On Tue, Mar 08, 2022 at 05:36:43PM +0000, Jane Malalane wrote:
> 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 virtualization, 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
> virtualization 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 APIC_ACCESS_ADDR VMCS field is fine so long
> as virtualize_apic_accesses is supported by the CPU.
>
> Suggested-by: Andrew Cooper <andrew.coop...@citrix.com>
> Signed-off-by: Jane Malalane <jane.malal...@citrix.com>
> ---
> CC: Wei Liu <w...@xen.org>
> CC: Anthony PERARD <anthony.per...@citrix.com>
> CC: Juergen Gross <jgr...@suse.com>
> CC: Andrew Cooper <andrew.coop...@citrix.com>
> CC: George Dunlap <george.dun...@citrix.com>
> CC: Jan Beulich <jbeul...@suse.com>
> CC: Julien Grall <jul...@xen.org>
> CC: Stefano Stabellini <sstabell...@kernel.org>
> CC: Christian Lindig <christian.lin...@citrix.com>
> CC: David Scott <d...@recoil.org>
> CC: Volodymyr Babchuk <volodymyr_babc...@epam.com>
> CC: "Roger Pau Monné" <roger....@citrix.com>
>
> v6:
> * Use ENODEV instead of EINVAL when rejecting assisted_x{2}apic
> for PV guests
> * Move has_assisted_x{2}apic macros out of an Intel specific header
> * Remove references to Intel specific features in documentation
>
> v5:
> * Revert v4 changes in vmx_vlapic_msr_changed(), preserving the use of
> the has_assisted_x{2}apic macros
> * Following changes in assisted_x{2}apic_available definitions in
> patch 1, retighten conditionals for setting
> XEN_HVM_CPUID_APIC_ACCESS_VIRT and XEN_HVM_CPUID_X2APIC_VIRT in
> cpuid_hypervisor_leaves()
>
> 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 | 15 +++++++++++++++
> 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 | 27 +++++++++++++++++++++++++--
> 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 | 13 ++++---------
> xen/arch/x86/include/asm/hvm/domain.h | 6 ++++++
> xen/arch/x86/include/asm/hvm/hvm.h | 6 ++++++
> xen/arch/x86/traps.c | 5 +++--
> xen/include/public/arch-x86/xen.h | 2 ++
> 23 files changed, 179 insertions(+), 28 deletions(-)
>
> diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
> index b98d161398..b4239fcc5e 100644
> --- a/docs/man/xl.cfg.5.pod.in
> +++ b/docs/man/xl.cfg.5.pod.in
> @@ -1862,6 +1862,21 @@ 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. The
> +default is settable via L<xl.conf(5)>.
Sorry, replied to a v2 version of the patch instead of this one. Could
we use 'p2m fault' or maybe 'guest physmap fault' intead of EPT (as
that's Intel specific).
Thanks, Roger.
