diff mbox series

[v4,2/2] x86/xen: Allow per-domain usage of hardware virtualized APIC

Message ID 20220302150056.14381-3-jane.malalane@citrix.com (mailing list archive)
State Superseded
Headers show
Series xen: Report and use hardware APIC virtualization capabilities | expand

Commit Message

Jane Malalane March 2, 2022, 3 p.m. UTC
Introduce a new per-domain creation x86 specific flag to
select whether hardware assisted virtualization should be used for
x{2}APIC.

A per-domain option is added to xl in order to select the usage of
x{2}APIC hardware assisted vitualization, as well as a global
configuration option.

Having all APIC interaction exit to Xen for emulation is slow and can
induce much overhead. Hardware can speed up x{2}APIC by decoding the
APIC access and providing a VM exit with a more specific exit reason
than a regular EPT fault or by altogether avoiding a VM exit.

On the other hand, being able to disable x{2}APIC hardware assisted
vitualization can be useful for testing and debugging purposes.

Note:

- vmx_install_vlapic_mapping doesn't require modifications regardless
  of whether the guest has "Virtualize APIC accesses" enabled or not,
  i.e., setting the the APIC_ACCESS_ADDR VMCS field is fine so long as
  virtualize_apic_accesses is supported by the CPU.

- XEN_HVM_CPUID_XAPIC_VIRT will now also depend on HW supporting
  virtualize_apic_accesses but this addition has no effect since
  apic_reg_virt support, which is currently a requirement for setting
  this CPUID bit, without virtualize_apic_accesses has no effect on
  xAPIC accesses anyway.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jane Malalane <jane.malalane@citrix.com>
---
CC: Wei Liu <wl@xen.org>
CC: Anthony PERARD <anthony.perard@citrix.com>
CC: Juergen Gross <jgross@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: George Dunlap <george.dunlap@citrix.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Julien Grall <julien@xen.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Christian Lindig <christian.lindig@citrix.com>
CC: David Scott <dave@recoil.org>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
CC: "Roger Pau Monné" <roger.pau@citrix.com>

v4:
 * Add has_assisted_x{2}apic macros and use them where appropriate
 * Replace CPU checks with per-domain assisted_x{2}apic control
   options in vmx_vlapic_msr_changed() and cpuid_hypervisor_leaves(),
   following edits to assisted_x{2}apic_available definitions in
   patch 1
   Note: new assisted_x{2}apic_available definitions make later
   cpu_has_vmx_apic_reg_virt and cpu_has_vmx_virtual_intr_delivery
   checks redundant in vmx_vlapic_msr_changed()

v3:
 * Change info in xl.cfg to better express reality and fix
   capitalization of x{2}apic
 * Move "physinfo" variable definition to the beggining of
   libxl__domain_build_info_setdefault()
 * Reposition brackets in if statement to match libxl coding style
 * Shorten logic in libxl__arch_domain_build_info_setdefault()
 * Correct dprintk message in arch_sanitise_domain_config()
 * Make appropriate changes in vmx_vlapic_msr_changed() and
   cpuid_hypervisor_leaves() for amended "assisted_x2apic" bit
 * Remove unneeded parantheses

v2:
 * Add a LIBXL_HAVE_ASSISTED_APIC macro
 * Pass xcpyshinfo as a pointer in libxl__arch_get_physinfo
 * Add a return statement in now "int"
   libxl__arch_domain_build_info_setdefault()
 * Preserve libxl__arch_domain_build_info_setdefault 's location in
   libxl_create.c
 * Correct x{2}apic default setting logic in
   libxl__arch_domain_prepare_config()
 * Correct logic for parsing assisted_x{2}apic host/guest options in
   xl_parse.c and initialize them to -1 in xl.c
 * Use guest options directly in vmx_vlapic_msr_changed
 * Fix indentation of bool assisted_x{2}apic in struct hvm_domain
 * Add a change in xenctrl_stubs.c to pass xenctrl ABI checks
---
 docs/man/xl.cfg.5.pod.in                | 19 ++++++++++++++++
 docs/man/xl.conf.5.pod.in               | 12 ++++++++++
 tools/golang/xenlight/helpers.gen.go    | 12 ++++++++++
 tools/golang/xenlight/types.gen.go      |  2 ++
 tools/include/libxl.h                   |  7 ++++++
 tools/libs/light/libxl_arch.h           |  5 +++--
 tools/libs/light/libxl_arm.c            |  7 ++++--
 tools/libs/light/libxl_create.c         | 22 +++++++++++--------
 tools/libs/light/libxl_types.idl        |  2 ++
 tools/libs/light/libxl_x86.c            | 28 +++++++++++++++++++++--
 tools/ocaml/libs/xc/xenctrl.ml          |  2 ++
 tools/ocaml/libs/xc/xenctrl.mli         |  2 ++
 tools/ocaml/libs/xc/xenctrl_stubs.c     |  2 +-
 tools/xl/xl.c                           |  8 +++++++
 tools/xl/xl.h                           |  2 ++
 tools/xl/xl_parse.c                     | 16 ++++++++++++++
 xen/arch/x86/domain.c                   | 28 ++++++++++++++++++++++-
 xen/arch/x86/hvm/vmx/vmcs.c             |  4 ++++
 xen/arch/x86/hvm/vmx/vmx.c              | 39 +++++++++++++--------------------
 xen/arch/x86/include/asm/hvm/domain.h   |  6 +++++
 xen/arch/x86/include/asm/hvm/vmx/vmcs.h |  3 +++
 xen/arch/x86/traps.c                    |  6 ++---
 xen/include/public/arch-x86/xen.h       |  2 ++
 23 files changed, 191 insertions(+), 45 deletions(-)

Comments

Jan Beulich March 3, 2022, noon UTC | #1
On 02.03.2022 16:00, Jane Malalane wrote:
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -3344,16 +3344,11 @@ static void vmx_install_vlapic_mapping(struct vcpu *v)
>  
>  void vmx_vlapic_msr_changed(struct vcpu *v)
>  {
> -    int virtualize_x2apic_mode;
>      struct vlapic *vlapic = vcpu_vlapic(v);
>      unsigned int msr;
>  
> -    virtualize_x2apic_mode = ( (cpu_has_vmx_apic_reg_virt ||
> -                                cpu_has_vmx_virtual_intr_delivery) &&
> -                               cpu_has_vmx_virtualize_x2apic_mode );
> -
> -    if ( !cpu_has_vmx_virtualize_apic_accesses &&
> -         !virtualize_x2apic_mode )
> +    if ( !has_assisted_xapic(v->domain) &&
> +         !has_assisted_x2apic(v->domain) )
>          return;

This is not an equivalent replacement: The earlier condition was not the
AND of all three sub-features. This is the reason for ...

> @@ -3363,28 +3358,24 @@ void vmx_vlapic_msr_changed(struct vcpu *v)
>      if ( !vlapic_hw_disabled(vlapic) &&
>           (vlapic_base_address(vlapic) == APIC_DEFAULT_PHYS_BASE) )
>      {
> -        if ( virtualize_x2apic_mode && vlapic_x2apic_mode(vlapic) )
> +        if ( has_assisted_x2apic(v->domain) && vlapic_x2apic_mode(vlapic) )
>          {
>              v->arch.hvm.vmx.secondary_exec_control |=
>                  SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE;
> -            if ( cpu_has_vmx_apic_reg_virt )
> -            {
> -                for ( msr = MSR_X2APIC_FIRST;
> -                      msr <= MSR_X2APIC_FIRST + 0xff; msr++ )
> -                    vmx_clear_msr_intercept(v, msr, VMX_MSR_R);
>  
> -                vmx_set_msr_intercept(v, MSR_X2APIC_PPR, VMX_MSR_R);
> -                vmx_set_msr_intercept(v, MSR_X2APIC_TMICT, VMX_MSR_R);
> -                vmx_set_msr_intercept(v, MSR_X2APIC_TMCCT, VMX_MSR_R);
> -            }
> -            if ( cpu_has_vmx_virtual_intr_delivery )
> -            {
> -                vmx_clear_msr_intercept(v, MSR_X2APIC_TPR, VMX_MSR_W);
> -                vmx_clear_msr_intercept(v, MSR_X2APIC_EOI, VMX_MSR_W);
> -                vmx_clear_msr_intercept(v, MSR_X2APIC_SELF, VMX_MSR_W);
> -            }
> +            for ( msr = MSR_X2APIC_FIRST;
> +                  msr <= MSR_X2APIC_FIRST + 0xff; msr++ )
> +                vmx_clear_msr_intercept(v, msr, VMX_MSR_R);
> +
> +            vmx_set_msr_intercept(v, MSR_X2APIC_PPR, VMX_MSR_R);
> +            vmx_set_msr_intercept(v, MSR_X2APIC_TMICT, VMX_MSR_R);
> +            vmx_set_msr_intercept(v, MSR_X2APIC_TMCCT, VMX_MSR_R);
> +
> +            vmx_clear_msr_intercept(v, MSR_X2APIC_TPR, VMX_MSR_W);
> +            vmx_clear_msr_intercept(v, MSR_X2APIC_EOI, VMX_MSR_W);
> +            vmx_clear_msr_intercept(v, MSR_X2APIC_SELF, VMX_MSR_W);
>          }

... you wanting to make these adjustments, but at the same time it means
with certain feature combinations we would now intercept all x2APIC MSR
accesses when some don't need intercepting, which may slow things down
for guests.

Just to be clear - the main part of the discussion imo continues to be
needed on patch 1, to sort what dependencies on features we want where.
One that's clear, what's wanted here should be mostly straightforward.

Jan
diff mbox series

Patch

diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index b98d161398..dcca564a23 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -1862,6 +1862,25 @@  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
+an EPT fault, or altogether avoid a VM exit. Notice full
+virtualization for xAPIC can only be achieved if hardware supports
+“APIC-register virtualization” and “virtual-interrupt delivery”. 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, an MSR-Based APIC access will
+either issue a VM exit or altogether avoid one. Notice full
+virtualization for x2APIC can only be achieved if hardware supports
+“APIC-register virtualization” and “virtual-interrupt delivery”. 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
diff --git a/docs/man/xl.conf.5.pod.in b/docs/man/xl.conf.5.pod.in
index df20c08137..95d136d1ea 100644
--- a/docs/man/xl.conf.5.pod.in
+++ b/docs/man/xl.conf.5.pod.in
@@ -107,6 +107,18 @@  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.
diff --git a/tools/golang/xenlight/helpers.gen.go b/tools/golang/xenlight/helpers.gen.go
index dd4e6c9f14..dece545ee0 100644
--- a/tools/golang/xenlight/helpers.gen.go
+++ b/tools/golang/xenlight/helpers.gen.go
@@ -1120,6 +1120,12 @@  x.ArchArm.Vuart = VuartType(xc.arch_arm.vuart)
 if err := x.ArchX86.MsrRelaxed.fromC(&xc.arch_x86.msr_relaxed);err != nil {
 return fmt.Errorf("converting field ArchX86.MsrRelaxed: %v", err)
 }
+if err := x.ArchX86.AssistedXapic.fromC(&xc.arch_x86.assisted_xapic);err != nil {
+return fmt.Errorf("converting field ArchX86.AssistedXapic: %v", err)
+}
+if err := x.ArchX86.AssistedX2Apic.fromC(&xc.arch_x86.assisted_x2apic);err != nil {
+return fmt.Errorf("converting field ArchX86.AssistedX2Apic: %v", err)
+}
 x.Altp2M = Altp2MMode(xc.altp2m)
 x.VmtraceBufKb = int(xc.vmtrace_buf_kb)
 if err := x.Vpmu.fromC(&xc.vpmu);err != nil {
@@ -1605,6 +1611,12 @@  xc.arch_arm.vuart = C.libxl_vuart_type(x.ArchArm.Vuart)
 if err := x.ArchX86.MsrRelaxed.toC(&xc.arch_x86.msr_relaxed); err != nil {
 return fmt.Errorf("converting field ArchX86.MsrRelaxed: %v", err)
 }
+if err := x.ArchX86.AssistedXapic.toC(&xc.arch_x86.assisted_xapic); err != nil {
+return fmt.Errorf("converting field ArchX86.AssistedXapic: %v", err)
+}
+if err := x.ArchX86.AssistedX2Apic.toC(&xc.arch_x86.assisted_x2apic); err != nil {
+return fmt.Errorf("converting field ArchX86.AssistedX2Apic: %v", err)
+}
 xc.altp2m = C.libxl_altp2m_mode(x.Altp2M)
 xc.vmtrace_buf_kb = C.int(x.VmtraceBufKb)
 if err := x.Vpmu.toC(&xc.vpmu); err != nil {
diff --git a/tools/golang/xenlight/types.gen.go b/tools/golang/xenlight/types.gen.go
index 87be46c745..253c9ad93d 100644
--- a/tools/golang/xenlight/types.gen.go
+++ b/tools/golang/xenlight/types.gen.go
@@ -520,6 +520,8 @@  Vuart VuartType
 }
 ArchX86 struct {
 MsrRelaxed Defbool
+AssistedXapic Defbool
+AssistedX2Apic Defbool
 }
 Altp2M Altp2MMode
 VmtraceBufKb int
diff --git a/tools/include/libxl.h b/tools/include/libxl.h
index 94e6355822..cdcccd6d01 100644
--- a/tools/include/libxl.h
+++ b/tools/include/libxl.h
@@ -535,6 +535,13 @@ 
 #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 ABI compatibility
  *
  * The only guarantee which libxl makes regarding ABI compatibility
diff --git a/tools/libs/light/libxl_arch.h b/tools/libs/light/libxl_arch.h
index 207ceac6a1..03b89929e6 100644
--- a/tools/libs/light/libxl_arch.h
+++ b/tools/libs/light/libxl_arch.h
@@ -71,8 +71,9 @@  void libxl__arch_domain_create_info_setdefault(libxl__gc *gc,
                                                libxl_domain_create_info *c_info);
 
 _hidden
-void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
-                                              libxl_domain_build_info *b_info);
+int libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
+                                             libxl_domain_build_info *b_info,
+                                             const libxl_physinfo *physinfo);
 
 _hidden
 int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index 39fdca1b49..ba5b8f433f 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -1384,8 +1384,9 @@  void libxl__arch_domain_create_info_setdefault(libxl__gc *gc,
     }
 }
 
-void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
-                                              libxl_domain_build_info *b_info)
+int libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
+                                             libxl_domain_build_info *b_info,
+                                             const libxl_physinfo *physinfo)
 {
     /* ACPI is disabled by default */
     libxl_defbool_setdefault(&b_info->acpi, false);
@@ -1399,6 +1400,8 @@  void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
     memset(&b_info->u, '\0', sizeof(b_info->u));
     b_info->type = LIBXL_DOMAIN_TYPE_INVALID;
     libxl_domain_build_info_init_type(b_info, LIBXL_DOMAIN_TYPE_PVH);
+
+    return 0;
 }
 
 int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
diff --git a/tools/libs/light/libxl_create.c b/tools/libs/light/libxl_create.c
index 15ed021f41..88d08d7277 100644
--- a/tools/libs/light/libxl_create.c
+++ b/tools/libs/light/libxl_create.c
@@ -75,6 +75,7 @@  int libxl__domain_build_info_setdefault(libxl__gc *gc,
                                         libxl_domain_build_info *b_info)
 {
     int i, rc;
+    libxl_physinfo info;
 
     if (b_info->type != LIBXL_DOMAIN_TYPE_HVM &&
         b_info->type != LIBXL_DOMAIN_TYPE_PV &&
@@ -264,7 +265,18 @@  int libxl__domain_build_info_setdefault(libxl__gc *gc,
     if (!b_info->event_channels)
         b_info->event_channels = 1023;
 
-    libxl__arch_domain_build_info_setdefault(gc, b_info);
+    rc = libxl_get_physinfo(CTX, &info);
+    if (rc) {
+        LOG(ERROR, "failed to get hypervisor info");
+        return rc;
+    }
+
+    rc = libxl__arch_domain_build_info_setdefault(gc, b_info, &info);
+    if (rc) {
+        LOG(ERROR, "unable to set domain arch build info defaults");
+        return rc;
+    }
+
     libxl_defbool_setdefault(&b_info->dm_restrict, false);
 
     if (b_info->iommu_memkb == LIBXL_MEMKB_DEFAULT)
@@ -457,14 +469,6 @@  int libxl__domain_build_info_setdefault(libxl__gc *gc,
     }
 
     if (b_info->max_grant_version == LIBXL_MAX_GRANT_DEFAULT) {
-        libxl_physinfo info;
-
-        rc = libxl_get_physinfo(CTX, &info);
-        if (rc) {
-            LOG(ERROR, "failed to get hypervisor info");
-            return rc;
-        }
-
         if (info.cap_gnttab_v2)
             b_info->max_grant_version = 2;
         else if (info.cap_gnttab_v1)
diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
index 42ac6c357b..db5eb0a0b3 100644
--- a/tools/libs/light/libxl_types.idl
+++ b/tools/libs/light/libxl_types.idl
@@ -648,6 +648,8 @@  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.
diff --git a/tools/libs/light/libxl_x86.c b/tools/libs/light/libxl_x86.c
index e0a06ecfe3..c377d13b19 100644
--- a/tools/libs/light/libxl_x86.c
+++ b/tools/libs/light/libxl_x86.c
@@ -23,6 +23,14 @@  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;
 }
 
@@ -819,11 +827,27 @@  void libxl__arch_domain_create_info_setdefault(libxl__gc *gc,
 {
 }
 
-void libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
-                                              libxl_domain_build_info *b_info)
+int libxl__arch_domain_build_info_setdefault(libxl__gc *gc,
+                                             libxl_domain_build_info *b_info,
+                                             const libxl_physinfo *physinfo)
 {
     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;
 }
 
 int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
diff --git a/tools/ocaml/libs/xc/xenctrl.ml b/tools/ocaml/libs/xc/xenctrl.ml
index 21783d3622..672a11ceb6 100644
--- a/tools/ocaml/libs/xc/xenctrl.ml
+++ b/tools/ocaml/libs/xc/xenctrl.ml
@@ -50,6 +50,8 @@  type x86_arch_emulation_flags =
 
 type x86_arch_misc_flags =
 	| X86_MSR_RELAXED
+	| X86_ASSISTED_XAPIC
+	| X86_ASSISTED_X2APIC
 
 type xen_x86_arch_domainconfig =
 {
diff --git a/tools/ocaml/libs/xc/xenctrl.mli b/tools/ocaml/libs/xc/xenctrl.mli
index af6ba3d1a0..f9a6aa3a0f 100644
--- a/tools/ocaml/libs/xc/xenctrl.mli
+++ b/tools/ocaml/libs/xc/xenctrl.mli
@@ -44,6 +44,8 @@  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;
diff --git a/tools/ocaml/libs/xc/xenctrl_stubs.c b/tools/ocaml/libs/xc/xenctrl_stubs.c
index e0d49b18d2..ecfc7125d5 100644
--- a/tools/ocaml/libs/xc/xenctrl_stubs.c
+++ b/tools/ocaml/libs/xc/xenctrl_stubs.c
@@ -239,7 +239,7 @@  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_MSR_RELAXED all */
+			/* ! XEN_X86_ XEN_X86_ASSISTED_X2APIC max */
 			(VAL_MISC_FLAGS);
 
 #undef VAL_MISC_FLAGS
diff --git a/tools/xl/xl.c b/tools/xl/xl.c
index 2d1ec18ea3..31eb223309 100644
--- a/tools/xl/xl.c
+++ b/tools/xl/xl.c
@@ -57,6 +57,8 @@  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;
 
@@ -201,6 +203,12 @@  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",
diff --git a/tools/xl/xl.h b/tools/xl/xl.h
index c5c4bedbdd..528deb3feb 100644
--- a/tools/xl/xl.h
+++ b/tools/xl/xl.h
@@ -286,6 +286,8 @@  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,
diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
index 117fcdcb2b..0ab9b145fe 100644
--- a/tools/xl/xl_parse.c
+++ b/tools/xl/xl_parse.c
@@ -1681,6 +1681,22 @@  void parse_config_data(const char *config_source,
         xlu_cfg_get_defbool(config, "vpt_align", &b_info->u.hvm.vpt_align, 0);
         xlu_cfg_get_defbool(config, "apic", &b_info->apic, 0);
 
+        e = xlu_cfg_get_long(config, "assisted_xapic", &l , 0);
+        if ((e == ESRCH && assisted_xapic != -1)) /* use global default if present */
+            libxl_defbool_set(&b_info->arch_x86.assisted_xapic, assisted_xapic);
+        else if (!e)
+            libxl_defbool_set(&b_info->arch_x86.assisted_xapic, l);
+        else
+            exit(1);
+
+        e = xlu_cfg_get_long(config, "assisted_x2apic", &l, 0);
+        if ((e == ESRCH && assisted_x2apic != -1)) /* use global default if present */
+            libxl_defbool_set(&b_info->arch_x86.assisted_x2apic, assisted_x2apic);
+        else if (!e)
+            libxl_defbool_set(&b_info->arch_x86.assisted_x2apic, l);
+        else
+            exit(1);
+
         switch (xlu_cfg_get_list(config, "viridian",
                                  &viridian, &num_viridian, 1))
         {
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index a5048ed654..bcca0dc900 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -619,6 +619,8 @@  int arch_sanitise_domain_config(struct xen_domctl_createdomain *config)
     bool hvm = config->flags & XEN_DOMCTL_CDF_hvm;
     bool hap = config->flags & XEN_DOMCTL_CDF_hap;
     bool nested_virt = config->flags & XEN_DOMCTL_CDF_nested_virt;
+    bool assisted_xapic = config->arch.misc_flags & XEN_X86_ASSISTED_XAPIC;
+    bool assisted_x2apic = config->arch.misc_flags & XEN_X86_ASSISTED_X2APIC;
     unsigned int max_vcpus;
 
     if ( hvm ? !hvm_enabled : !IS_ENABLED(CONFIG_PV) )
@@ -685,13 +687,31 @@  int arch_sanitise_domain_config(struct xen_domctl_createdomain *config)
         }
     }
 
-    if ( config->arch.misc_flags & ~XEN_X86_MSR_RELAXED )
+    if ( config->arch.misc_flags & ~(XEN_X86_MSR_RELAXED |
+                                     XEN_X86_ASSISTED_XAPIC |
+                                     XEN_X86_ASSISTED_X2APIC) )
     {
         dprintk(XENLOG_INFO, "Invalid arch misc flags %#x\n",
                 config->arch.misc_flags);
         return -EINVAL;
     }
 
+    if ( (assisted_xapic || assisted_x2apic) && !hvm )
+    {
+        dprintk(XENLOG_INFO,
+                "Interrupt Controller Virtualization not supported for PV\n");
+        return -EINVAL;
+    }
+
+    if ( (assisted_xapic && !assisted_xapic_available) ||
+         (assisted_x2apic && !assisted_x2apic_available) )
+    {
+        dprintk(XENLOG_INFO,
+                "Hardware assisted x%sAPIC requested but not available\n",
+                assisted_xapic && !assisted_xapic_available ? "" : "2");
+        return -EINVAL;
+    }
+
     return 0;
 }
 
@@ -864,6 +884,12 @@  int arch_domain_create(struct domain *d,
 
     d->arch.msr_relaxed = config->arch.misc_flags & XEN_X86_MSR_RELAXED;
 
+    d->arch.hvm.assisted_xapic =
+        config->arch.misc_flags & XEN_X86_ASSISTED_XAPIC;
+
+    d->arch.hvm.assisted_x2apic =
+        config->arch.misc_flags & XEN_X86_ASSISTED_X2APIC;
+
     return 0;
 
  fail:
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 6f1fec49b9..e8cb7792dc 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1158,6 +1158,10 @@  static int construct_vmcs(struct vcpu *v)
         __vmwrite(PLE_WINDOW, ple_window);
     }
 
+    if ( !has_assisted_xapic(v->domain) )
+        v->arch.hvm.vmx.secondary_exec_control &=
+            ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
+
     if ( cpu_has_vmx_secondary_exec_control )
         __vmwrite(SECONDARY_VM_EXEC_CONTROL,
                   v->arch.hvm.vmx.secondary_exec_control);
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index c075370f64..73c7ae1e84 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3344,16 +3344,11 @@  static void vmx_install_vlapic_mapping(struct vcpu *v)
 
 void vmx_vlapic_msr_changed(struct vcpu *v)
 {
-    int virtualize_x2apic_mode;
     struct vlapic *vlapic = vcpu_vlapic(v);
     unsigned int msr;
 
-    virtualize_x2apic_mode = ( (cpu_has_vmx_apic_reg_virt ||
-                                cpu_has_vmx_virtual_intr_delivery) &&
-                               cpu_has_vmx_virtualize_x2apic_mode );
-
-    if ( !cpu_has_vmx_virtualize_apic_accesses &&
-         !virtualize_x2apic_mode )
+    if ( !has_assisted_xapic(v->domain) &&
+         !has_assisted_x2apic(v->domain) )
         return;
 
     vmx_vmcs_enter(v);
@@ -3363,28 +3358,24 @@  void vmx_vlapic_msr_changed(struct vcpu *v)
     if ( !vlapic_hw_disabled(vlapic) &&
          (vlapic_base_address(vlapic) == APIC_DEFAULT_PHYS_BASE) )
     {
-        if ( virtualize_x2apic_mode && vlapic_x2apic_mode(vlapic) )
+        if ( has_assisted_x2apic(v->domain) && vlapic_x2apic_mode(vlapic) )
         {
             v->arch.hvm.vmx.secondary_exec_control |=
                 SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE;
-            if ( cpu_has_vmx_apic_reg_virt )
-            {
-                for ( msr = MSR_X2APIC_FIRST;
-                      msr <= MSR_X2APIC_FIRST + 0xff; msr++ )
-                    vmx_clear_msr_intercept(v, msr, VMX_MSR_R);
 
-                vmx_set_msr_intercept(v, MSR_X2APIC_PPR, VMX_MSR_R);
-                vmx_set_msr_intercept(v, MSR_X2APIC_TMICT, VMX_MSR_R);
-                vmx_set_msr_intercept(v, MSR_X2APIC_TMCCT, VMX_MSR_R);
-            }
-            if ( cpu_has_vmx_virtual_intr_delivery )
-            {
-                vmx_clear_msr_intercept(v, MSR_X2APIC_TPR, VMX_MSR_W);
-                vmx_clear_msr_intercept(v, MSR_X2APIC_EOI, VMX_MSR_W);
-                vmx_clear_msr_intercept(v, MSR_X2APIC_SELF, VMX_MSR_W);
-            }
+            for ( msr = MSR_X2APIC_FIRST;
+                  msr <= MSR_X2APIC_FIRST + 0xff; msr++ )
+                vmx_clear_msr_intercept(v, msr, VMX_MSR_R);
+
+            vmx_set_msr_intercept(v, MSR_X2APIC_PPR, VMX_MSR_R);
+            vmx_set_msr_intercept(v, MSR_X2APIC_TMICT, VMX_MSR_R);
+            vmx_set_msr_intercept(v, MSR_X2APIC_TMCCT, VMX_MSR_R);
+
+            vmx_clear_msr_intercept(v, MSR_X2APIC_TPR, VMX_MSR_W);
+            vmx_clear_msr_intercept(v, MSR_X2APIC_EOI, VMX_MSR_W);
+            vmx_clear_msr_intercept(v, MSR_X2APIC_SELF, VMX_MSR_W);
         }
-        else
+        else if ( has_assisted_xapic(v->domain) )
             v->arch.hvm.vmx.secondary_exec_control |=
                 SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
     }
diff --git a/xen/arch/x86/include/asm/hvm/domain.h b/xen/arch/x86/include/asm/hvm/domain.h
index 698455444e..92bf53483c 100644
--- a/xen/arch/x86/include/asm/hvm/domain.h
+++ b/xen/arch/x86/include/asm/hvm/domain.h
@@ -117,6 +117,12 @@  struct hvm_domain {
 
     bool                   is_s3_suspended;
 
+    /* xAPIC hardware assisted virtualization. */
+    bool                   assisted_xapic;
+
+    /* x2APIC hardware assisted virtualization. */
+    bool                   assisted_x2apic;
+
     /* hypervisor intercepted msix table */
     struct list_head       msixtbl_list;
 
diff --git a/xen/arch/x86/include/asm/hvm/vmx/vmcs.h b/xen/arch/x86/include/asm/hvm/vmx/vmcs.h
index 9119aa8536..5b7d662ed7 100644
--- a/xen/arch/x86/include/asm/hvm/vmx/vmcs.h
+++ b/xen/arch/x86/include/asm/hvm/vmx/vmcs.h
@@ -220,6 +220,9 @@  void vmx_vmcs_reload(struct vcpu *v);
 #define CPU_BASED_ACTIVATE_SECONDARY_CONTROLS 0x80000000
 extern u32 vmx_cpu_based_exec_control;
 
+#define has_assisted_xapic(d)   ((d)->arch.hvm.assisted_xapic)
+#define has_assisted_x2apic(d)  ((d)->arch.hvm.assisted_x2apic)
+
 #define PIN_BASED_EXT_INTR_MASK         0x00000001
 #define PIN_BASED_NMI_EXITING           0x00000008
 #define PIN_BASED_VIRTUAL_NMIS          0x00000020
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index a2278d9499..577c1a3b21 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1121,7 +1121,7 @@  void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t leaf,
         if ( !is_hvm_domain(d) || subleaf != 0 )
             break;
 
-        if ( cpu_has_vmx_apic_reg_virt )
+        if ( has_assisted_xapic(d) )
             res->a |= XEN_HVM_CPUID_APIC_ACCESS_VIRT;
 
         /*
@@ -1130,9 +1130,7 @@  void cpuid_hypervisor_leaves(const struct vcpu *v, uint32_t leaf,
          * and wrmsr in the guest will run without VMEXITs (see
          * vmx_vlapic_msr_changed()).
          */
-        if ( cpu_has_vmx_virtualize_x2apic_mode &&
-             cpu_has_vmx_apic_reg_virt &&
-             cpu_has_vmx_virtual_intr_delivery )
+        if ( has_assisted_x2apic(d) )
             res->a |= XEN_HVM_CPUID_X2APIC_VIRT;
 
         /*
diff --git a/xen/include/public/arch-x86/xen.h b/xen/include/public/arch-x86/xen.h
index 7acd94c8eb..9da32c6239 100644
--- a/xen/include/public/arch-x86/xen.h
+++ b/xen/include/public/arch-x86/xen.h
@@ -317,6 +317,8 @@  struct xen_arch_domainconfig {
  * doesn't allow the guest to read or write to the underlying MSR.
  */
 #define XEN_X86_MSR_RELAXED (1u << 0)
+#define XEN_X86_ASSISTED_XAPIC (1u << 1)
+#define XEN_X86_ASSISTED_X2APIC (1u << 2)
     uint32_t misc_flags;
 };