Re: [PATCH v2 0/9] i386/cpu: Support APX for KVM

[Paolo Bonzini <pbonzini@redhat.com>]

On 12/11/25 08:09, Zhao Liu wrote:
> Hi,
> 
> This series adds APX (Advanced Performance Extensions) support in QEMU
> to enable APX in Guest based on KVM (RFC v1 [1]).
> 
> This series is based on CET v5:
> 
> https://lore.kernel.org/qemu-devel/20251211060801.3600039-1-zhao1.liu@intel.com/
> 
> And you can also find the code here:
> 
> https://gitlab.com/zhao.liu/qemu/-/commits/i386-all-for-dmr-v2.1-12-10-2025
> 
> Compared with v1 [2], v2 adds:
>   * HMP support ("print" & "info registers").
>   * gdbstub support.
> 
> Thanks for your review!

Great, thanks!  Just one question, should the CPUID feature be "apx" or 
"apxf" (and therefore CPUID_7_1_EDX_APXF)?  I can fix that myself of course.

Thanks,

Paolo

> 
> Overview
> ========
> 
> Intel Advanced Performance Extensions (Intel APX) expands the Intel 64
> instruction set architecture with access to more registers (16
> additional general-purpose registers (GPRs) R16–R31) and adds various
> new features that improve general-purpose performance. The extensions
> are designed to provide efficient performance gains across a variety of
> workloads without significantly increasing silicon area or power
> consumption of the core.
> 
> APX spec link (rev.07) is:
> https://cdrdv2.intel.com/v1/dl/getContent/861610
> 
> At QEMU side, the enabling work mainly includes three parts:
> 
> 1. save/restore/migrate the xstate of APX.
>     * APX xstate is a user xstate, but it reuses MPX xstate area in
>       un-compacted XSAVE buffer.
>     * To address this, QEMU will reject both APX and MPX if their CPUID
>       feature bits are set at the same (in Patch 1).
> 
> 2. add related CPUIDs support in feature words.
> 
> 3. debug support, including HMP & gdbstub.
> 
> 
> Change Log
> ==========
> 
> Changes sicne v1:
>   * Expend current GPR array (CPUX86State.regs) to 32 elements instead of
>     a new array.
>   * HMP support ("print" & "info registers").
>   * gdbstub support.
> 
> [1]: KVM RFC: https://lore.kernel.org/kvm/20251110180131.28264-1-chang.seok.bae@intel.com/
> [2]: QEMU APX v1: https://lore.kernel.org/qemu-devel/20251118065817.835017-1-zhao1.liu@intel.com/
> 
> Thanks and Best Regards,
> Zhao
> ---
> Zhao Liu (6):
>    i386/machine: Use VMSTATE_UINTTL_SUB_ARRAY for vmstate of
>      CPUX86State.regs
>    i386/gdbstub: Add APX support for gdbstub
>    i386/cpu-dump: Dump entended GPRs for APX supported guest
>    i386/monitor: Support EGPRs in hmp_print
>    i386/cpu: Support APX CPUIDs
>    i386/cpu: Mark APX xstate as migratable
> 
> Zide Chen (3):
>    i386/cpu: Add APX EGPRs into xsave area
>    i386/cpu: Cache EGPRs in CPUX86State
>    i386/cpu: Add APX migration support
> 
>   configs/targets/x86_64-softmmu.mak |  2 +-
>   gdb-xml/i386-64bit-apx.xml         | 26 +++++++++++
>   include/migration/cpu.h            |  4 ++
>   target/i386/cpu-dump.c             | 30 +++++++++++--
>   target/i386/cpu.c                  | 68 ++++++++++++++++++++++++++++-
>   target/i386/cpu.h                  | 48 +++++++++++++++++++--
>   target/i386/gdbstub.c              | 69 +++++++++++++++++++++++++++++-
>   target/i386/machine.c              | 27 +++++++++++-
>   target/i386/monitor.c              | 16 +++++++
>   target/i386/xsave_helper.c         | 16 +++++++
>   10 files changed, 293 insertions(+), 13 deletions(-)
>   create mode 100644 gdb-xml/i386-64bit-apx.xml
>