Re: [Xen-devel] [PATCH] Speed up superpage mapping, take 2

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 25.05.10 at 16:30, Dave McCracken <dcm@xxxxxxxx> wrote:

I didn't look in any great detail at other aspects of the patch, but this

> --- xen-staging/xen/include/public/arch-x86/xen-x86_32.h      2010-05-18 
> 09:45:54.000000000 -0500
> +++ xen-staging-fs//xen/include/public/arch-x86/xen-x86_32.h  2010-05-25 
> 09:19:03.000000000 -0500
> @@ -64,9 +64,9 @@
>  #define FLAT_USER_DS    FLAT_RING3_DS
>  #define FLAT_USER_SS    FLAT_RING3_SS
>  
> -#define __HYPERVISOR_VIRT_START_PAE    0xF5800000
> -#define __MACH2PHYS_VIRT_START_PAE     0xF5800000
> -#define __MACH2PHYS_VIRT_END_PAE       0xF6800000
> +#define __HYPERVISOR_VIRT_START_PAE    0xF5600000
> +#define __MACH2PHYS_VIRT_START_PAE     0xF5600000
> +#define __MACH2PHYS_VIRT_END_PAE       0xF6600000
>  #define HYPERVISOR_VIRT_START_PAE      \
>      mk_unsigned_long(__HYPERVISOR_VIRT_START_PAE)
>  #define MACH2PHYS_VIRT_START_PAE       \

is absolutely forbidden: You cannot lower the start address of
the hypervisor address space hole - no kernel can be expected
to be able to deal with that. I think you will need to make the
feature 64-bit specific, unless you can find a 2Mb range within
the existing hole (but I doubt there is any room left), or unless
you map the table dynamically as needed for 32-bits.

Jan


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