Sean Christopherson <sean.j.christopherson@xxxxxxxxx> writes:
> @@ -4623,6 +4623,12 @@ static int handle_machine_check(struct kvm_vcpu *vcpu)
> return 1;
> }
>
> +static inline bool guest_cpu_alignment_check_enabled(struct kvm_vcpu *vcpu)
I used a different function name intentionally so the check for 'guest
want's split lock #AC' can go there as well once it's sorted.
> +{
> + 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);
> @@ -4688,9 +4694,6 @@ 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 &
> @@ -4719,6 +4722,27 @@ 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:
> + /*
> + * Reflect #AC to the guest if it's expecting the #AC, i.e. has
> + * legacy alignment check enabled. Pre-check host split lock
> + * turned on to avoid the VMREADs needed to check legacy #AC,
> + * i.e. reflect the #AC if the only possible source is legacy
> + * alignment checks.
> + */
> + if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT) ||
I think the right thing to do here is to make this really independent of
that feature, i.e. inject the exception if
(CPL==3 && CR0.AM && EFLAGS.AC) || (FUTURE && (GUEST_TEST_CTRL & SLD))
iow. when its really clear that the guest asked for it. If there is an
actual #AC with SLD disabled and !(CPL==3 && CR0.AM && EFLAGS.AC) then
something is badly wrong and the thing should just die. That's why I
separated handle_guest_split_lock() and tell about that case.
Thanks,
tglx
