Re: [Qemu-devel] [PATCH v4 2/5] x86: Allow physical address bits to be set

[Richard Henderson]

On 07/08/2016 04:36 PM, Eduardo Habkost wrote:
>   -#elif defined(TARGET_X86_64)
>   -#define TARGET_PHYS_ADDR_SPACE_BITS 42
>   -#elif defined(TARGET_I386)
>   -#define TARGET_PHYS_ADDR_SPACE_BITS 36
> [...]
>   --- a/target-i386/cpu.h
>   +++ b/target-i386/cpu.h
> [...]
>   +#ifdef TARGET_X86_64
>   +#define TARGET_PHYS_ADDR_SPACE_BITS 52
>   +/* ??? This is really 48 bits, sign-extended, but the only thing
>   +   accessible to userland with bit 48 set is the VSYSCALL, and that
>   +   is handled via other mechanisms.  */
>   +#define TARGET_VIRT_ADDR_SPACE_BITS 47
>   +#else
>   +#define TARGET_PHYS_ADDR_SPACE_BITS 36
>   +#define TARGET_VIRT_ADDR_SPACE_BITS 32
>   +#endif
>   +
>
> But I really don't understand why it was changed to 52 when the
> macros were moved. A (fortunate) typo?

It was 6 years ago, but I assume that I looked up 52 as a theoretical maximum. 
I'm not going to look it up again to verify though.


r~