Re: [PATCH v7 00/12] SVE feature for arm guests

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

> On 23 May 2023, at 08:43, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
> 
> This serie is introducing the possibility for Dom0 and DomU guests to use
> sve/sve2 instructions.
> 
> SVE feature introduces new instruction and registers to improve performances 
> on
> floating point operations.
> 
> The SVE feature is advertised using the ID_AA64PFR0_EL1 register, SVE field, 
> and
> when available the ID_AA64ZFR0_EL1 register provides additional information
> about the implemented version and other SVE feature.
> 
> New registers added by the SVE feature are Z0-Z31, P0-P15, FFR, ZCR_ELx.
> 
> Z0-Z31 are scalable vector register whose size is implementation defined and
> goes from 128 bits to maximum 2048, the term vector length will be used to 
> refer
> to this quantity.
> P0-P15 are predicate registers and the size is the vector length divided by 8,
> same size is the FFR (First Fault Register).
> ZCR_ELx is a register that can control and restrict the maximum vector length
> used by the <x> exception level and all the lower exception levels, so for
> example EL3 can restrict the vector length usable by EL3,2,1,0.
> 
> The platform has a maximum implemented vector length, so for every value
> written in ZCR register, if this value is above the implemented length, then 
> the
> lower value will be used. The RDVL instruction can be used to check what 
> vector
> length is the HW using after setting ZCR.
> 
> For an SVE guest, the V0-V31 registers are part of the Z0-Z31, so there is no
> need to save them separately, saving Z0-Z31 will save implicitly also V0-V31.
> 
> SVE usage can be trapped using a flag in CPTR_EL2, hence in this serie the
> register is added to the domain state, to be able to trap only the guests that
> are not allowed to use SVE.
> 
> This serie is introducing a command line parameter to enable Dom0 to use SVE 
> and
> to set its maximum vector length that by default is 0 which means the guest is
> not allowed to use SVE. Values from 128 to 2048 mean the guest can use SVE 
> with
> the selected value used as maximum allowed vector length (which could be lower
> if the implemented one is lower).
> For DomUs, an XL parameter with the same way of use is introduced and a 
> dom0less
> DTB binding is created.
> 
> The context switch is the most critical part because there can be big 
> registers
> to be saved, in this serie an easy approach is used and the context is
> saved/restored every time for the guests that are allowed to use SVE.
> 
> Luca Fancellu (12):
>  xen/arm: enable SVE extension for Xen
>  xen/arm: add SVE vector length field to the domain
>  xen/arm: Expose SVE feature to the guest
>  xen/arm: add SVE exception class handling
>  arm/sve: save/restore SVE context switch
>  xen/common: add dom0 xen command line argument for Arm
>  xen: enable Dom0 to use SVE feature
>  xen/physinfo: encode Arm SVE vector length in arch_capabilities
>  tools: add physinfo arch_capabilities handling for Arm
>  xen/tools: add sve parameter in XL configuration
>  xen/arm: add sve property for dom0less domUs
>  xen/changelog: Add SVE and "dom0" options to the changelog for Arm
> 
> CHANGELOG.md                                  |   3 +
> SUPPORT.md                                    |   6 +
> docs/man/xl.cfg.5.pod.in                      |  16 ++
> docs/misc/arm/device-tree/booting.txt         |  16 ++
> docs/misc/xen-command-line.pandoc             |  20 +-
> tools/golang/xenlight/helpers.gen.go          |   4 +
> tools/golang/xenlight/types.gen.go            |  24 +++
> tools/include/libxl.h                         |  11 +
> .../include/xen-tools/arm-arch-capabilities.h |  28 +++
> tools/include/xen-tools/common-macros.h       |   2 +
> tools/libs/light/libxl.c                      |   1 +
> tools/libs/light/libxl_arm.c                  |  33 +++
> tools/libs/light/libxl_internal.h             |   1 -
> tools/libs/light/libxl_types.idl              |  23 +++
> tools/ocaml/libs/xc/xenctrl.ml                |   4 +-
> tools/ocaml/libs/xc/xenctrl.mli               |   4 +-
> tools/ocaml/libs/xc/xenctrl_stubs.c           |   8 +-
> tools/python/xen/lowlevel/xc/xc.c             |   8 +-
> tools/xl/xl_info.c                            |   8 +
> tools/xl/xl_parse.c                           |   8 +
> xen/arch/arm/Kconfig                          |  10 +-
> xen/arch/arm/README.LinuxPrimitives           |  11 +
> xen/arch/arm/arm64/Makefile                   |   1 +
> xen/arch/arm/arm64/cpufeature.c               |   7 +-
> xen/arch/arm/arm64/domctl.c                   |   4 +
> xen/arch/arm/arm64/sve-asm.S                  | 195 ++++++++++++++++++
> xen/arch/arm/arm64/sve.c                      | 182 ++++++++++++++++
> xen/arch/arm/arm64/vfp.c                      |  79 ++++---
> xen/arch/arm/arm64/vsysreg.c                  |  41 +++-
> xen/arch/arm/cpufeature.c                     |   6 +-
> xen/arch/arm/domain.c                         |  55 ++++-
> xen/arch/arm/domain_build.c                   |  66 ++++++
> xen/arch/arm/include/asm/arm64/sve.h          |  72 +++++++
> xen/arch/arm/include/asm/arm64/sysregs.h      |   4 +
> xen/arch/arm/include/asm/arm64/vfp.h          |  12 ++
> xen/arch/arm/include/asm/cpufeature.h         |  14 ++
> xen/arch/arm/include/asm/domain.h             |   8 +
> xen/arch/arm/include/asm/processor.h          |   3 +
> xen/arch/arm/setup.c                          |   5 +-
> xen/arch/arm/sysctl.c                         |   4 +
> xen/arch/arm/traps.c                          |  36 +++-
> xen/arch/x86/dom0_build.c                     |  48 ++---
> xen/common/domain.c                           |  23 +++
> xen/common/kernel.c                           |  28 +++
> xen/include/public/arch-arm.h                 |   2 +
> xen/include/public/sysctl.h                   |   4 +
> xen/include/xen/domain.h                      |   1 +
> xen/include/xen/lib.h                         |  10 +
> 48 files changed, 1052 insertions(+), 107 deletions(-)
> create mode 100644 tools/include/xen-tools/arm-arch-capabilities.h
> create mode 100644 xen/arch/arm/arm64/sve-asm.S
> create mode 100644 xen/arch/arm/arm64/sve.c
> create mode 100644 xen/arch/arm/include/asm/arm64/sve.h

Hi All,

I received some r-by for this serie dependent on some fix, so I will wait until 
next
week for further comments and then I will push the series with the fixes and 
with
the tags to ease the committers work


> 
> -- 
> 2.34.1
> 
>