Christian Borntraeger wrote:
Am Donnerstag, 26. Juni 2008 schrieb Avi Kivity:
I don't think "p" should force the contents into memory? Perhaps
"m"(*(char *)buffer)?
Anthony, I don't see why a memory clobber would tell gcc that the
variables is actually used. The problem is with the void * -> unsigned
long cast (__pa), once that happens gcc loses track. It's probably
needed anyway since hypercalls _do_ clobber memory.
I I think about that again, the correct solution should be to use 2 input
constraints for parameters together with the memory clobber on hypercall.
I think something like the following covers all cases:
static inline long kvm_hypercall1(unsigned int nr, unsigned long p1)
{
long ret;
asm volatile(KVM_HYPERCALL
: "=a"(ret)
: "a"(nr), "b"(p1), "m"(*(char *) p1)
: "memory" );
return ret;
}
The address and the memory content of p1 (if it is a pointer) is not ommitted
by gcc. Furthermore, the memory clobbering nature of a hypercall is specified
as well.
That only works if p1 is a virtual address. x86 (and ppc) hypercalls
use physical addresses.
--
error compiling committee.c: too many arguments to function
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