Re: [PATCH v5 1/2] xen+tools: Report Interrupt Controller Virtualization capabilities on x86

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Mar 07, 2022 at 03:06:08PM +0000, Jane Malalane wrote:
> Add XEN_SYSCTL_PHYSCAP_ARCH_ASSISTED_xapic and
> XEN_SYSCTL_PHYSCAP_ARCH_ASSISTED_x2apic to report accelerated xapic
> and x2apic, on x86 hardware.

I think the commit message has gone out of sync with the code, those
should now be XEN_SYSCTL_PHYSCAP_X86_ASSISTED_X{2,}APIC

> No such features are currently implemented on AMD hardware.
> 
> HW assisted xAPIC virtualization will be reported if HW, at the
> minimum, supports virtualize_apic_accesses as this feature alone means
> that an access to the APIC page will cause an APIC-access VM exit. An
> APIC-access VM exit provides a VMM with information about the access
> causing the VM exit, unlike a regular EPT fault, thus simplifying some
> internal handling.
> 
> HW assisted x2APIC virtualization will be reported if HW supports
> virtualize_x2apic_mode and, at least, either apic_reg_virt or
> virtual_intr_delivery. This is due to apic_reg_virt and
> virtual_intr_delivery preventing a VM exit from occuring or at least
> replacing a regular EPT fault VM-exit with an APIC-access VM-exit on

For x2APIC there's no EPT fault, because x2APIC accesses are in the
MSR space. I think you can omit this whole sentence and just mention
that this now follows the conditionals in vmx_vlapic_msr_changed.

> read and write APIC accesses, respectively. This also means that
> sysctl follows the conditionals in vmx_vlapic_msr_changed().
> 
> For that purpose, also add an arch-specific "capabilities" parameter
> to struct xen_sysctl_physinfo.
> 
> Note that this interface is intended to be compatible with AMD so that
> AVIC support can be introduced in a future patch. Unlike Intel that
> has multiple controls for APIC Virtualization, AMD has one global
> 'AVIC Enable' control bit, so fine-graining of APIC virtualization
> control cannot be done on a common interface.
> 
> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Jane Malalane <jane.malalane@xxxxxxxxxx>
> ---
> CC: Wei Liu <wl@xxxxxxx>
> CC: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> CC: George Dunlap <george.dunlap@xxxxxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> CC: Julien Grall <julien@xxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> CC: Kevin Tian <kevin.tian@xxxxxxxxx>
> CC: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
> 
> v5:
> * Have assisted_xapic_available solely depend on
>   cpu_has_vmx_virtualize_apic_accesses and assisted_x2apic_available
>   depend on cpu_has_vmx_virtualize_x2apic_mode and
>   cpu_has_vmx_apic_reg_virt OR cpu_has_vmx_virtual_intr_delivery.
> 
> v4:
>  * Fallback to the original v2/v1 conditions for setting
>    assisted_xapic_available and assisted_x2apic_available so that in
>    the future APIC virtualization can be exposed on AMD hardware
>    since fine-graining of "AVIC" is not supported, i.e., AMD solely
>    uses "AVIC Enable". This also means that sysctl mimics what's
>    exposed in CPUID.
> 
> v3:
>  * Define XEN_SYSCTL_PHYSCAP_ARCH_MAX for ABI checking and actually
>    set "arch_capbilities", via a call to c_bitmap_to_ocaml_list()
>  * Have assisted_x2apic_available only depend on
>    cpu_has_vmx_virtualize_x2apic_mode
> 
> v2:
>  * Use one macro LIBXL_HAVE_PHYSINFO_ASSISTED_APIC instead of two
>  * Pass xcpyshinfo as a pointer in libxl__arch_get_physinfo
>  * Set assisted_x{2}apic_available to be conditional upon "bsp" and
>    annotate it with __ro_after_init
>  * Change XEN_SYSCTL_PHYSCAP_ARCH_ASSISTED_X{2}APIC to
>    _X86_ASSISTED_X{2}APIC
>  * Keep XEN_SYSCTL_PHYSCAP_X86_ASSISTED_X{2}APIC contained within
>    sysctl.h
>  * Fix padding introduced in struct xen_sysctl_physinfo and bump
>    XEN_SYSCTL_INTERFACE_VERSION
> ---
>  tools/golang/xenlight/helpers.gen.go |  4 ++++
>  tools/golang/xenlight/types.gen.go   |  2 ++
>  tools/include/libxl.h                |  7 +++++++
>  tools/libs/light/libxl.c             |  3 +++
>  tools/libs/light/libxl_arch.h        |  4 ++++
>  tools/libs/light/libxl_arm.c         |  5 +++++
>  tools/libs/light/libxl_types.idl     |  2 ++
>  tools/libs/light/libxl_x86.c         | 11 +++++++++++
>  tools/ocaml/libs/xc/xenctrl.ml       |  5 +++++
>  tools/ocaml/libs/xc/xenctrl.mli      |  5 +++++
>  tools/ocaml/libs/xc/xenctrl_stubs.c  | 14 +++++++++++---
>  tools/xl/xl_info.c                   |  6 ++++--
>  xen/arch/x86/hvm/vmx/vmcs.c          |  9 +++++++++
>  xen/arch/x86/include/asm/domain.h    |  3 +++
>  xen/arch/x86/sysctl.c                |  7 +++++++
>  xen/include/public/sysctl.h          | 11 ++++++++++-
>  16 files changed, 92 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/golang/xenlight/helpers.gen.go 
> b/tools/golang/xenlight/helpers.gen.go
> index b746ff1081..dd4e6c9f14 100644
> --- a/tools/golang/xenlight/helpers.gen.go
> +++ b/tools/golang/xenlight/helpers.gen.go
> @@ -3373,6 +3373,8 @@ x.CapVmtrace = bool(xc.cap_vmtrace)
>  x.CapVpmu = bool(xc.cap_vpmu)
>  x.CapGnttabV1 = bool(xc.cap_gnttab_v1)
>  x.CapGnttabV2 = bool(xc.cap_gnttab_v2)
> +x.CapAssistedXapic = bool(xc.cap_assisted_xapic)
> +x.CapAssistedX2Apic = bool(xc.cap_assisted_x2apic)
>  
>   return nil}
>  
> @@ -3407,6 +3409,8 @@ xc.cap_vmtrace = C.bool(x.CapVmtrace)
>  xc.cap_vpmu = C.bool(x.CapVpmu)
>  xc.cap_gnttab_v1 = C.bool(x.CapGnttabV1)
>  xc.cap_gnttab_v2 = C.bool(x.CapGnttabV2)
> +xc.cap_assisted_xapic = C.bool(x.CapAssistedXapic)
> +xc.cap_assisted_x2apic = C.bool(x.CapAssistedX2Apic)
>  
>   return nil
>   }
> diff --git a/tools/golang/xenlight/types.gen.go 
> b/tools/golang/xenlight/types.gen.go
> index b1e84d5258..87be46c745 100644
> --- a/tools/golang/xenlight/types.gen.go
> +++ b/tools/golang/xenlight/types.gen.go
> @@ -1014,6 +1014,8 @@ CapVmtrace bool
>  CapVpmu bool
>  CapGnttabV1 bool
>  CapGnttabV2 bool
> +CapAssistedXapic bool
> +CapAssistedX2Apic bool
>  }
>  
>  type Connectorinfo struct {
> diff --git a/tools/include/libxl.h b/tools/include/libxl.h
> index 51a9b6cfac..94e6355822 100644
> --- a/tools/include/libxl.h
> +++ b/tools/include/libxl.h
> @@ -528,6 +528,13 @@
>  #define LIBXL_HAVE_MAX_GRANT_VERSION 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 ABI compatibility
>   *
>   * The only guarantee which libxl makes regarding ABI compatibility
> diff --git a/tools/libs/light/libxl.c b/tools/libs/light/libxl.c
> index a0bf7d186f..6d699951e2 100644
> --- a/tools/libs/light/libxl.c
> +++ b/tools/libs/light/libxl.c
> @@ -15,6 +15,7 @@
>  #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)
> @@ -410,6 +411,8 @@ 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;
>  }
> diff --git a/tools/libs/light/libxl_arch.h b/tools/libs/light/libxl_arch.h
> index 1522ecb97f..207ceac6a1 100644
> --- a/tools/libs/light/libxl_arch.h
> +++ b/tools/libs/light/libxl_arch.h
> @@ -86,6 +86,10 @@ int libxl__arch_extra_memory(libxl__gc *gc,
>                               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,
>                                        const libxl_domain_config *src);
> diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
> index eef1de0939..39fdca1b49 100644
> --- a/tools/libs/light/libxl_arm.c
> +++ b/tools/libs/light/libxl_arm.c
> @@ -1431,6 +1431,11 @@ 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)
> diff --git a/tools/libs/light/libxl_types.idl 
> b/tools/libs/light/libxl_types.idl
> index 2a42da2f7d..42ac6c357b 100644
> --- a/tools/libs/light/libxl_types.idl
> +++ b/tools/libs/light/libxl_types.idl
> @@ -1068,6 +1068,8 @@ 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", [
> diff --git a/tools/libs/light/libxl_x86.c b/tools/libs/light/libxl_x86.c
> index 1feadebb18..e0a06ecfe3 100644
> --- a/tools/libs/light/libxl_x86.c
> +++ b/tools/libs/light/libxl_x86.c
> @@ -866,6 +866,17 @@ 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)
> diff --git a/tools/ocaml/libs/xc/xenctrl.ml b/tools/ocaml/libs/xc/xenctrl.ml
> index 7503031d8f..21783d3622 100644
> --- a/tools/ocaml/libs/xc/xenctrl.ml
> +++ b/tools/ocaml/libs/xc/xenctrl.ml
> @@ -127,6 +127,10 @@ type physinfo_cap_flag =
>       | CAP_Gnttab_v1
>       | CAP_Gnttab_v2
>  
> +type physinfo_arch_cap_flag =
> +     | CAP_X86_ASSISTED_XAPIC
> +     | CAP_X86_ASSISTED_X2APIC
> +
>  type physinfo =
>  {
>       threads_per_core : int;
> @@ -139,6 +143,7 @@ type physinfo =
>       scrub_pages      : nativeint;
>       (* XXX hw_cap *)
>       capabilities     : physinfo_cap_flag list;
> +     arch_capabilities : physinfo_arch_cap_flag list;
>       max_nr_cpus      : int;
>  }
>  
> diff --git a/tools/ocaml/libs/xc/xenctrl.mli b/tools/ocaml/libs/xc/xenctrl.mli
> index d1d9c9247a..af6ba3d1a0 100644
> --- a/tools/ocaml/libs/xc/xenctrl.mli
> +++ b/tools/ocaml/libs/xc/xenctrl.mli
> @@ -112,6 +112,10 @@ type physinfo_cap_flag =
>    | CAP_Gnttab_v1
>    | CAP_Gnttab_v2
>  
> +type physinfo_arch_cap_flag =
> +  | CAP_X86_ASSISTED_XAPIC
> +  | CAP_X86_ASSISTED_X2APIC
> +
>  type physinfo = {
>    threads_per_core : int;
>    cores_per_socket : int;
> @@ -122,6 +126,7 @@ type physinfo = {
>    free_pages       : nativeint;
>    scrub_pages      : nativeint;
>    capabilities     : physinfo_cap_flag list;
> +  arch_capabilities : physinfo_arch_cap_flag list;
>    max_nr_cpus      : int; (** compile-time max possible number of nr_cpus *)
>  }
>  type version = { major : int; minor : int; extra : string; }
> diff --git a/tools/ocaml/libs/xc/xenctrl_stubs.c 
> b/tools/ocaml/libs/xc/xenctrl_stubs.c
> index 5b4fe72c8d..e0d49b18d2 100644
> --- a/tools/ocaml/libs/xc/xenctrl_stubs.c
> +++ b/tools/ocaml/libs/xc/xenctrl_stubs.c
> @@ -712,7 +712,7 @@ CAMLprim value stub_xc_send_debug_keys(value xch, value 
> keys)
>  CAMLprim value stub_xc_physinfo(value xch)
>  {
>       CAMLparam1(xch);
> -     CAMLlocal2(physinfo, cap_list);
> +     CAMLlocal3(physinfo, cap_list, arch_cap_list);
>       xc_physinfo_t c_physinfo;
>       int r;
>  
> @@ -730,8 +730,15 @@ CAMLprim value stub_xc_physinfo(value xch)
>               /* ! physinfo_cap_flag CAP_ lc */
>               /* ! XEN_SYSCTL_PHYSCAP_ XEN_SYSCTL_PHYSCAP_MAX max */
>               (c_physinfo.capabilities);
> +     /*
> +      * arch_capabilities: physinfo_arch_cap_flag list;
> +      */
> +     arch_cap_list = c_bitmap_to_ocaml_list
> +             /* ! physinfo_arch_cap_flag CAP_ none */
> +             /* ! XEN_SYSCTL_PHYSCAP_ XEN_SYSCTL_PHYSCAP_X86_MAX max */
> +             (c_physinfo.arch_capabilities);

Note the above is likely to need adjusting if Arm (or other arches)
start using arch_capabilities. Could we make this conditional to
CONFIG_X86 being enabled?

>  
> -     physinfo = caml_alloc_tuple(10);
> +     physinfo = caml_alloc_tuple(11);
>       Store_field(physinfo, 0, Val_int(c_physinfo.threads_per_core));
>       Store_field(physinfo, 1, Val_int(c_physinfo.cores_per_socket));
>       Store_field(physinfo, 2, Val_int(c_physinfo.nr_cpus));
> @@ -741,7 +748,8 @@ CAMLprim value stub_xc_physinfo(value xch)
>       Store_field(physinfo, 6, caml_copy_nativeint(c_physinfo.free_pages));
>       Store_field(physinfo, 7, caml_copy_nativeint(c_physinfo.scrub_pages));
>       Store_field(physinfo, 8, cap_list);
> -     Store_field(physinfo, 9, Val_int(c_physinfo.max_cpu_id + 1));
> +     Store_field(physinfo, 9, arch_cap_list);
> +     Store_field(physinfo, 10, Val_int(c_physinfo.max_cpu_id + 1));
>  
>       CAMLreturn(physinfo);
>  }
> diff --git a/tools/xl/xl_info.c b/tools/xl/xl_info.c
> index 712b7638b0..3205270754 100644
> --- a/tools/xl/xl_info.c
> +++ b/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\n",
> +    maybe_printf("virt_caps              :%s%s%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" : "",
> @@ -221,7 +221,9 @@ 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_gnttab_v2 ? " gnttab-v2" : "",
> +         info.cap_assisted_xapic ? " assisted_xapic" : "",
> +         info.cap_assisted_x2apic ? " assisted_x2apic" : ""
>          );
>  
>      vinfo = libxl_get_version_info(ctx);
> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> index e1e1fa14e6..06831099ed 100644
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -343,6 +343,15 @@ static int vmx_init_vmcs_config(bool bsp)
>              MSR_IA32_VMX_PROCBASED_CTLS2, &mismatch);
>      }
>  
> +    /* Check whether hardware supports accelerated xapic and x2apic. */
> +    if ( bsp )
> +    {
> +        assisted_xapic_available = cpu_has_vmx_virtualize_apic_accesses;
> +        assisted_x2apic_available = (cpu_has_vmx_virtualize_x2apic_mode &&
> +                                     (cpu_has_vmx_apic_reg_virt ||
> +                                      cpu_has_vmx_virtual_intr_delivery));

There's no need for the outer parentheses.

Thanks, Roger.