On Wed, Nov 06, 2013 at 10:35:27PM +0100, Stefan Weil wrote:
> This error was reported by valgrind when running qemu-system-x86_64
> with kvm:
>
> ==975== Conditional jump or move depends on uninitialised value(s)
> ==975== at 0x521C38: cpuid_find_entry (kvm.c:176)
> ==975== by 0x5235BA: kvm_arch_init_vcpu (kvm.c:686)
> ==975== by 0x4D5175: kvm_init_vcpu (kvm-all.c:267)
> ==975== by 0x45035B: qemu_kvm_cpu_thread_fn (cpus.c:858)
> ==975== by 0xD361E0D: start_thread (pthread_create.c:311)
> ==975== by 0xD65E9EC: clone (clone.S:113)
> ==975== Uninitialised value was created by a stack allocation
> ==975== at 0x5226E4: kvm_arch_init_vcpu (kvm.c:446)
>
> Instead of adding more memset calls for parts of cpuid_data, the existing
> calls were removed and cpuid_data is now initialized completely in one
> call.
>
> Signed-off-by: Stefan Weil <sw@xxxxxxxxxxx>
Applied, thanks.
> ---
>
> I did not check whether older versions also need this fix.
>
> Stefan W.
>
> target-i386/kvm.c | 9 ++-------
> 1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 749aa09..3ffd3e0 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -456,11 +456,12 @@ int kvm_arch_init_vcpu(CPUState *cs)
> uint32_t signature[3];
> int r;
>
> + memset(&cpuid_data, 0, sizeof(cpuid_data));
> +
> cpuid_i = 0;
>
> /* Paravirtualization CPUIDs */
> c = &cpuid_data.entries[cpuid_i++];
> - memset(c, 0, sizeof(*c));
> c->function = KVM_CPUID_SIGNATURE;
> if (!hyperv_enabled(cpu)) {
> memcpy(signature, "KVMKVMKVM\0\0\0", 12);
> @@ -474,7 +475,6 @@ int kvm_arch_init_vcpu(CPUState *cs)
> c->edx = signature[2];
>
> c = &cpuid_data.entries[cpuid_i++];
> - memset(c, 0, sizeof(*c));
> c->function = KVM_CPUID_FEATURES;
> c->eax = env->features[FEAT_KVM];
>
> @@ -483,13 +483,11 @@ int kvm_arch_init_vcpu(CPUState *cs)
> c->eax = signature[0];
>
> c = &cpuid_data.entries[cpuid_i++];
> - memset(c, 0, sizeof(*c));
> c->function = HYPERV_CPUID_VERSION;
> c->eax = 0x00001bbc;
> c->ebx = 0x00060001;
>
> c = &cpuid_data.entries[cpuid_i++];
> - memset(c, 0, sizeof(*c));
> c->function = HYPERV_CPUID_FEATURES;
> if (cpu->hyperv_relaxed_timing) {
> c->eax |= HV_X64_MSR_HYPERCALL_AVAILABLE;
> @@ -500,7 +498,6 @@ int kvm_arch_init_vcpu(CPUState *cs)
> }
>
> c = &cpuid_data.entries[cpuid_i++];
> - memset(c, 0, sizeof(*c));
> c->function = HYPERV_CPUID_ENLIGHTMENT_INFO;
> if (cpu->hyperv_relaxed_timing) {
> c->eax |= HV_X64_RELAXED_TIMING_RECOMMENDED;
> @@ -511,13 +508,11 @@ int kvm_arch_init_vcpu(CPUState *cs)
> c->ebx = cpu->hyperv_spinlock_attempts;
>
> c = &cpuid_data.entries[cpuid_i++];
> - memset(c, 0, sizeof(*c));
> c->function = HYPERV_CPUID_IMPLEMENT_LIMITS;
> c->eax = 0x40;
> c->ebx = 0x40;
>
> c = &cpuid_data.entries[cpuid_i++];
> - memset(c, 0, sizeof(*c));
> c->function = KVM_CPUID_SIGNATURE_NEXT;
> memcpy(signature, "KVMKVMKVM\0\0\0", 12);
> c->eax = 0;
> --
> 1.7.10.4
--
Gleb.
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