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

[Chris Wright <chrisw@xxxxxxxxxxxx>]

* Zachary Amsden (zach@xxxxxxxxxx) wrote:
> 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.

Heh ;-)

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

Yes, you're right, better to keep things consolidated.

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