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Re: [PATCH] x86/CPU: convert vendor hook invocations to altcall
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 16 Jan 2024 09:55:37 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Tue, 16 Jan 2024 08:55:49 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16.01.2024 09:41, Jan Beulich wrote:
> While not performance critical, these hook invocations still want
> converting: This way all pre-filled struct cpu_dev instances can become
> __initconst_cf_clobber, thus allowing to eliminate further 8 ENDBR
> during the 2nd phase of alternatives patching (besides moving previously
> resident data to .init.*).
>
> Since all use sites need touching anyway, take the opportunity and also
> address a Misra C:2012 Rule 5.5 violation: Rename the this_cpu static
> variable.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> With LTO it might end up necessary to tag as __used more than just
> "default_cpu".
Yet then ...
> --- a/xen/arch/x86/cpu/common.c
> +++ b/xen/arch/x86/cpu/common.c
> @@ -113,10 +113,10 @@ static void cf_check default_init(struct
> __clear_bit(X86_FEATURE_SEP, c->x86_capability);
> }
>
> -static const struct cpu_dev default_cpu = {
> +static const struct cpu_dev __initconst_cf_clobber default_cpu = {
... I sent a stale patch, where __used was still missing here.
Considering the intention behind __initconst_cf_clobber I wonder
whether we wouldn't better integrate __used into that macro, such
that we become independent of optimizations the tool chain may be
doing.
Jan
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