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

Michael Mueller
2022-02-24T12:10:45Z

On 24.02.22 12:36, Claudio Imbrenda wrote:
> 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

we do that at several places

arch/s390/kernel/processor.c: for_each_set_bit_inv(bit, (long
*)&stfle_fac_list, MAX_FACILITY_BIT)
arch/s390/kvm/interrupt.c: set_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned
long *) gisa);
arch/s390/kvm/kvm-s390.c: set_bit_inv(vcpu->vcpu_id, (unsigned long *)
sca->mcn);
arch/s390/kvm/kvm-s390.c: set_bit_inv(vcpu->vcpu_id, (unsigned long *)
&sca->mcn);

>
>> }
>>
>> 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)
>