https://bugzilla.kernel.org/show_bug.cgi?id=77271 Bug ID: 77271 Summary: CPUID Leaf 0x40000000 return 0 in eax Product: Virtualization Version: unspecified Kernel Version: 3.14 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: kvm Assignee: virtualization_kvm@xxxxxxxxxxxxxxxxxxxx Reporter: jidong.xiao@xxxxxxxxx Regression: No I am using kernel 3.14 as the host OS. And using 2.6.34 as the guest OS kernel. According to https://github.com/torvalds/linux/commit/57c22e5f35aa4b9b2fe11f73f3e62bbf9ef36190 Since kernel 3.5, the cpuid instruction (in the Guest OS) with 0x40000000 function should return 0x40000001 in eax, instead of 0. But what I am seeing is, it still returns 0. To reproduce, use a program like this, run it in the Guest: linux:~/code # cat cpusig.c #include <stdio.h> #define cpuid(func,eax,ebx,ecx,edx)\ __asm__ __volatile__ ("cpuid":\ "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (func)); main() { unsigned long a,b,c,d; cpuid(0x40000000,a,b,c,d); printf("0x40000000 KVM_CPUID_SIGNATURE %lx %lx %lx %lx\n",a,b,c,d); } What I saw is: linux:~/code # ./cpusig 0x40000000 KVM_CPUID_SIGNATURE 0 4b4d564b 564b4d56 4d It looks like ebx,ecx,edx all contain right values, but eax does not. -- You are receiving this mail because: You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
