Re: [PATCH v2 3/3] KVM: s390: Increase size of union sca_utility to four bytes
From: Claudio Imbrenda
Date: Tue Nov 26 2024 - 07:22:24 EST
On Tue, 26 Nov 2024 13:09:56 +0100
Janosch Frank <frankja@xxxxxxxxxxxxx> wrote:
> On 11/26/24 11:25 AM, Heiko Carstens wrote:
> [...]
> > union sca_utility {
>
> Would you mind adding a comment?
>
>
> ""Utility is defined as 2 bytes but having it 4 bytes wide generates
> more efficient code. Since the following bytes are reserved this makes
> no functional difference.""
looks good, thanks!
>
> > - __u16 val;
> > + __u32 val;
> > struct {
> > - __u16 mtcr : 1;
> > - __u16 reserved : 15;
> > + __u32 mtcr : 1;
> > + __u32 : 31;
> > };
> > };
> >
> > @@ -107,7 +107,7 @@ struct bsca_block {
> > __u64 reserved[5];
> > __u64 mcn;
> > union sca_utility utility;
> > - __u8 reserved2[6];
> > + __u8 reserved2[4];
> > struct bsca_entry cpu[KVM_S390_BSCA_CPU_SLOTS];
> > };
> >
> > @@ -115,7 +115,7 @@ struct esca_block {
> > union ipte_control ipte_control;
> > __u64 reserved1[6];
> > union sca_utility utility;
> > - __u8 reserved2[6];
> > + __u8 reserved2[4];
> > __u64 mcn[4];
> > __u64 reserved3[20];
> > struct esca_entry cpu[KVM_S390_ESCA_CPU_SLOTS];
>