linux-kernel - Re: [PATCH] KVM: Move binary stats helpers to header to effectively export them

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Date:   Wed, 11 Aug 2021 10:55:05 -0700
From:   Jing Zhang <jingzhangos@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, KVM <kvm@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: Move binary stats helpers to header to effectively
 export them

On Wed, Aug 11, 2021 at 9:53 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Move kvm_stats_linear_hist_update() and kvm_stats_log_hist_update() to
> kvm_host.h as static inline helpers to resolve a linker error on PPC,
> which references the latter from module code.  This also fixes a goof
> where the functions are tagged as "inline", despite being externs and
> thus not inline-friendy.
>
>   ERROR: modpost: ".kvm_stats_log_hist_update" [arch/powerpc/kvm/kvm-hv.ko] undefined!
>
> Fixes: c8ba95948182 ("KVM: stats: Support linear and logarithmic histogram statistics")
> Cc: Jing Zhang <jingzhangos@...gle.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  include/linux/kvm_host.h | 38 +++++++++++++++++++++++++++++++++++---
>  virt/kvm/binary_stats.c  | 34 ----------------------------------
>  2 files changed, 35 insertions(+), 37 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index d447b21cdd73..e4d712e9f760 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1467,9 +1467,41 @@ ssize_t kvm_stats_read(char *id, const struct kvm_stats_header *header,
>                        const struct _kvm_stats_desc *desc,
>                        void *stats, size_t size_stats,
>                        char __user *user_buffer, size_t size, loff_t *offset);
> -inline void kvm_stats_linear_hist_update(u64 *data, size_t size,
> -                                 u64 value, size_t bucket_size);
> -inline void kvm_stats_log_hist_update(u64 *data, size_t size, u64 value);
> +
> +/**
> + * kvm_stats_linear_hist_update() - Update bucket value for linear histogram
> + * statistics data.
> + *
> + * @data: start address of the stats data
> + * @size: the number of bucket of the stats data
> + * @value: the new value used to update the linear histogram's bucket
> + * @bucket_size: the size (width) of a bucket
> + */
> +static inline void kvm_stats_linear_hist_update(u64 *data, size_t size,
> +                                               u64 value, size_t bucket_size)
> +{
> +       size_t index = div64_u64(value, bucket_size);
> +
> +       index = min(index, size - 1);
> +       ++data[index];
> +}
> +
> +/**
> + * kvm_stats_log_hist_update() - Update bucket value for logarithmic histogram
> + * statistics data.
> + *
> + * @data: start address of the stats data
> + * @size: the number of bucket of the stats data
> + * @value: the new value used to update the logarithmic histogram's bucket
> + */
> +static inline void kvm_stats_log_hist_update(u64 *data, size_t size, u64 value)
> +{
> +       size_t index = fls64(value);
> +
> +       index = min(index, size - 1);
> +       ++data[index];
> +}
> +
>  #define KVM_STATS_LINEAR_HIST_UPDATE(array, value, bsize)                     \
>         kvm_stats_linear_hist_update(array, ARRAY_SIZE(array), value, bsize)
>  #define KVM_STATS_LOG_HIST_UPDATE(array, value)                                       \
> diff --git a/virt/kvm/binary_stats.c b/virt/kvm/binary_stats.c
> index 9bd595c92d3a..eefca6c69f51 100644
> --- a/virt/kvm/binary_stats.c
> +++ b/virt/kvm/binary_stats.c
> @@ -142,37 +142,3 @@ ssize_t kvm_stats_read(char *id, const struct kvm_stats_header *header,
>         *offset = pos;
>         return len;
>  }
> -
> -/**
> - * kvm_stats_linear_hist_update() - Update bucket value for linear histogram
> - * statistics data.
> - *
> - * @data: start address of the stats data
> - * @size: the number of bucket of the stats data
> - * @value: the new value used to update the linear histogram's bucket
> - * @bucket_size: the size (width) of a bucket
> - */
> -inline void kvm_stats_linear_hist_update(u64 *data, size_t size,
> -                                 u64 value, size_t bucket_size)
> -{
> -       size_t index = div64_u64(value, bucket_size);
> -
> -       index = min(index, size - 1);
> -       ++data[index];
> -}
> -
> -/**
> - * kvm_stats_log_hist_update() - Update bucket value for logarithmic histogram
> - * statistics data.
> - *
> - * @data: start address of the stats data
> - * @size: the number of bucket of the stats data
> - * @value: the new value used to update the logarithmic histogram's bucket
> - */
> -inline void kvm_stats_log_hist_update(u64 *data, size_t size, u64 value)
> -{
> -       size_t index = fls64(value);
> -
> -       index = min(index, size - 1);
> -       ++data[index];
> -}
> --
> 2.32.0.605.g8dce9f2422-goog
>
Thanks for fixing it, Sean!

Reviewed-by: Jing Zhang <jingzhangos@...gle.com>