Re: [Xen-devel] [PATCH 3/3] x86/HVM: prefer structure assignment for seg reg copying

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 06 December 2016 11:45
> To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>; Andrew
> Cooper <Andrew.Cooper3@xxxxxxxxxx>; Paul Durrant
> <Paul.Durrant@xxxxxxxxxx>; George Dunlap <George.Dunlap@xxxxxxxxxx>;
> Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Subject: [PATCH 3/3] x86/HVM: prefer structure assignment for seg reg
> copying
> 
> This makes things type safe.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> 
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1434,7 +1434,8 @@ static int hvmemul_read_segment(
>      if ( IS_ERR(sreg) )
>           return -PTR_ERR(sreg);
> 
> -    memcpy(reg, sreg, sizeof(struct segment_register));
> +    *reg = *sreg;
> +
>      return X86EMUL_OKAY;
>  }
> 
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -654,39 +654,39 @@ static void svm_get_segment_register(str
>      switch ( seg )
>      {
>      case x86_seg_cs:
> -        memcpy(reg, &vmcb->cs, sizeof(*reg));
> +        *reg = vmcb->cs;
>          break;
>      case x86_seg_ds:
> -        memcpy(reg, &vmcb->ds, sizeof(*reg));
> +        *reg = vmcb->ds;
>          break;
>      case x86_seg_es:
> -        memcpy(reg, &vmcb->es, sizeof(*reg));
> +        *reg = vmcb->es;
>          break;
>      case x86_seg_fs:
>          svm_sync_vmcb(v);
> -        memcpy(reg, &vmcb->fs, sizeof(*reg));
> +        *reg = vmcb->fs;
>          break;
>      case x86_seg_gs:
>          svm_sync_vmcb(v);
> -        memcpy(reg, &vmcb->gs, sizeof(*reg));
> +        *reg = vmcb->gs;
>          break;
>      case x86_seg_ss:
> -        memcpy(reg, &vmcb->ss, sizeof(*reg));
> +        *reg = vmcb->ss;
>          reg->attr.fields.dpl = vmcb->_cpl;
>          break;
>      case x86_seg_tr:
>          svm_sync_vmcb(v);
> -        memcpy(reg, &vmcb->tr, sizeof(*reg));
> +        *reg = vmcb->tr;
>          break;
>      case x86_seg_gdtr:
> -        memcpy(reg, &vmcb->gdtr, sizeof(*reg));
> +        *reg = vmcb->gdtr;
>          break;
>      case x86_seg_idtr:
> -        memcpy(reg, &vmcb->idtr, sizeof(*reg));
> +        *reg = vmcb->idtr;
>          break;
>      case x86_seg_ldtr:
>          svm_sync_vmcb(v);
> -        memcpy(reg, &vmcb->ldtr, sizeof(*reg));
> +        *reg = vmcb->ldtr;
>          break;
>      default:
>          BUG();
> @@ -729,26 +729,26 @@ static void svm_set_segment_register(str
>      switch ( seg )
>      {
>      case x86_seg_cs:
> -        memcpy(&vmcb->cs, reg, sizeof(*reg));
> +        vmcb->cs = *reg;
>          break;
>      case x86_seg_ds:
> -        memcpy(&vmcb->ds, reg, sizeof(*reg));
> +        vmcb->ds = *reg;
>          break;
>      case x86_seg_es:
> -        memcpy(&vmcb->es, reg, sizeof(*reg));
> +        vmcb->es = *reg;
>          break;
>      case x86_seg_fs:
> -        memcpy(&vmcb->fs, reg, sizeof(*reg));
> +        vmcb->fs = *reg;
>          break;
>      case x86_seg_gs:
> -        memcpy(&vmcb->gs, reg, sizeof(*reg));
> +        vmcb->gs = *reg;
>          break;
>      case x86_seg_ss:
> -        memcpy(&vmcb->ss, reg, sizeof(*reg));
> +        vmcb->ss = *reg;
>          vmcb->_cpl = vmcb->ss.attr.fields.dpl;
>          break;
>      case x86_seg_tr:
> -        memcpy(&vmcb->tr, reg, sizeof(*reg));
> +        vmcb->tr = *reg;
>          break;
>      case x86_seg_gdtr:
>          vmcb->gdtr.base = reg->base;
> @@ -759,7 +759,7 @@ static void svm_set_segment_register(str
>          vmcb->idtr.limit = reg->limit;
>          break;
>      case x86_seg_ldtr:
> -        memcpy(&vmcb->ldtr, reg, sizeof(*reg));
> +        vmcb->ldtr = *reg;
>          break;
>      default:
>          BUG();
> 
> 


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