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SubjectRe: [PATCH 1/6] KVM: x86: Fix tracing of CPUID.function when function is out-of-range
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On 02.03.20 20:57, Sean Christopherson wrote:
> 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))
>

What about the !entry case below this? It was impacted by the function
capping so far, not it's no longer.

Jan

--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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