x86/hvm: Revert per-domain APIC acceleration support

I was really hoping to avoid this, but its now too late in the 4.17 freeze and
we still don't have working fixes.

The in-Xen calculations for assistance capabilities are buggy.  For the
avoidance of doubt, the original intention was to be able to control every
aspect of a APIC acceleration so we could comprehensively test Xen's support,
as it has proved to be buggy time and time again.

Even after a protracted discussion on what the new API ought to mean, attempts
to apply it to the existing logic have been unsuccessful, proving that the
API/ABI is too complicated for most people to reason about.

This reverts most of:
  2ce11ce
  6b2b9b3

leaving in place the non-APIC specific changes (minimal as they are).

This takes us back to the behaviour of Xen 4.16 where APIC acceleration is
configured on a per system basis.

This work will be revisted in due course.

Fixes: 2ce11ce ("x86/HVM: allow per-domain usage of hardware virtualized APIC")
Fixes: 6b2b9b3 ("x86: report Interrupt Controller Virtualization capabilities")
Signed-off-by: Andrew Cooper <[email protected]>
Acked-by: Jan Beulich <[email protected]>
Release-acked-by: Henry Wang <[email protected]>

docs/man/xl.cfg.5.pod.in

@@ -1862,21 +1862,6 @@ firmware tables when using certain older guest Operating
 Systems. These tables have been superseded by newer constructs within
 the ACPI tables.
 
-=item B<assisted_xapic=BOOLEAN>
-
-B<(x86 only)> Enables or disables hardware assisted virtualization for
-xAPIC. With this option enabled, a memory-mapped APIC access will be
-decoded by hardware and either issue a more specific VM exit than just
-a p2m fault, or altogether avoid a VM exit. The
-default is settable via L<xl.conf(5)>.
-
-=item B<assisted_x2apic=BOOLEAN>
-
-B<(x86 only)> Enables or disables hardware assisted virtualization for
-x2APIC. With this option enabled, certain accesses to MSR APIC
-registers will avoid a VM exit into the hypervisor. The default is
-settable via L<xl.conf(5)>.
-
 =item B<nx=BOOLEAN>
 
 B<(x86 only)> Hides or exposes the No-eXecute capability. This allows a guest

docs/man/xl.conf.5.pod.in

@@ -107,18 +107,6 @@ Sets the default value for the C<max_grant_version> domain config value.
 
 Default: maximum grant version supported by the hypervisor.
 
-=item B<assisted_xapic=BOOLEAN>
-
-If enabled, domains will use xAPIC hardware assisted virtualization by default.
-
-Default: enabled if supported.
-
-=item B<assisted_x2apic=BOOLEAN>
-
-If enabled, domains will use x2APIC hardware assisted virtualization by default.
-
-Default: enabled if supported.
-
 =item B<vif.default.script="PATH">
 
 Configures the default hotplug script used by virtual network devices.

tools/include/libxl.h

@@ -535,20 +535,6 @@
 #define LIBXL_HAVE_DISK_TRUSTED 1
 #define LIBXL_HAVE_NIC_TRUSTED 1
 
-/*
- * LIBXL_HAVE_PHYSINFO_ASSISTED_APIC indicates that libxl_physinfo has
- * cap_assisted_xapic and cap_assisted_x2apic fields, which indicates
- * the availability of x{2}APIC hardware assisted virtualization.
- */
-#define LIBXL_HAVE_PHYSINFO_ASSISTED_APIC 1
-
-/*
- * LIBXL_HAVE_ASSISTED_APIC indicates that libxl_domain_build_info has
- * assisted_xapic and assisted_x2apic fields for enabling hardware
- * assisted virtualization for x{2}apic per domain.
- */
-#define LIBXL_HAVE_ASSISTED_APIC 1
-
 /*
  * LIBXL_HAVE_DEVICE_DISK_SPECIFICATION indicates that 'specification' and
  * 'transport' fields (of libxl_disk_specification and libxl_disk_transport

tools/libs/light/libxl.c

@@ -15,7 +15,6 @@
 #include "libxl_osdeps.h"
 
 #include "libxl_internal.h"
-#include "libxl_arch.h"
 
 int libxl_ctx_alloc(libxl_ctx **pctx, int version,
                     unsigned flags, xentoollog_logger * lg)
@@ -411,8 +410,6 @@ int libxl_get_physinfo(libxl_ctx *ctx, libxl_physinfo *physinfo)
     physinfo->cap_gnttab_v2 =
         !!(xcphysinfo.capabilities & XEN_SYSCTL_PHYSCAP_gnttab_v2);
 
-    libxl__arch_get_physinfo(physinfo, &xcphysinfo);
-
     GC_FREE;
     return 0;
 }

tools/libs/light/libxl_arch.h

@@ -86,10 +86,6 @@ int libxl__arch_extra_memory(libxl__gc *gc,
                              const libxl_domain_build_info *info,
                              uint64_t *out);
 
-_hidden
-void libxl__arch_get_physinfo(libxl_physinfo *physinfo,
-                              const xc_physinfo_t *xcphysinfo);
-
 _hidden
 void libxl__arch_update_domain_config(libxl__gc *gc,
                                       libxl_domain_config *dst,

tools/libs/light/libxl_arm.c

@@ -1606,11 +1606,6 @@ int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
     return rc;
 }
 
-void libxl__arch_get_physinfo(libxl_physinfo *physinfo,
-                              const xc_physinfo_t *xcphysinfo)
-{
-}
-
 void libxl__arch_update_domain_config(libxl__gc *gc,
                                       libxl_domain_config *dst,
                                       const libxl_domain_config *src)

tools/libs/light/libxl_types.idl

@@ -660,8 +660,6 @@ libxl_domain_build_info = Struct("domain_build_info",[
                                ("vuart", libxl_vuart_type),
                               ])),
     ("arch_x86", Struct(None, [("msr_relaxed", libxl_defbool),
-                               ("assisted_xapic", libxl_defbool),
-                               ("assisted_x2apic", libxl_defbool),
                               ])),
     # Alternate p2m is not bound to any architecture or guest type, as it is
     # supported by x86 HVM and ARM support is planned.
@@ -1090,8 +1088,6 @@ libxl_physinfo = Struct("physinfo", [
     ("cap_vpmu", bool),
     ("cap_gnttab_v1", bool),
     ("cap_gnttab_v2", bool),
-    ("cap_assisted_xapic", bool),
-    ("cap_assisted_x2apic", bool),
     ], dir=DIR_OUT)
 
 libxl_connectorinfo = Struct("connectorinfo", [

tools/libs/light/libxl_x86.c

@@ -23,15 +23,6 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
     if (libxl_defbool_val(d_config->b_info.arch_x86.msr_relaxed))
         config->arch.misc_flags |= XEN_X86_MSR_RELAXED;
 
-    if (d_config->c_info.type != LIBXL_DOMAIN_TYPE_PV)
-    {
-        if (libxl_defbool_val(d_config->b_info.arch_x86.assisted_xapic))
-            config->arch.misc_flags |= XEN_X86_ASSISTED_XAPIC;
-
-        if (libxl_defbool_val(d_config->b_info.arch_x86.assisted_x2apic))
-            config->arch.misc_flags |= XEN_X86_ASSISTED_X2APIC;
-    }
-
     return 0;
 }
 
@@ -835,18 +826,6 @@ int libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
     libxl_defbool_setdefault(&b_info->acpi, true);
     libxl_defbool_setdefault(&b_info->arch_x86.msr_relaxed, false);
 
-    if (b_info->type != LIBXL_DOMAIN_TYPE_PV) {
-        libxl_defbool_setdefault(&b_info->arch_x86.assisted_xapic,
-                                 physinfo->cap_assisted_xapic);
-        libxl_defbool_setdefault(&b_info->arch_x86.assisted_x2apic,
-                                 physinfo->cap_assisted_x2apic);
-    }
-    else if (!libxl_defbool_is_default(b_info->arch_x86.assisted_xapic) ||
-             !libxl_defbool_is_default(b_info->arch_x86.assisted_x2apic)) {
-        LOG(ERROR, "Interrupt Controller Virtualization not supported for PV");
-        return ERROR_INVAL;
-    }
-
     return 0;
 }
 
@@ -890,17 +869,6 @@ int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
     return rc;
 }
 
-void libxl__arch_get_physinfo(libxl_physinfo *physinfo,
-                              const xc_physinfo_t *xcphysinfo)
-{
-    physinfo->cap_assisted_xapic =
-        !!(xcphysinfo->arch_capabilities &
-           XEN_SYSCTL_PHYSCAP_X86_ASSISTED_XAPIC);
-    physinfo->cap_assisted_x2apic =
-        !!(xcphysinfo->arch_capabilities &
-           XEN_SYSCTL_PHYSCAP_X86_ASSISTED_X2APIC);
-}
-
 void libxl__arch_update_domain_config(libxl__gc *gc,
                                       libxl_domain_config *dst,
                                       const libxl_domain_config *src)

tools/ocaml/libs/xc/xenctrl.ml

@@ -50,8 +50,6 @@ type x86_arch_emulation_flags =
 
 type x86_arch_misc_flags =
 	| X86_MSR_RELAXED
-	| X86_ASSISTED_XAPIC
-	| X86_ASSISTED_X2APIC
 
 type xen_x86_arch_domainconfig =
 {
@@ -132,9 +130,7 @@ type physinfo_cap_flag =
 
 type arm_physinfo_cap_flag
 
-type x86_physinfo_cap_flag =
-	| CAP_X86_ASSISTED_XAPIC
-	| CAP_X86_ASSISTED_X2APIC
+type x86_physinfo_cap_flag
 
 type arch_physinfo_cap_flags =
 	| ARM of arm_physinfo_cap_flag list

tools/ocaml/libs/xc/xenctrl.mli

@@ -44,8 +44,6 @@ type x86_arch_emulation_flags =
 
 type x86_arch_misc_flags =
   | X86_MSR_RELAXED
-  | X86_ASSISTED_XAPIC
-  | X86_ASSISTED_X2APIC
 
 type xen_x86_arch_domainconfig = {
   emulation_flags: x86_arch_emulation_flags list;
@@ -117,9 +115,7 @@ type physinfo_cap_flag =
 
 type arm_physinfo_cap_flag
 
-type x86_physinfo_cap_flag =
-  | CAP_X86_ASSISTED_XAPIC
-  | CAP_X86_ASSISTED_X2APIC
+type x86_physinfo_cap_flag
 
 type arch_physinfo_cap_flags =
   | ARM of arm_physinfo_cap_flag list

tools/ocaml/libs/xc/xenctrl_stubs.c

@@ -241,7 +241,7 @@ CAMLprim value stub_xc_domain_create(value xch, value wanted_domid, value config
 
 		cfg.arch.misc_flags = ocaml_list_to_c_bitmap
 			/* ! x86_arch_misc_flags X86_ none */
-			/* ! XEN_X86_ XEN_X86_MISC_FLAGS_MAX max */
+			/* ! XEN_X86_ XEN_X86_MSR_RELAXED all */
 			(VAL_MISC_FLAGS);
 
 #undef VAL_MISC_FLAGS
@@ -748,10 +748,7 @@ CAMLprim value stub_xc_physinfo(value xch)
 	Store_field(physinfo, 9, Val_int(c_physinfo.max_cpu_id + 1));
 
 #if defined(__i386__) || defined(__x86_64__)
-	arch_cap_list = c_bitmap_to_ocaml_list
-		/* ! x86_physinfo_cap_flag CAP_X86_ none */
-		/* ! XEN_SYSCTL_PHYSCAP_X86_ XEN_SYSCTL_PHYSCAP_X86_MAX max */
-		(c_physinfo.arch_capabilities);
+	arch_cap_list = Tag_cons;
 
 	arch_cap_flags_tag = 1; /* tag x86 */
 #else

tools/xl/xl.c

@@ -57,8 +57,6 @@ int max_grant_frames = -1;
 int max_maptrack_frames = -1;
 int max_grant_version = LIBXL_MAX_GRANT_DEFAULT;
 libxl_domid domid_policy = INVALID_DOMID;
-int assisted_xapic = -1;
-int assisted_x2apic = -1;
 
 xentoollog_level minmsglevel = minmsglevel_default;
 
@@ -203,12 +201,6 @@ static void parse_global_config(const char *configfile,
     if (!xlu_cfg_get_long (config, "claim_mode", &l, 0))
         claim_mode = l;
 
-    if (!xlu_cfg_get_long (config, "assisted_xapic", &l, 0))
-        assisted_xapic = l;
-
-    if (!xlu_cfg_get_long (config, "assisted_x2apic", &l, 0))
-        assisted_x2apic = l;
-
     xlu_cfg_replace_string (config, "remus.default.netbufscript",
         &default_remus_netbufscript, 0);
     xlu_cfg_replace_string (config, "colo.default.proxyscript",

tools/xl/xl.h

@@ -285,8 +285,6 @@ extern libxl_bitmap global_vm_affinity_mask;
 extern libxl_bitmap global_hvm_affinity_mask;
 extern libxl_bitmap global_pv_affinity_mask;
 extern libxl_domid domid_policy;
-extern int assisted_xapic;
-extern int assisted_x2apic;
 
 enum output_format {
     OUTPUT_FORMAT_JSON,

tools/xl/xl_info.c

@@ -210,7 +210,7 @@ static void output_physinfo(void)
          info.hw_cap[4], info.hw_cap[5], info.hw_cap[6], info.hw_cap[7]
         );
 
-    maybe_printf("virt_caps              :%s%s%s%s%s%s%s%s%s%s%s%s%s\n",
+    maybe_printf("virt_caps              :%s%s%s%s%s%s%s%s%s%s%s\n",
          info.cap_pv ? " pv" : "",
          info.cap_hvm ? " hvm" : "",
          info.cap_hvm && info.cap_hvm_directio ? " hvm_directio" : "",
@@ -221,9 +221,7 @@ static void output_physinfo(void)
          info.cap_vmtrace ? " vmtrace" : "",
          info.cap_vpmu ? " vpmu" : "",
          info.cap_gnttab_v1 ? " gnttab-v1" : "",
-         info.cap_gnttab_v2 ? " gnttab-v2" : "",
-         info.cap_assisted_xapic ? " assisted_xapic" : "",
-         info.cap_assisted_x2apic ? " assisted_x2apic" : ""
+         info.cap_gnttab_v2 ? " gnttab-v2" : ""
         );
 
     vinfo = libxl_get_version_info(ctx);

tools/xl/xl_parse.c

@@ -2765,25 +2765,6 @@ void parse_config_data(const char *config_source,
 
     xlu_cfg_get_defbool(config, "vpmu", &b_info->vpmu, 0);
 
-    if (b_info->type != LIBXL_DOMAIN_TYPE_PV) {
-        e = xlu_cfg_get_long(config, "assisted_xapic", &l , 0);
-        if (!e)
-            libxl_defbool_set(&b_info->arch_x86.assisted_xapic, l);
-        else if (e != ESRCH)
-            exit(1);
-        else if (assisted_xapic != -1) /* use global default if present */
-            libxl_defbool_set(&b_info->arch_x86.assisted_xapic, assisted_xapic);
-
-        e = xlu_cfg_get_long(config, "assisted_x2apic", &l, 0);
-        if (!e)
-            libxl_defbool_set(&b_info->arch_x86.assisted_x2apic, l);
-        else if (e != ESRCH)
-            exit(1);
-        else if (assisted_x2apic != -1) /* use global default if present */
-            libxl_defbool_set(&b_info->arch_x86.assisted_x2apic,
-                              assisted_x2apic);
-    }
-
     xlu_cfg_destroy(config);
 }