linux-kernel - Re: [PATCH 4/4] x86: switch to cpu_feature_enabled() for X86_FEATURE

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Message-ID: <CAMzpN2hynmZ39ByCRg4ibm=Mz+5LbLps77k9Vhb+c+VmVUO1=A@mail.gmail.com>
Date:   Thu, 3 Nov 2022 09:19:06 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Pu Wen <puwen@...on.cn>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 4/4] x86: switch to cpu_feature_enabled() for X86_FEATURE_XENPV

On Thu, Nov 3, 2022 at 8:37 AM Juergen Gross <jgross@...e.com> wrote:
>
> Convert the remaining cases of static_cpu_has(X86_FEATURE_XENPV) and
> boot_cpu_has(X86_FEATURE_XENPV) to use cpu_feature_enabled(), allowing
> more efficient code in case the kernel is configured without
> CONFIG_XEN_PV.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>  arch/x86/kernel/cpu/amd.c    | 2 +-
>  arch/x86/kernel/cpu/bugs.c   | 2 +-
>  arch/x86/kernel/cpu/hygon.c  | 2 +-
>  arch/x86/kernel/process_64.c | 4 ++--
>  arch/x86/kernel/topology.c   | 2 +-
>  arch/x86/mm/cpu_entry_area.c | 2 +-
>  6 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 860b60273df3..697fe881e967 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -985,7 +985,7 @@ static void init_amd(struct cpuinfo_x86 *c)
>                         set_cpu_cap(c, X86_FEATURE_3DNOWPREFETCH);
>
>         /* AMD CPUs don't reset SS attributes on SYSRET, Xen does. */
> -       if (!cpu_has(c, X86_FEATURE_XENPV))
> +       if (!cpu_feature_enabled(X86_FEATURE_XENPV))
>                 set_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS);
>
>         /*
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index da7c361f47e0..7f78e1527c5e 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -1302,7 +1302,7 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
>                 return SPECTRE_V2_CMD_AUTO;
>         }
>
> -       if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_has(X86_FEATURE_XENPV)) {
> +       if (cmd == SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_FEATURE_XENPV)) {
>                 pr_err("%s selected but running as XenPV guest. Switching to AUTO select\n",
>                        mitigation_options[i].option);
>                 return SPECTRE_V2_CMD_AUTO;
> diff --git a/arch/x86/kernel/cpu/hygon.c b/arch/x86/kernel/cpu/hygon.c
> index 21fd425088fe..1c27645fd429 100644
> --- a/arch/x86/kernel/cpu/hygon.c
> +++ b/arch/x86/kernel/cpu/hygon.c
> @@ -339,7 +339,7 @@ static void init_hygon(struct cpuinfo_x86 *c)
>         set_cpu_cap(c, X86_FEATURE_ARAT);
>
>         /* Hygon CPUs don't reset SS attributes on SYSRET, Xen does. */
> -       if (!cpu_has(c, X86_FEATURE_XENPV))
> +       if (!cpu_feature_enabled(X86_FEATURE_XENPV))
>                 set_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS);
>
>         check_null_seg_clears_base(c);
> diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> index 6b3418bff326..e2f469175be8 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -165,7 +165,7 @@ static noinstr unsigned long __rdgsbase_inactive(void)
>
>         lockdep_assert_irqs_disabled();
>
> -       if (!static_cpu_has(X86_FEATURE_XENPV)) {
> +       if (!cpu_feature_enabled(X86_FEATURE_XENPV)) {
>                 native_swapgs();
>                 gsbase = rdgsbase();
>                 native_swapgs();
> @@ -190,7 +190,7 @@ static noinstr void __wrgsbase_inactive(unsigned long gsbase)
>  {
>         lockdep_assert_irqs_disabled();
>
> -       if (!static_cpu_has(X86_FEATURE_XENPV)) {
> +       if (!cpu_feature_enabled(X86_FEATURE_XENPV)) {
>                 native_swapgs();
>                 wrgsbase(gsbase);
>                 native_swapgs();
> diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
> index 8617d1ed9d31..1b83377274b8 100644
> --- a/arch/x86/kernel/topology.c
> +++ b/arch/x86/kernel/topology.c
> @@ -106,7 +106,7 @@ int arch_register_cpu(int num)
>          * Xen PV guests don't support CPU0 hotplug at all.
>          */
>         if (c->x86_vendor != X86_VENDOR_INTEL ||
> -           boot_cpu_has(X86_FEATURE_XENPV))
> +           cpu_feature_enabled(X86_FEATURE_XENPV))
>                 cpu0_hotpluggable = 0;
>
>         /*
> diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
> index 6c2f1b76a0b6..c83799753d44 100644
> --- a/arch/x86/mm/cpu_entry_area.c
> +++ b/arch/x86/mm/cpu_entry_area.c
> @@ -147,7 +147,7 @@ static void __init setup_cpu_entry_area(unsigned int cpu)
>          * On Xen PV, the GDT must be read-only because the hypervisor
>          * requires it.
>          */
> -       pgprot_t gdt_prot = boot_cpu_has(X86_FEATURE_XENPV) ?
> +       pgprot_t gdt_prot = cpu_feature_enabled(X86_FEATURE_XENPV) ?
>                 PAGE_KERNEL_RO : PAGE_KERNEL;
>         pgprot_t tss_prot = PAGE_KERNEL;
>  #endif

This is another case that can be removed because it's for 32-bit.

--
Brian Gerst