| From | isaku.yamahata@intel ... | Subject | [RFC PATCH 25/67] KVM: x86: Allow host-initiated WRMSR to set X2APIC regardless of CPUID | Date | Mon, 16 Nov 2020 10:26:10 -0800 |
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From: Sean Christopherson <sean.j.christopherson@intel.com>
Let userspace, or in the case of TDX, KVM itself, enable X2APIC even if X2APIC is not reported as supported in the guest's CPU model. KVM generally does not force specific ordering between ioctls(), e.g. this forces userspace to configure CPUID before MSRs. And for TDX, vCPUs will always run with X2APIC enabled, e.g. KVM will want/need to enable X2APIC from time zero.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/x86.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8d58141256c5..a1c57d1eb460 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -394,8 +394,11 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info) { enum lapic_mode old_mode = kvm_get_apic_mode(vcpu); enum lapic_mode new_mode = kvm_apic_mode(msr_info->data); - u64 reserved_bits = ((~0ULL) << cpuid_maxphyaddr(vcpu)) | 0x2ff | - (guest_cpuid_has(vcpu, X86_FEATURE_X2APIC) ? 0 : X2APIC_ENABLE); + u64 reserved_bits = ((~0ULL) << cpuid_maxphyaddr(vcpu)) | 0x2ff; + + if (!msr_info->host_initiated && + !guest_cpuid_has(vcpu, X86_FEATURE_X2APIC)) + reserved_bits |= X2APIC_ENABLE; if ((msr_info->data & reserved_bits) != 0 || new_mode == LAPIC_MODE_INVALID) return 1; -- 2.17.1
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