Hi,
I found that on kvm-61 the cpuid in the guest was reported incorrectly
when qemu-kvm was compiled with gcc-4.1 or 4.3.
This resulted in linux-64bit not booting, complaining that it is not
running on a 64-bit machine.
Symptom: Unexpected behaviour after the assembly snippet.
Solution: New assembly which is simpler and leaves optimizations to gcc,
resulting in much shorter and maintainable code.
Comments are welcome,
Bernhard
PS: Thanks a lot to Alex Graf for the fix.
--- qemu/qemu-kvm-x86.c
+++ qemu/qemu-kvm-x86.c
@@ -428,35 +428,7 @@ static void host_cpuid(uint32_t function
uint32_t vec[4];
vec[0] = function;
- asm volatile (
-#ifdef __x86_64__
- "sub $128, %%rsp \n\t" /* skip red zone */
- "push %0; push %%rsi \n\t"
- "push %%rax; push %%rbx; push %%rcx; push %%rdx \n\t"
- "mov 8*5(%%rsp), %%rsi \n\t"
- "mov (%%rsi), %%eax \n\t"
- "cpuid \n\t"
- "mov %%eax, (%%rsi) \n\t"
- "mov %%ebx, 4(%%rsi) \n\t"
- "mov %%ecx, 8(%%rsi) \n\t"
- "mov %%edx, 12(%%rsi) \n\t"
- "pop %%rdx; pop %%rcx; pop %%rbx; pop %%rax \n\t"
- "pop %%rsi; pop %0 \n\t"
- "add $128, %%rsp"
-#else
- "push %0; push %%esi \n\t"
- "push %%eax; push %%ebx; push %%ecx; push %%edx \n\t"
- "mov 4*5(%%esp), %%esi \n\t"
- "mov (%%esi), %%eax \n\t"
- "cpuid \n\t"
- "mov %%eax, (%%esi) \n\t"
- "mov %%ebx, 4(%%esi) \n\t"
- "mov %%ecx, 8(%%esi) \n\t"
- "mov %%edx, 12(%%esi) \n\t"
- "pop %%edx; pop %%ecx; pop %%ebx; pop %%eax \n\t"
- "pop %%esi; pop %0 \n\t"
-#endif
- : : "rm"(vec) : "memory");
+ asm volatile("cpuid" : "+a" (vec[0]), "=b" (vec[1]),"=c" (vec[2]), "=d"
(vec[3]));
if (eax)
*eax = vec[0];
if (ebx)
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