On (Wed) Feb 18 2009 [13:21:26], Amit Shah wrote:
> On (Tue) Feb 17 2009 [12:47:10], Brian Kress wrote:
> > When I try to run KVM built off the current head, it crashes with a
> > Segmentation fault. KVM-84 does
> > not. Seems to be dealing with the CPUID changes:
> >
> >
> > 0x081a5c70 in host_cpuid ()
> > at /home/kressb/kvm/src/qemu/target-i386/helper.c:1426
> > 1426 asm volatile("pusha \n\t"
>
> This looks like some kind of stack corruption on 32-bit:
>
> 1472 if (kvm_enabled())
> (gdb)
> 1473 host_cpuid(0, 0, NULL, ebx, ecx, edx);
> (gdb)
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x081a2d60 in host_cpuid (function=10, count=1231384169, eax=0x0,
> ebx=0xadfc1914,
> ecx=0xadfc1910, edx=0xadfc190c)
> at /home/amit/src/kvm-userspace/qemu/target-i386/helper.c:1426
> 1426 asm volatile("pusha \n\t"
>
> I don't see this on 64-bit. Investigating.
Avi, what's the reason for doing this in the host_cpuid code? As I see
it, the first version should work for both 64-bit and 32-bit code.
#ifdef __x86_64__
asm volatile("cpuid"
: "=a"(vec[0]), "=b"(vec[1]),
"=c"(vec[2]), "=d"(vec[3])
: "0"(function), "c"(count) : "cc");
#else
asm volatile("pusha \n\t"
"cpuid \n\t"
"mov %%eax, 0(%1) \n\t"
"mov %%ebx, 4(%1) \n\t"
"mov %%ecx, 8(%1) \n\t"
"mov %%edx, 12(%1) \n\t"
"popa"
: : "a"(function), "c"(count), "S"(vec)
: "memory", "cc");
#endif
Amit
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