KVM: X86: Processor States following Reset or INIT

- XCR0 is reset to 1 by RESET but not INIT
- XSS is zeroed by both RESET and INIT
- BNDCFGU, BND0-BND3, BNDCFGS, BNDSTATUS are zeroed by both RESET and INIT

This patch does this according to SDM.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Jim Mattson <jmattson@google.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -5581,6 +5581,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	vmcs_write32(GUEST_ACTIVITY_STATE, GUEST_ACTIVITY_ACTIVE);
 	vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, 0);
 	vmcs_writel(GUEST_PENDING_DBG_EXCEPTIONS, 0);
+	if (kvm_mpx_supported())
+		vmcs_write64(GUEST_BNDCFGS, 0);
 
 	setup_msrs(vmx);
 

arch/x86/kvm/x86.c

@@ -7804,18 +7804,40 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	kvm_async_pf_hash_reset(vcpu);
 	vcpu->arch.apf.halted = false;
 
+	if (kvm_mpx_supported()) {
+		void *mpx_state_buffer;
+
+		/*
+		 * To avoid have the INIT path from kvm_apic_has_events() that be
+		 * called with loaded FPU and does not let userspace fix the state.
+		 */
+		kvm_put_guest_fpu(vcpu);
+		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave,
+					XFEATURE_MASK_BNDREGS);
+		if (mpx_state_buffer)
+			memset(mpx_state_buffer, 0, sizeof(struct mpx_bndreg_state));
+		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave,
+					XFEATURE_MASK_BNDCSR);
+		if (mpx_state_buffer)
+			memset(mpx_state_buffer, 0, sizeof(struct mpx_bndcsr));
+	}
+
 	if (!init_event) {
 		kvm_pmu_reset(vcpu);
 		vcpu->arch.smbase = 0x30000;
 
 		vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT;
 		vcpu->arch.msr_misc_features_enables = 0;
+
+		vcpu->arch.xcr0 = XFEATURE_MASK_FP;
 	}
 
 	memset(vcpu->arch.regs, 0, sizeof(vcpu->arch.regs));
 	vcpu->arch.regs_avail = ~0;
 	vcpu->arch.regs_dirty = ~0;
 
+	vcpu->arch.ia32_xss = 0;
+
 	kvm_x86_ops->vcpu_reset(vcpu, init_event);
 }