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    Subject[PATCH 1/6] KVM: x86: Fix tracing of CPUID.function when function is out-of-range
    Date
    Rework kvm_cpuid() to query entry->function when adjusting the output
    values so that the original function (in the aptly named "function") is
    preserved for tracing. This fixes a bug where trace_kvm_cpuid() will
    trace the max function for a range instead of the requested function if
    the requested function is out-of-range and an entry for the max function
    exists.

    Fixes: 43561123ab37 ("kvm: x86: Improve emulation of CPUID leaves 0BH and 1FH")
    Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
    Cc: Jim Mattson <jmattson@google.com>
    Cc: Xiaoyao Li <xiaoyao.li@intel.com>
    Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    ---
    arch/x86/kvm/cpuid.c | 15 +++++++--------
    1 file changed, 7 insertions(+), 8 deletions(-)

    diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
    index b1c469446b07..6be012937eba 100644
    --- a/arch/x86/kvm/cpuid.c
    +++ b/arch/x86/kvm/cpuid.c
    @@ -997,12 +997,12 @@ static bool cpuid_function_in_range(struct kvm_vcpu *vcpu, u32 function)
    return max && function <= max->eax;
    }

    +/* Returns true if the requested leaf/function exists in guest CPUID. */
    bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
    u32 *ecx, u32 *edx, bool check_limit)
    {
    - u32 function = *eax, index = *ecx;
    + const u32 function = *eax, index = *ecx;
    struct kvm_cpuid_entry2 *entry;
    - struct kvm_cpuid_entry2 *max;
    bool found;

    entry = kvm_find_cpuid_entry(vcpu, function, index);
    @@ -1015,18 +1015,17 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
    */
    if (!entry && check_limit && !guest_cpuid_is_amd(vcpu) &&
    !cpuid_function_in_range(vcpu, function)) {
    - max = kvm_find_cpuid_entry(vcpu, 0, 0);
    - if (max) {
    - function = max->eax;
    - entry = kvm_find_cpuid_entry(vcpu, function, index);
    - }
    + entry = kvm_find_cpuid_entry(vcpu, 0, 0);
    + if (entry)
    + entry = kvm_find_cpuid_entry(vcpu, entry->eax, index);
    }
    if (entry) {
    *eax = entry->eax;
    *ebx = entry->ebx;
    *ecx = entry->ecx;
    *edx = entry->edx;
    - if (function == 7 && index == 0) {
    +
    + if (entry->function == 7 && index == 0) {
    u64 data;
    if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) &&
    (data & TSX_CTRL_CPUID_CLEAR))
    --
    2.24.1
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