Re: [libvirt] [PATCH] libxl: add support for mounts in HVM guests

Xen HVM guests are running a QEMU, libxl allows passing QEMU parameters in the d_config.b_info.extra list. Take advantage of that to implement support for 9pfs mounts. For this to work, xen's qemu needs to be built with virtfs enabled, or an upstream qemu needs to be used.

--- Note that two functions have been picked from the qemu driver's code. src/libxl/libxl_conf.c | 174 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 174 insertions(+) diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c index 4eed5ca..4437e8f 100644 --- a/src/libxl/libxl_conf.c +++ b/src/libxl/libxl_conf.c @@ -55,6 +55,7 @@ VIR_LOG_INIT("libxl.libxl_conf"); /* see xen-unstable.hg/xen/include/asm-x86/cpufeature.h */ #define LIBXL_X86_FEATURE_PAE_MASK 0x40 +#define LIBXL_FSDEV_HOST_PREFIX "fsdev-" struct guest_arch { virArch arch; @@ -84,6 +85,15 @@ static int libxlConfigOnceInit(void) VIR_ONCE_GLOBAL_INIT(libxlConfig) +VIR_ENUM_DECL(libxlDomainFSDriver) +VIR_ENUM_IMPL(libxlDomainFSDriver, VIR_DOMAIN_FS_DRIVER_TYPE_LAST, + "local", + "local", + "handle", + NULL, + NULL, + NULL); + static void libxlDriverConfigDispose(void *obj) { @@ -1854,6 +1864,167 @@ libxlMakeCapabilities(libxl_ctx *ctx) return NULL; } +static char * +libxlBuildQemuFSStr(virDomainFSDefPtr fs) +{ + virBuffer opt = VIR_BUFFER_INITIALIZER; + const char *driver = libxlDomainFSDriverTypeToString(fs->fsdriver); + const char *wrpolicy = virDomainFSWrpolicyTypeToString(fs->wrpolicy); + + if (fs->type != VIR_DOMAIN_FS_TYPE_MOUNT) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("only supports mount filesystem type")); + goto error; + } + + if (!driver) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("Filesystem driver type not supported")); + goto error; + } + virBufferAdd(&opt, driver, -1); + + if (fs->fsdriver == VIR_DOMAIN_FS_DRIVER_TYPE_PATH || + fs->fsdriver == VIR_DOMAIN_FS_DRIVER_TYPE_DEFAULT) { + if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_MAPPED) { + virBufferAddLit(&opt, ",security_model=mapped"); + } else if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_PASSTHROUGH) { + virBufferAddLit(&opt, ",security_model=passthrough"); + } else if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_SQUASH) { + virBufferAddLit(&opt, ",security_model=none"); + } + } else { + /* For other fs drivers, default(passthru) should always + * be supported */ + if (fs->accessmode != VIR_DOMAIN_FS_ACCESSMODE_PASSTHROUGH) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("only supports passthrough accessmode")); + goto error; + } + } + + if (fs->wrpolicy) + virBufferAsprintf(&opt, ",writeout=%s", wrpolicy); + + virBufferAsprintf(&opt, ",id=%s%s", LIBXL_FSDEV_HOST_PREFIX, fs->info.alias); + virBufferAsprintf(&opt, ",path=%s", fs->src); + + if (fs->readonly) + virBufferAddLit(&opt, ",readonly"); + + if (virBufferCheckError(&opt) < 0) + goto error; + + return virBufferContentAndReset(&opt); + + error: + virBufferFreeAndReset(&opt); + return NULL; +} + + +static char * +libxlBuildQemuFSDevStr(virDomainFSDefPtr fs) +{ + virBuffer opt = VIR_BUFFER_INITIALIZER; + + if (fs->type != VIR_DOMAIN_FS_TYPE_MOUNT) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("can only passthrough directories")); + goto error; + } + + if (fs->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_CCW) + virBufferAddLit(&opt, "virtio-9p-ccw"); + else + virBufferAddLit(&opt, "virtio-9p-pci"); + + virBufferAsprintf(&opt, ",id=%s", fs->info.alias); + virBufferAsprintf(&opt, ",fsdev=%s%s", LIBXL_FSDEV_HOST_PREFIX, fs->info.alias); + virBufferAsprintf(&opt, ",mount_tag=%s", fs->dst); + + if (virBufferCheckError(&opt) < 0) + goto error; + + return virBufferContentAndReset(&opt); + + error: + virBufferFreeAndReset(&opt); + return NULL; +}

+ +static int +libxlMakeMountList(virDomainDefPtr def, + libxl_domain_config *d_config) +{ + int ret = -1; + size_t i; + size_t nextra = 0; + char *fsstr = NULL; + char *fsdevstr = NULL; + char *fsdevargstr = NULL; + char *deviceargstr = NULL; + + if (def->nfss > 0 && def->os.type != VIR_DOMAIN_OSTYPE_HVM) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("only HVM guests supports mounts")); + return ret; + } + + /* Make sure we have an allocated array, not ending with NULL */ + if (!d_config->b_info.extra) { + if (VIR_ALLOC(d_config->b_info.extra) < 0) + return ret; + nextra = 0; + } else { + nextra = virStringListLength(d_config->b_info.extra) + 1; + if (VIR_DELETE_ELEMENT(d_config->b_info.extra, nextra, nextra) < 0) + return ret; + } + + /* Add the QEMU options to d_config->b_info->extra + * -fsdev local,id=virtio9p,path=%s,security_model=none + * -device virtio-9p-pci,fsdev=virtio9p,mount_tag=%s + */ + for (i = 0; i < def->nfss; i++) { + virDomainFSDefPtr fs = def->fss[i]; + + /* Assign an alias */ + if (virAsprintf(&fs->info.alias, "fs%zu", i) < 0) + goto cleanup; + + if (!(fsstr = libxlBuildQemuFSStr(fs))) + goto cleanup; + if (!(fsdevstr = libxlBuildQemuFSDevStr(fs))) + goto cleanup; + + if (VIR_STRDUP(fsdevargstr, "-fsdev") < 0 || + VIR_STRDUP(deviceargstr, "-device") < 0) + goto cleanup; + + + /* Append to the extras before terminating NULL */ + if (VIR_APPEND_ELEMENT(d_config->b_info.extra, nextra, fsdevargstr) < 0 || + VIR_APPEND_ELEMENT(d_config->b_info.extra, nextra, fsstr) < 0 || + VIR_APPEND_ELEMENT(d_config->b_info.extra, nextra, deviceargstr) < 0 || + VIR_APPEND_ELEMENT(d_config->b_info.extra, nextra, fsdevstr) < 0) + goto cleanup; + } + ret = 0; + + /* Add the terminating NULL item */ + if (VIR_RESIZE_N(d_config->b_info.extra, nextra, nextra, 1) < 0) + goto cleanup; + d_config->b_info.extra[nextra++] = NULL; + + cleanup: + VIR_FREE(fsstr); + VIR_FREE(fsdevstr); + VIR_FREE(fsdevargstr); + VIR_FREE(deviceargstr); + return ret; +} + int libxlBuildDomainConfig(virPortAllocatorPtr graphicsports, virDomainDefPtr def, @@ -1883,6 +2054,9 @@ libxlBuildDomainConfig(virPortAllocatorPtr graphicsports, if (libxlMakePCIList(def, d_config) < 0) return -1; + if (libxlMakeMountList(def, d_config) < 0) + return -1; +