Re: [PATCH] KVM: Avoid using vmx instruction directly

Arnd Bergmann
2006-11-09T14:42:30Z

On Thursday 09 November 2006 14:36, Avi Kivity wrote:
>
> >
> > I'm not an expert on inline assembly, but don't you need an extra
> > '"m" (phys_addr)' to make sure that gcc actually puts the variable
> > on the stack instead of passing a NULL pointer as '"a"(&phys_addr)'?
>
> Taking a variable's address should force its contents into memory (like
> calling an uninlined function with &var).

No it doesn't. You're not telling gcc that the inline assembly cares
about the contents of the variable, so it could be a reference to
a stack slot while the contents are still in a register. Or gcc
might move the assignment of phys_addr to after the inline assembly.

Arnd <><

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