@ -2672,8 +2866,8 @@ static virDriver libxlDriver = { NULL, /* domainSetBlkioParameters */ NULL, /* domainGetBlkioParameters */ libxlDomainGetInfo, /* domainGetInfo */ - NULL, /* domainSave */ - NULL, /* domainRestore */ + libxlDomainSave, /* domainSave */ + libxlDomainRestore, /* domainRestore */ NULL, /* domainCoreDump */ libxlDomainSetVcpus, /* domainSetVcpus */ libxlDomainSetVcpusFlags, /* domainSetVcpusFlags */ -- 1.7.1 -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list