Messages in this thread | | | Date | Wed, 18 Jul 2007 18:20:35 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] i386: Decouple PAE from CONFIG_CMPXCHG64 |
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Andi Kleen wrote: >> >> No processors that support KVM exist that also do not support CMPXCHG64, >> so no additional check is necessary. This setup allows for a single kernel >> that will boot on i486 and also support KVM if available. > > The CONFIG should only control the early CPUID checks, which are needed for PAE > kernels. > > But for something late like KVM the correct fix is really to drop > the ifdefs around the macro and check boot_cpu_has() yourself. >
He's checking for the appropriate functionality at runtime. What this does is makes it impossible to select KVM when you have already selected a CPU that doesn't support CX8.
One can, of course, question the utility, since the CPU set that supports KVM all support CX8, but not vice versa...
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