Avi Kivity wrote:
On 03/31/2011 03:13 PM, Andre Przywara wrote:If KVM cannot find an exact match for a requested CPUID leaf, the code will try to find the closest match instead of simply confessing it's failure. The implementation was meant to satisfy the CPUID specification, but did not properly check for extended and standard leaves and also didn't account for the index subleaf. Beside that this rule only applies to CPUID intercepts, which is not the only user of the kvm_find_cpuid_entry() function. So fix this algorithm and move it into kvm_emulate_cpuid(). This fixes a crash of newer Linux kernels as KVM guests on AMD Bulldozer CPUs, where bogus values were returned in response to a CPUID intercept. @@ -4996,6 +4990,19 @@ void kvm_emulate_cpuid(struct kvm_vcpu *vcpu) kvm_register_write(vcpu, VCPU_REGS_RCX, 0); kvm_register_write(vcpu, VCPU_REGS_RDX, 0); best = kvm_find_cpuid_entry(vcpu, function, index); + + /* if no match is found, check whether we exceed the vCPU's limit + * and return the content of the highest valid standard leaf instead. + * This is to satisfy the CPUID specification. + */ + if (!best) { + best = kvm_find_cpuid_entry(vcpu, function& 0x80000000, 0);"highest valid standard leaf" means the second argument should be zero, no?
Weird, but somehow true. I fixed this is in a another version (following). Thanks for spotting this. Andre.
+ if (best&& best->eax< function) + best = kvm_find_cpuid_entry(vcpu, best->eax, index); + else + best = NULL; + } + if (best) { kvm_register_write(vcpu, VCPU_REGS_RAX, best->eax); kvm_register_write(vcpu, VCPU_REGS_RBX, best->ebx);
-- Andre Przywara AMD-Operating System Research Center (OSRC), Dresden, Germany -- 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
