Re: [Qemu-devel] [PATCH 2/9] alpha-linux-user: Work around hosted mmap allocation problems

["Andreas Färber" <afaerber@suse.de>]

Am 08.06.2012 00:24, schrieb Richard Henderson:
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  target-alpha/cpu.h |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/target-alpha/cpu.h b/target-alpha/cpu.h
> index 99f9ee1..0d87fa7 100644
> --- a/target-alpha/cpu.h
> +++ b/target-alpha/cpu.h
> @@ -40,9 +40,20 @@
>  
>  #define TARGET_PAGE_BITS 13
>  
> +#ifdef CONFIG_USER_ONLY
> +/* ??? The kernel likes to give addresses in high memory.  If the host has
> +   more virtual address space than the guest, this can lead to impossible
> +   allocations.  Honor the long-standing assumption that only kernel addrs
> +   are negative, but otherwise allow allocations anywhere.  This could lead
> +   to tricky emulation problems for programs doing tagged addressing, but
> +   that's far fewer than encounter the impossible allocation problem.  */
> +#define TARGET_PHYS_ADDR_SPACE_BITS	63
> +#define TARGET_VIRT_ADDR_SPACE_BITS	63
> +#else
>  /* ??? EV4 has 34 phys addr bits, EV5 has 40, EV6 has 44.  */
>  #define TARGET_PHYS_ADDR_SPACE_BITS	44
>  #define TARGET_VIRT_ADDR_SPACE_BITS	(30 + TARGET_PAGE_BITS)
> +#endif
>  
>  /* Alpha major type */
>  enum {

This looks fishy to me... why should the kernel use a bigger address
space than hardware? For arm on x86_64 such a workaround was not
necessary iirc.

Andreas

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