Ping: [PATCH] x86emul: avoid using _PRE_EFLAGS() in a few cases

[Jan Beulich <jbeulich@xxxxxxxx>]

On 02.06.2021 16:37, Jan Beulich wrote:
> The macro expanding to quite a few insns, replace its use by simply
> clearing the status flags when the to be executed insn doesn't depend
> on their initial state, in cases where this is easily possible. (There
> are more cases where the uses are hidden inside macros, and where some
> of the users of the macros want guest flags put in place before running
> the insn, i.e. the macros can't be updated as easily.)
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Anyone?

Thanks, Jan

> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -6863,7 +6863,8 @@ x86_emulate(
>          }
>          opc[2] = 0xc3;
>  
> -        invoke_stub(_PRE_EFLAGS("[eflags]", "[mask]", "[tmp]"),
> +        _regs.eflags &= ~EFLAGS_MASK;
> +        invoke_stub("",
>                      _POST_EFLAGS("[eflags]", "[mask]", "[tmp]"),
>                      [eflags] "+g" (_regs.eflags),
>                      [tmp] "=&r" (dummy), "+m" (*mmvalp)
> @@ -8111,7 +8112,8 @@ x86_emulate(
>          opc[2] = 0xc3;
>  
>          copy_VEX(opc, vex);
> -        invoke_stub(_PRE_EFLAGS("[eflags]", "[mask]", "[tmp]"),
> +        _regs.eflags &= ~EFLAGS_MASK;
> +        invoke_stub("",
>                      _POST_EFLAGS("[eflags]", "[mask]", "[tmp]"),
>                      [eflags] "+g" (_regs.eflags),
>                      "=a" (dst.val), [tmp] "=&r" (dummy)
> @@ -11698,13 +11700,14 @@ int x86_emul_rmw(
>          break;
>  
>      case rmw_xadd:
> +        *eflags &= ~EFLAGS_MASK;
>          switch ( state->op_bytes )
>          {
>              unsigned long dummy;
>  
>  #define XADD(sz, cst, mod) \
>          case sz: \
> -            asm ( _PRE_EFLAGS("[efl]", "[msk]", "[tmp]") \
> +            asm ( "" \
>                    COND_LOCK(xadd) " %"#mod"[reg], %[mem]; " \
>                    _POST_EFLAGS("[efl]", "[msk]", "[tmp]") \
>                    : [reg] "+" #cst (state->ea.val), \
> 
>