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authorAndre Przywara <andre.przywara@amd.com>2011-03-31 10:58:49 -0400
committerAvi Kivity <avi@redhat.com>2011-04-06 06:15:56 -0400
commitbd22f5cfcfe8f68bf43b72daf4530cd7eedc9b7a (patch)
tree8f479fb862bd422e7cdbe8b240e1fdd4978f725b /arch
parent20800bc940af671257abc97ad362abe3c21ddd50 (diff)
KVM: move and fix substitue search for missing CPUID entries
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 call it from 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. Signed-off-by: Andre Przywara <andre.przywara@amd.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c31
1 files changed, 25 insertions, 6 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4a1ba05f7af3..934b4c6b0bf9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4958,12 +4958,6 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
4958 best = e; 4958 best = e;
4959 break; 4959 break;
4960 } 4960 }
4961 /*
4962 * Both basic or both extended?
4963 */
4964 if (((e->function ^ function) & 0x80000000) == 0)
4965 if (!best || e->function > best->function)
4966 best = e;
4967 } 4961 }
4968 return best; 4962 return best;
4969} 4963}
@@ -4983,6 +4977,27 @@ not_found:
4983 return 36; 4977 return 36;
4984} 4978}
4985 4979
4980/*
4981 * If no match is found, check whether we exceed the vCPU's limit
4982 * and return the content of the highest valid _standard_ leaf instead.
4983 * This is to satisfy the CPUID specification.
4984 */
4985static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
4986 u32 function, u32 index)
4987{
4988 struct kvm_cpuid_entry2 *maxlevel;
4989
4990 maxlevel = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0);
4991 if (!maxlevel || maxlevel->eax >= function)
4992 return NULL;
4993 if (function & 0x80000000) {
4994 maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0);
4995 if (!maxlevel)
4996 return NULL;
4997 }
4998 return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
4999}
5000
4986void kvm_emulate_cpuid(struct kvm_vcpu *vcpu) 5001void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
4987{ 5002{
4988 u32 function, index; 5003 u32 function, index;
@@ -4995,6 +5010,10 @@ void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
4995 kvm_register_write(vcpu, VCPU_REGS_RCX, 0); 5010 kvm_register_write(vcpu, VCPU_REGS_RCX, 0);
4996 kvm_register_write(vcpu, VCPU_REGS_RDX, 0); 5011 kvm_register_write(vcpu, VCPU_REGS_RDX, 0);
4997 best = kvm_find_cpuid_entry(vcpu, function, index); 5012 best = kvm_find_cpuid_entry(vcpu, function, index);
5013
5014 if (!best)
5015 best = check_cpuid_limit(vcpu, function, index);
5016
4998 if (best) { 5017 if (best) {
4999 kvm_register_write(vcpu, VCPU_REGS_RAX, best->eax); 5018 kvm_register_write(vcpu, VCPU_REGS_RAX, best->eax);
5000 kvm_register_write(vcpu, VCPU_REGS_RBX, best->ebx); 5019 kvm_register_write(vcpu, VCPU_REGS_RBX, best->ebx);