Commit 86e2de10eb14 for kernel

commit 86e2de10eb14446a49019791bd0674faa5fae088
Author: Sean Christopherson <seanjc@google.com>
Date:   Fri May 22 10:35:25 2026 -0700

    KVM: x86: Return the VM's configured APIC bus frequency when queried

    When KVM_CAP_X86_APIC_BUS_CYCLES_NS is queried on a specific VM, return the
    VM's configured APIC bus frequency, not KVM's default.  Aside from the fact
    that returning the default frequency is blatantly wrong if userspace has
    changed the frequency, returning the configured frequency means userspace
    can blindly trust the result, e.g. when filling PV CPUID information that
    communicates the APIC bus frequency to the guest.

    Fixes: 6fef518594bc ("KVM: x86: Add a capability to configure bus frequency for APIC timer")
    Reported-by: David Woodhouse <dwmw2@infradead.org>
    Closes: https://lore.kernel.org/all/ab84153e33fbe7c25667f595c56b310d4d5a93ef.camel@infradead.org
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    Message-ID: <20260522173526.3539407-2-seanjc@google.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0a1b63c63d1a..c1a72d749084 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4876,7 +4876,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = tdp_enabled;
 		break;
 	case KVM_CAP_X86_APIC_BUS_CYCLES_NS:
-		r = APIC_BUS_CYCLE_NS_DEFAULT;
+		r = kvm ? kvm->arch.apic_bus_cycle_ns : APIC_BUS_CYCLE_NS_DEFAULT;
 		break;
 	case KVM_CAP_EXIT_HYPERCALL:
 		r = KVM_EXIT_HYPERCALL_VALID_MASK;