@@ -1262,6 +1262,11 @@ FIFO-based event channel ABI support up to 131,071 event channels.
Other guests are limited to 4095 (64-bit x86 and ARM) or 1023 (32-bit
x86).
+=item B<disable_evtchn_fifo=BOOLEAN>
+
+Indicates if support for FIFO event channel ABI is disabled. The default
+is false (0).
+
=item B<vdispl=[ "VDISPL_SPEC_STRING", "VDISPL_SPEC_STRING", ...]>
Specifies the virtual display devices to be provided to the guest.
@@ -169,6 +169,14 @@
*/
#define LIBXL_HAVE_BUILDINFO_EVENT_CHANNELS 1
+/*
+ * LIBXL_HAVE_BUILDINFO_DISABLE_EVTCHN_FIFO indicates that the
+ * libxl_domain_build_info structure contains a boolean
+ * disable_evtchn_fifo which instructs libxl to enable/disable
+ * support for FIFO event channel ABI at create time.
+ */
+#define LIBXL_HAVE_BUILDINFO_DISABLE_EVTCHN_FIFO 1
+
/*
* libxl_domain_build_info has the u.hvm.ms_vm_genid field.
*/
@@ -217,6 +217,8 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
if (!b_info->event_channels)
b_info->event_channels = 1023;
+ libxl_defbool_setdefault(&b_info->disable_evtchn_fifo, false);
+
libxl__arch_domain_build_info_setdefault(gc, b_info);
libxl_defbool_setdefault(&b_info->dm_restrict, false);
@@ -564,6 +566,9 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
libxl_defbool_val(info->oos) ? 0 : XEN_DOMCTL_CDF_oos_off;
}
+ if (libxl_defbool_val(b_info->disable_evtchn_fifo))
+ create.flags |= XEN_DOMCTL_CDF_disable_fifo;
+
/* Ultimately, handle is an array of 16 uint8_t, same as uuid */
libxl_uuid_copy(ctx, (libxl_uuid *)&create.handle, &info->uuid);
@@ -521,6 +521,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
("iomem", Array(libxl_iomem_range, "num_iomem")),
("claim_mode", libxl_defbool),
("event_channels", uint32),
+ ("disable_evtchn_fifo", libxl_defbool),
("kernel", string),
("cmdline", string),
("ramdisk", string),
@@ -1496,6 +1496,8 @@ void parse_config_data(const char *config_source,
if (!xlu_cfg_get_long(config, "max_event_channels", &l, 0))
b_info->event_channels = l;
+ xlu_cfg_get_defbool(config, "disable_evtchn_fifo",
+ &b_info->disable_evtchn_fifo, 0);
xlu_cfg_replace_string (config, "kernel", &b_info->kernel, 0);
xlu_cfg_replace_string (config, "ramdisk", &b_info->ramdisk, 0);
xlu_cfg_replace_string (config, "device_tree", &b_info->device_tree, 0);
@@ -71,6 +71,8 @@ void printf_info_sexp(int domid, libxl_domain_config *d_config, FILE *fh)
fprintf(fh, "\t(target_memkb %"PRId64")\n", b_info->target_memkb);
fprintf(fh, "\t(nomigrate %s)\n",
libxl_defbool_to_string(b_info->disable_migrate));
+ fprintf(fh, "\t(disable_evtchn_fifo %s)\n",
+ libxl_defbool_to_string(b_info->disable_evtchn_fifo));
if (c_info->type == LIBXL_DOMAIN_TYPE_PV && b_info->bootloader) {
fprintf(fh, "\t(bootloader %s)\n", b_info->bootloader);
@@ -1170,6 +1170,7 @@ long do_event_channel_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
case EVTCHNOP_init_control: {
struct evtchn_init_control init_control;
+
if ( copy_from_guest(&init_control, arg, 1) != 0 )
return -EFAULT;
rc = evtchn_fifo_init_control(&init_control);
@@ -513,6 +513,10 @@ int evtchn_fifo_init_control(struct evtchn_init_control *init_control)
struct vcpu *v;
int rc;
+ /* Fail init_control for domains that cannot use FIFO ABI */
+ if ( d->options & XEN_DOMCTL_CDF_disable_fifo )
+ return -EPERM;
+
init_control->link_bits = EVTCHN_FIFO_LINK_BITS;
vcpu_id = init_control->vcpu;
@@ -64,6 +64,9 @@ struct xen_domctl_createdomain {
/* Is this a xenstore domain? */
#define _XEN_DOMCTL_CDF_xs_domain 4
#define XEN_DOMCTL_CDF_xs_domain (1U<<_XEN_DOMCTL_CDF_xs_domain)
+ /* Disable FIFO event channels? */
+#define _XEN_DOMCTL_CDF_disable_fifo 5
+#define XEN_DOMCTL_CDF_disable_fifo (1U<<_XEN_DOMCTL_CDF_disable_fifo)
uint32_t flags;
/*
Support for FIFO event channel ABI was first introduced in Xen 4.4 (see 88910061ec6). Make this support tunable, since the choice of which event channel ABI has implications for hibernation. Consider resuming a pre Xen 4.4 hibernated Linux guest. During resume from hibernation, there are two kernels involved: the "boot" kernel and the "resume" kernel. The guest boot kernel may default to FIFO ABI and instruct Xen via an EVTCHNOP_init_control to switch from 2L to FIFO. On the other hand, the resume kernel keeps assuming 2L. This, in turn, results in Xen and the resumed kernel talking past each other (due to different protocols FIFO vs 2L). A knob to control the support level for event channel ABIs per guest would allow an administrator to work around this issue. This patch introduces this knob. In order to announce to guests that the event channel ABI does not support FIFO, the hypervisor returns EPERM on init_control operation. When this operation fails, the guest should continue to use the 2L event channel ABI. For example, in Linux drivers/xen/events/events_base.c: if (fifo_events) ret = xen_evtchn_fifo_init(); if (ret < 0) xen_evtchn_2l_init(); and xen_evtchn_fifo_init fails when EVTCHNOP_init_control fails. This commit does not change the current default behaviour: announce FIFO event channels ABI support for guests unless explicitly stated otherwise at domaincreate. Signed-off-by: Eslam Elnikety <elnikety@amazon.com> --- Changes in v2: - Reworded the commit message - Return EPERM instead of ENOSYS when forcing 2L ABI - Use d->options instead of replicating the flag Changes in v3: - Reworded the commit subject - Check at evtchn_fifo_init_control, rather than EVTCHNOP_init_control --- docs/man/xl.cfg.5.pod.in | 5 +++++ tools/libxl/libxl.h | 8 ++++++++ tools/libxl/libxl_create.c | 5 +++++ tools/libxl/libxl_types.idl | 1 + tools/xl/xl_parse.c | 2 ++ tools/xl/xl_sxp.c | 2 ++ xen/common/event_channel.c | 1 + xen/common/event_fifo.c | 4 ++++ xen/include/public/domctl.h | 3 +++ 9 files changed, 31 insertions(+)