Re: [PATCH v10 7/9] x86emul: support FNSTENV and FNSAVE

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 25/05/2020 15:29, Jan Beulich wrote:
> To avoid introducing another boolean into emulator state, the
> rex_prefix field gets (ab)used to convey the real/VM86 vs protected mode
> info (affecting structure layout, albeit not size) to x86_emul_blk().
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, with one suggestion.

> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -856,6 +856,9 @@ struct x86_emulate_state {
>      enum {
>          blk_NONE,
>          blk_enqcmd,
> +#ifndef X86EMUL_NO_FPU
> +        blk_fst, /* FNSTENV, FNSAVE */
> +#endif
>          blk_movdir,
>      } blk;
>      uint8_t modrm, modrm_mod, modrm_reg, modrm_rm;
> @@ -897,6 +900,50 @@ struct x86_emulate_state {
>  #define PTR_POISON NULL /* 32-bit builds are for user-space, so NULL is OK. 
> */
>  #endif
>  
> +#ifndef X86EMUL_NO_FPU
> +struct x87_env16 {
> +    uint16_t fcw;
> +    uint16_t fsw;
> +    uint16_t ftw;
> +    union {
> +        struct {
> +            uint16_t fip_lo;
> +            uint16_t fop:11, :1, fip_hi:4;
> +            uint16_t fdp_lo;
> +            uint16_t :12, fdp_hi:4;
> +        } real;
> +        struct {
> +            uint16_t fip;
> +            uint16_t fcs;
> +            uint16_t fdp;
> +            uint16_t fds;
> +        } prot;
> +    } mode;
> +};
> +
> +struct x87_env32 {
> +    uint32_t fcw:16, :16;
> +    uint32_t fsw:16, :16;
> +    uint32_t ftw:16, :16;

uint16_t fcw, :16;
uint16_t fsw, :16;
uint16_t ftw, :16;

?

~Andrew