Re: [PATCH 3/8] x86: make TSC usage unconditional

[Brian Gerst]

On Fri, May 22, 2026 at 10:44 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> There are multiple levels of functionality of the TSC that are checked
> for: built into the kernel, present in the CPU, reliable and probably
> more.
>
> Since the TSC-less CPUs are no longer supported in the kernel,
> remove all checks for CONFIG_TSC and X86_FEATURE_TSC and assume
> it's always there. Unfortunately the tsc_clocksource_reliable
> checks are still required though.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  Documentation/virt/kvm/x86/timekeeping.rst |  1 -
>  arch/x86/Kconfig                           |  1 -
>  arch/x86/Kconfig.cpu                       |  1 -
>  arch/x86/events/msr.c                      |  5 ----
>  arch/x86/include/asm/timex.h               |  3 ---
>  arch/x86/include/asm/trace_clock.h         |  8 -------
>  arch/x86/include/asm/tsc.h                 | 13 ----------
>  arch/x86/kernel/Makefile                   |  4 ++--
>  arch/x86/kernel/apic/apic.c                | 23 +++++++-----------
>  arch/x86/kernel/apic/io_apic.c             | 22 +----------------
>  arch/x86/kernel/cpu/centaur.c              |  2 --
>  arch/x86/kernel/cpu/common.c               |  4 +---
>  arch/x86/kernel/cpu/proc.c                 | 15 +++++-------
>  arch/x86/kernel/i8253.c                    |  3 ---
>  arch/x86/kernel/tsc.c                      | 28 ++--------------------
>  arch/x86/lib/kaslr.c                       | 20 ++++------------
>  arch/x86/xen/time.c                        |  2 --
>  drivers/net/ethernet/intel/igc/igc_ptp.c   |  4 ++--
>  drivers/ptp/Kconfig                        |  2 +-
>  tools/power/cpupower/debug/kernel/Makefile |  5 +---
>  20 files changed, 29 insertions(+), 137 deletions(-)
>
> diff --git a/Documentation/virt/kvm/x86/timekeeping.rst b/Documentation/virt/kvm/x86/timekeeping.rst
> index 21ae7efa29ba..e8519451000d 100644
> --- a/Documentation/virt/kvm/x86/timekeeping.rst
> +++ b/Documentation/virt/kvm/x86/timekeeping.rst
> @@ -471,7 +471,6 @@ The following feature bits are used by Linux to signal various TSC attributes,
>  but they can only be taken to be meaningful for UP or single node systems.
>
>  =========================      =======================================
> -X86_FEATURE_TSC                        The TSC is available in hardware
>  X86_FEATURE_RDTSCP             The RDTSCP instruction is available
>  X86_FEATURE_CONSTANT_TSC       The TSC rate is unchanged with P-states
>  X86_FEATURE_NONSTOP_TSC                The TSC does not stop in C-states
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index a188ed90b1ca..2fd99a5b4a68 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -683,7 +683,6 @@ config X86_INTEL_QUARK
>         depends on X86_32
>         depends on X86_EXTENDED_PLATFORM
>         depends on X86_PLATFORM_DEVICES
> -       depends on X86_TSC
>         depends on PCI
>         depends on PCI_GOANY
>         depends on X86_IO_APIC
> diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
> index f4a12b74bed3..fe0246477345 100644
> --- a/arch/x86/Kconfig.cpu
> +++ b/arch/x86/Kconfig.cpu
> @@ -261,7 +261,6 @@ config X86_USE_PPRO_CHECKSUM
>
>  config X86_TSC
>         def_bool y
> -       depends on (MWINCHIP3D || MCRUSOE || MEFFICEON || MCYRIXIII || MK7 || MK6 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || M586MMX || M586TSC || MVIAC3_2 || MVIAC7 || MGEODEGX1 || MGEODE_LX || MATOM) || X86_64

Can't you just delete this config option since it's no longer relevant?