Commit e6f8b6c1 authored by Xiaoyao Li's avatar Xiaoyao Li Committed by Borislav Petkov
Browse files

KVM: VMX: Extend VMXs #AC interceptor to handle split lock #AC in guest 



Two types of #AC can be generated in Intel CPUs:
 1. legacy alignment check #AC
 2. split lock #AC

Reflect #AC back into the guest if the guest has legacy alignment checks
enabled or if split lock detection is disabled.

If the #AC is not a legacy one and split lock detection is enabled, then
invoke handle_guest_split_lock() which will either warn and disable split
lock detection for this task or force SIGBUS on it.

[ tglx: Switch it to handle_guest_split_lock() and rename the misnamed
  helper function. ]

Suggested-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Link: https://lkml.kernel.org/r/20200410115517.176308876@linutronix.de
parent 9de6fe3c

arch/x86/kvm/vmx/vmx.c

+34 −3
Original line number Diff line number Diff line
@@ -4588,6 +4588,26 @@ static int handle_machine_check(struct kvm_vcpu *vcpu) 
	return 1;

}



/*

 * If the host has split lock detection disabled, then #AC is

 * unconditionally injected into the guest, which is the pre split lock

 * detection behaviour.

 *

 * If the host has split lock detection enabled then #AC is

 * only injected into the guest when:

 *  - Guest CPL == 3 (user mode)

 *  - Guest has #AC detection enabled in CR0

 *  - Guest EFLAGS has AC bit set

 */

static inline bool guest_inject_ac(struct kvm_vcpu *vcpu)

{

	if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))

		return true;



	return vmx_get_cpl(vcpu) == 3 && kvm_read_cr0_bits(vcpu, X86_CR0_AM) &&

	       (kvm_get_rflags(vcpu) & X86_EFLAGS_AC);

}



static int handle_exception_nmi(struct kvm_vcpu *vcpu)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -4653,9 +4673,6 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) 
		return handle_rmode_exception(vcpu, ex_no, error_code);



	switch (ex_no) {

	case AC_VECTOR:

		kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);

		return 1;

	case DB_VECTOR:

		dr6 = vmcs_readl(EXIT_QUALIFICATION);

		if (!(vcpu->guest_debug &
@@ -4684,6 +4701,20 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) 
		kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;

		kvm_run->debug.arch.exception = ex_no;

		break;

	case AC_VECTOR:

		if (guest_inject_ac(vcpu)) {

			kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);

			return 1;

		}



		/*

		 * Handle split lock. Depending on detection mode this will

		 * either warn and disable split lock detection for this

		 * task or force SIGBUS on it.

		 */

		if (handle_guest_split_lock(kvm_rip_read(vcpu)))

			return 1;

		fallthrough;

	default:

		kvm_run->exit_reason = KVM_EXIT_EXCEPTION;

		kvm_run->ex.exception = ex_no;

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