[PATCH] fix CPUID handling

Alexander Graf
2008-02-25T17:37:19Z

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So this is a new version of the same patch. It should be rather safe
now, as most cases are handled by gcc.

Signed-off-by: Alexander Graf <alex@csgraf.de>

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diff --git a/qemu/qemu-kvm-x86.c b/qemu/qemu-kvm-x86.c
index 37354fb..3062d1b 100644
--- a/qemu/qemu-kvm-x86.c
+++ b/qemu/qemu-kvm-x86.c
@@ -427,36 +427,22 @@ static void host_cpuid(uint32_t function, uint32_t *eax, uint32_t *ebx,
{
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"
+#if defined(__i386__) && defined(__PIC__)
+ /* We need to handle ebx manually, as PIC code requires it */
+ asm volatile("movl %%ebx, %%esi \n\t"
+ "cpuid \n\t"
+ "movl %%ebx, %1 \n\t"
+ "movl %%esi, %%ebx"
+ : "=a" (vec[0]), "=r" (vec[1]), "=c" (vec[2]), "=d" (vec[3])
+ : "0"(function)
+ : "esi", "cc");
#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"
+ asm volatile("cpuid"
+ : "=a" (vec[0]), "=b" (vec[1]),"=c" (vec[2]), "=d" (vec[3])
+ : "0"(function)
+ : "cc");
#endif
- : : "rm"(vec) : "memory");
+
if (eax)
*eax = vec[0];
if (ebx)

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