Re: [PATCH v1 1/1] KVM: s390: Don't cast parameter in bit operations

Claudio Imbrenda
2022-02-24T11:36:40Z

On Wed, 23 Feb 2022 18:44:20 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> While in this particular case it would not be a (critical) issue,
> the pattern itself is bad and error prone in case somebody blindly
> copies to their code.
>
> Don't cast parameter to unsigned long pointer in the bit operations.
> Instead copy to a local variable on stack of a proper type and use.
>
> Fixes: d77e64141e32 ("KVM: s390: implement GISA IPM related primitives")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> arch/s390/include/asm/kvm_host.h | 5 ++++-
> arch/s390/kvm/interrupt.c | 6 +++---
> 2 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index a22c9266ea05..f1c4a1b9b360 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -867,7 +867,10 @@ struct kvm_s390_gisa {
> u8 reserved03[11];
> u32 airq_count;
> } g1;
> - struct {
> + struct { /* as a 256-bit bitmap */
> + DECLARE_BITMAP(b, 256);
> + } bitmap;
> + struct { /* as a set of 64-bit words */
> u64 word[4];
> } u64;
> };
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index db933c252dbc..04e055cbd080 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -304,7 +304,7 @@ static inline int gisa_in_alert_list(struct kvm_s390_gisa *gisa)
>
> static inline void gisa_set_ipm_gisc(struct kvm_s390_gisa *gisa, u32 gisc)
> {
> - set_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa);
> + set_bit_inv(IPM_BIT_OFFSET + gisc, gisa->bitmap.b);

wouldn't it be enough to pass gisa->u64.word here?
then no cast would be necessary

> }
>
> static inline u8 gisa_get_ipm(struct kvm_s390_gisa *gisa)
> @@ -314,12 +314,12 @@ static inline u8 gisa_get_ipm(struct kvm_s390_gisa *gisa)
>
> static inline void gisa_clear_ipm_gisc(struct kvm_s390_gisa *gisa, u32 gisc)
> {
> - clear_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa);
> + clear_bit_inv(IPM_BIT_OFFSET + gisc, gisa->bitmap.b);
> }
>
> static inline int gisa_tac_ipm_gisc(struct kvm_s390_gisa *gisa, u32 gisc)
> {
> - return test_and_clear_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa);
> + return test_and_clear_bit_inv(IPM_BIT_OFFSET + gisc, gisa->bitmap.b);
> }
>
> static inline unsigned long pending_irqs_no_gisa(struct kvm_vcpu *vcpu)