[SeaBIOS] [PATCH] smm: ignore bits 16,18-31 of SMM revision ID

[Kevin O'Connor]

On Wed, May 06, 2015 at 12:38:29PM +0200, Paolo Bonzini wrote:
> Bits 16-31 of the SMM revision ID are feature bits.  We only need to
> check that SMBASE relocation is supported, but do not care about other
> features.  In particular, this allows the SMM I/O instruction restart
> feature to be present.
> 
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> ---
>  src/fw/smm.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/src/fw/smm.c b/src/fw/smm.c
> index dabc677..6cb484e 100644
> --- a/src/fw/smm.c
> +++ b/src/fw/smm.c
> @@ -18,8 +18,14 @@
>  #include "util.h" // smm_setup
>  #include "x86.h" // wbinvd
>  
> -#define SMM_REV_I32 0x00020000
> -#define SMM_REV_I64 0x00020064
> +/*
> + * Check SMM state save area format (bits 0-15) and require support
> + * for SMBASE relocation.
> + */
> +#define SMM_REV_MASK 0x0002ffff
> +
> +#define SMM_REV_I32  0x00020000
> +#define SMM_REV_I64  0x00020064
>  
>  struct smm_state {
>      union {
> @@ -62,9 +68,10 @@ handle_smi(u16 cs)
>  
>      if (smm == (void*)BUILD_SMM_INIT_ADDR) {
>          // relocate SMBASE to 0xa0000
> -        if (smm->cpu.i32.smm_rev == SMM_REV_I32) {
> +        u32 rev = smm->cpu.i32.smm_rev & SMM_REV_MASK;
> +        if (rev == SMM_REV_I32) {

I noticed that this patch from May changes the revision check to use a
mask in the SMM init code, but doesn't change the check in the runtime
part of the handler.  Was this intentional?

-Kevin