[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] [BUG] x86-64 floating point environment handling
On 28 Nov 2005, at 15:35, Jan Beulich wrote:
Besides the minor problem of the save/restore code needlessly beingconditional for x86-64 (cpu_has_fxsr should always be set for all 64-bitCPUs) there is a more significant problem: Both FXSAVE and FXRSTOR require, for a 64-bit environment, 64-bit operand size to be explicitly used. Simply adding a rex64/ prefix, however, doesn't work because
The only difference between rex64-prefixed fxsave and non-prefixed fxsave is the format of the last-instruction/data pointers. Does anyone make use of those? I notice that Linux always uses the rex64-prefixed version of fxsave, so I guess not (at least, not in 32-bit apps running on 64-bit linux).
It's very unlikely we'd implement expensive and complicated logic in Xen to ensure consistency of FP state that noone uses.
-- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
Lists.xenproject.org is hosted with RackSpace, monitoring our