kvm: nVMX: Allow L1 to intercept software exceptions (#BP and #OF)

When L2 exits to L0 due to "exception or NMI", software exceptions
(#BP and #OF) for which L1 has requested an intercept should be
handled by L1 rather than L0. Previously, only hardware exceptions
were forwarded to L1.

Signed-off-by: Jim Mattson <jmattson@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
	/*
	 * Pass through host's Machine Check Enable value to hw_cr4, which
	 * is in force while we are in guest mode.  Do not let guests control
	 * this bit, even if host CR4.MCE == 0.
	 */
	unsigned long hw_cr4 =
		(cr4_read_shadow() & X86_CR4_MCE) |
		(cr4 & ~X86_CR4_MCE) |
		(to_vmx(vcpu)->rmode.vm86_active ?
		 KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);

	if (cr4 & X86_CR4_VMXE) {
		/*
		 * To use VMXON (and later other VMX instructions), a guest
		 * must first be able to turn on cr4.VMXE (see handle_vmon()).
		 * So basically the check on whether to allow nested VMX
		 * is here.
		 */
		if (!nested_vmx_allowed(vcpu))
			return 1;
	}

	if (to_vmx(vcpu)->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
		return 1;

	vcpu->arch.cr4 = cr4;
	if (enable_ept) {
		if (!is_paging(vcpu)) {
			hw_cr4 &= ~X86_CR4_PAE;
			hw_cr4 |= X86_CR4_PSE;
		} else if (!(cr4 & X86_CR4_PAE)) {
			hw_cr4 &= ~X86_CR4_PAE;
		}
	}

	if (!enable_unrestricted_guest && !is_paging(vcpu))
		/*
		 * SMEP/SMAP/PKU is disabled if CPU is in non-paging mode in
		 * hardware.  To emulate this behavior, SMEP/SMAP/PKU needs
		 * to be manually disabled when guest switches to non-paging
		 * mode.
		 *
		 * If !enable_unrestricted_guest, the CPU is always running
		 * with CR0.PG=1 and CR4 needs to be modified.
		 * If enable_unrestricted_guest, the CPU automatically
		 * disables SMEP/SMAP/PKU when the guest sets CR0.PG=0.
		 */
		hw_cr4 &= ~(X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_PKE);

	vmcs_writel(CR4_READ_SHADOW, cr4);
	vmcs_writel(GUEST_CR4, hw_cr4);
	return 0;
}

static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
	/*
	 * Pass through host's Machine Check Enable value to hw_cr4, which
	 * is in force while we are in guest mode.  Do not let guests control
	 * this bit, even if host CR4.MCE == 0.
	 */
	unsigned long hw_cr4 =
		(cr4_read_shadow() & X86_CR4_MCE) |
		(cr4 & ~X86_CR4_MCE) |
		(to_vmx(vcpu)->rmode.vm86_active ?
		 KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);

	if (cr4 & X86_CR4_VMXE) {
		/*
		 * To use VMXON (and later other VMX instructions), a guest
		 * must first be able to turn on cr4.VMXE (see handle_vmon()).
		 * So basically the check on whether to allow nested VMX
		 * is here.
		 */
		if (!nested_vmx_allowed(vcpu))
			return 1;
	}

	if (to_vmx(vcpu)->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
		return 1;

	vcpu->arch.cr4 = cr4;
	if (enable_ept) {
		if (!is_paging(vcpu)) {
			hw_cr4 &= ~X86_CR4_PAE;
			hw_cr4 |= X86_CR4_PSE;
		} else if (!(cr4 & X86_CR4_PAE)) {
			hw_cr4 &= ~X86_CR4_PAE;
		}
	}

	if (!enable_unrestricted_guest && !is_paging(vcpu))
		/*
		 * SMEP/SMAP/PKU is disabled if CPU is in non-paging mode in
		 * hardware.  To emulate this behavior, SMEP/SMAP/PKU needs
		 * to be manually disabled when guest switches to non-paging
		 * mode.
		 *
		 * If !enable_unrestricted_guest, the CPU is always running
		 * with CR0.PG=1 and CR4 needs to be modified.
		 * If enable_unrestricted_guest, the CPU automatically
		 * disables SMEP/SMAP/PKU when the guest sets CR0.PG=0.
		 */
		hw_cr4 &= ~(X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_PKE);

	vmcs_writel(CR4_READ_SHADOW, cr4);
	vmcs_writel(GUEST_CR4, hw_cr4);
	return 0;
}
