Re: [Xen-devel] [PATCH] hvm/vmx: WRITE_MSR() macro hygene

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Thursday, January 08, 2015 11:39 PM
> 
> Use the standard "do { } while ( 0 )" semantics, and don't hide the break
> statement, incase this macro wants to be used anywhere outside of a switch.
> 
> No functional change, but it is now clear that long_mode_do_msr_write()
> doesn't have fallthough for the STAR, LSTAR and SYSCALL_MASK cases.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> CC: Eddie Dong <eddie.dong@xxxxxxxxx>
> CC: Kevin Tian <kevin.tian@xxxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>

> ---
>  xen/arch/x86/hvm/vmx/vmx.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index f2554d6..522892f 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -152,12 +152,12 @@ void vmx_save_host_msrs(void)
>          rdmsrl(msr_index[i], host_msr_state->msrs[i]);
>  }
> 
> -#define WRITE_MSR(address)
> \
> +#define WRITE_MSR(address) do
> {                                         \
>          guest_msr_state->msrs[VMX_INDEX_MSR_ ## address] =
> msr_content; \
>          set_bit(VMX_INDEX_MSR_ ## address, &guest_msr_state->flags);
> \
>          wrmsrl(MSR_ ## address, msr_content);
> \
>          set_bit(VMX_INDEX_MSR_ ## address, &host_msr_state->flags);
> \
> -        break
> +    } while ( 0 )
> 
>  static enum handler_return
>  long_mode_do_msr_read(unsigned int msr, uint64_t *msr_content)
> @@ -232,11 +232,13 @@ long_mode_do_msr_write(unsigned int msr,
> uint64_t msr_content)
> 
>      case MSR_STAR:
>          WRITE_MSR(STAR);
> +        break;
> 
>      case MSR_LSTAR:
>          if ( !is_canonical_address(msr_content) )
>              goto uncanonical_address;
>          WRITE_MSR(LSTAR);
> +        break;
> 
>      case MSR_CSTAR:
>          if ( !is_canonical_address(msr_content) )
> @@ -246,6 +248,7 @@ long_mode_do_msr_write(unsigned int msr, uint64_t
> msr_content)
> 
>      case MSR_SYSCALL_MASK:
>          WRITE_MSR(SYSCALL_MASK);
> +        break;
> 
>      default:
>          return HNDL_unhandled;
> --
> 1.7.10.4


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