On Fri, Apr 12, 2019 at 05:28:13PM +0100, Dave Martin wrote:
> A complicated DIV_ROUND_UP() expression is currently written out
> explicitly in multiple places in order to specify the size of the
> bitmap exchanged with userspace to represent the value of the
> KVM_REG_ARM64_SVE_VLS pseudo-register.
>
> To make this more readable, this patch replaces these with a single
> define.
>
> Since the number of words in a bitmap is just the index of the last
> word used + 1, this patch expresses the bound that way instead.
> This should make it clearer what is being expressed.
>
> Since use of DIV_ROUND_UP() was the only reason for including
> <linux/kernel.h> in guest.c, this patch removes that #include.
>
> No functional change.
>
> Suggested-by: Andrew Jones <drjones@xxxxxxxxxx>
> Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
> ---
> arch/arm64/kvm/guest.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 73044e3..f025a2f 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -23,7 +23,6 @@
> #include <linux/errno.h>
> #include <linux/err.h>
> #include <linux/nospec.h>
> -#include <linux/kernel.h>
> #include <linux/kvm_host.h>
> #include <linux/module.h>
> #include <linux/stddef.h>
> @@ -209,8 +208,10 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> #define vq_word(vq) (((vq) - SVE_VQ_MIN) / 64)
> #define vq_mask(vq) ((u64)1 << ((vq) - SVE_VQ_MIN) % 64)
>
> +#define SVE_VLS_WORDS (vq_word(SVE_VQ_MAX) + 1)
> +
> static bool vq_present(
> - const u64 (*const vqs)[DIV_ROUND_UP(SVE_VQ_MAX - SVE_VQ_MIN + 1, 64)],
> + const u64 (*const vqs)[SVE_VLS_WORDS],
> unsigned int vq)
> {
> return (*vqs)[vq_word(vq)] & vq_mask(vq);
> @@ -219,7 +220,7 @@ static bool vq_present(
> static int get_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> {
> unsigned int max_vq, vq;
> - u64 vqs[DIV_ROUND_UP(SVE_VQ_MAX - SVE_VQ_MIN + 1, 64)];
> + u64 vqs[SVE_VLS_WORDS];
>
> if (!vcpu_has_sve(vcpu))
> return -ENOENT;
> @@ -243,7 +244,7 @@ static int get_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> static int set_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> {
> unsigned int max_vq, vq;
> - u64 vqs[DIV_ROUND_UP(SVE_VQ_MAX - SVE_VQ_MIN + 1, 64)];
> + u64 vqs[SVE_VLS_WORDS];
>
> if (!vcpu_has_sve(vcpu))
> return -ENOENT;
> --
> 2.1.4
>
This is good, but I wonder if we could define the number of VLS words in
the documentation in terms of SVE_VQ_MAX too. Currently it's just the
hard coded 8 ("__u64 vector_lengths[8]").
Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
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