Re: [Qemu-devel] [PATCH 1/3] tcg: add TCG_TARGET_TLB_DISPLACEMENT_BITS

[Richard Henderson <rth@twiddle.net>]

On 02/20/2015 09:57 AM, Paolo Bonzini wrote:
> diff --git a/tcg/i386/tcg-target.h b/tcg/i386/tcg-target.h
> index 7a9980e..8ba977a 100644
> --- a/tcg/i386/tcg-target.h
> +++ b/tcg/i386/tcg-target.h
> @@ -25,6 +25,7 @@
>  #define TCG_TARGET_I386 1
>  
>  #define TCG_TARGET_INSN_UNIT_SIZE  1
> +#define TCG_TARGET_TLB_DISPLACEMENT_BITS 32

31.

Positive displacements only in 64-bit mode.  I don't think it's worth
conditionalizing this for 32-bit, since we can't actually allocate 2G of TLBs
and then actually accomplish anything.  ;-)

> diff --git a/tcg/mips/tcg-target.h b/tcg/mips/tcg-target.h
> index c88a1c9..f5ba52c 100644
> --- a/tcg/mips/tcg-target.h
> +++ b/tcg/mips/tcg-target.h
> @@ -27,6 +27,7 @@
>  #define TCG_TARGET_MIPS 1
>  
>  #define TCG_TARGET_INSN_UNIT_SIZE 4
> +#define TCG_TARGET_TLB_DISPLACEMENT_BITS 16
>  #define TCG_TARGET_NB_REGS 32
>  
>  typedef enum {
> diff --git a/tcg/ppc/tcg-target.h b/tcg/ppc/tcg-target.h
> index 32ac442..7ce7048 100644
> --- a/tcg/ppc/tcg-target.h
> +++ b/tcg/ppc/tcg-target.h
> @@ -32,6 +32,7 @@
>  
>  #define TCG_TARGET_NB_REGS 32
>  #define TCG_TARGET_INSN_UNIT_SIZE 4
> +#define TCG_TARGET_TLB_DISPLACEMENT_BITS 16

Close enough, since the BUILD_BUG_ON should still catch this out if somehow the
size is within that last 16 bytes of 64k.


r~