From: Like Xu <likexu@xxxxxxxxxxx> Some of the new Intel PT capabilities (e.g. SDM Vol3, 32.2.4 Event Tracing, it exposes details about the asynchronous events, when they are generated, and when their corresponding software event handler completes execution) cannot be safely and fully emulated by the KVM, especially emulating the simultaneous writing of guest PT packets generated by the KVM to the guest PT buffer. For KVM, it's better to advertise currently supported features based on the "static struct pt_cap_desc" implemented in the host PT driver and ignore _all_ unknown features before they have been investigated one by one and supported in a safe manner, leaving the rest as system-wide-only tracing capabilities. Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Like Xu <likexu@xxxxxxxxxxx> --- v1 -> v2 Changelog: - Be safe and ignore _all_ unknown capabilities. (Paolo) Previous: https://lore.kernel.org/kvm/20220106085533.84356-1-likexu@xxxxxxxxxxx/ arch/x86/kvm/cpuid.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 0b920e12bb6d..439b93359848 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -901,6 +901,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) break; } + /* It's better to be safe and ignore _all_ unknown capabilities. */ + entry->ebx &= GENMASK(5, 0); for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) { if (!do_host_cpuid(array, function, i)) goto out; -- 2.33.1
