[Xen-devel] Re: [RFC PATCH 19/35] subarch support for control register accesses

[Zachary Amsden <zach@xxxxxxxxxx>]

Chris Wright wrote:
> +#define read_cr4_safe() ({                           \
> +       unsigned int __dummy;                         \
> +       /* This could fault if %cr4 does not exist */ \
> +       __asm__("1: movl %%cr4, %0         \n"   \
> +               "2:                                \n"   \
> +               ".section __ex_table,\"a\"       \n"   \
> +               ".long 1b,2b                       \n"   \
> +               ".previous                 \n"   \
> +               : "=r" (__dummy): "0" (0));       \
> +       __dummy;                                      \
> +})
I think you'll find trap and emulate quite sufficient for this one.

> +#define stts() write_cr0(8 | read_cr0())
>   
Nit: You shouldn't need to redefine stts() in the subarch.

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