Commit ed351c57 authored by Gautam Menghani's avatar Gautam Menghani Committed by Michael Ellerman
Browse files

Revert "KVM: PPC: Book3S HV Nested: Stop forwarding all HFUs to L1" 



This reverts commit 7c3ded57.

On PowerNV, when a nested guest tries to use a feature prohibited by
HFSCR, the nested hypervisor (L1) should get a H_FAC_UNAVAILABLE trap
so that L1 can emulate the feature. But with the change introduced by
commit 7c3ded57 ("KVM: PPC: Book3S HV Nested: Stop forwarding all HFUs
to L1") the L1 ends up getting a H_EMUL_ASSIST because of which, the L1
ends up injecting a SIGILL when L2 (nested guest) tries to use doorbells.

Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarGautam Menghani <gautam@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241109063301.105289-2-gautam@linux.ibm.com
parent 96e266e3

arch/powerpc/kvm/book3s_hv.c

+2 −29
Original line number Diff line number Diff line
@@ -2063,36 +2063,9 @@ static int kvmppc_handle_nested_exit(struct kvm_vcpu *vcpu) 
		fallthrough; /* go to facility unavailable handler */

#endif



	case BOOK3S_INTERRUPT_H_FAC_UNAVAIL: {

		u64 cause = vcpu->arch.hfscr >> 56;



		/*

		 * Only pass HFU interrupts to the L1 if the facility is

		 * permitted but disabled by the L1's HFSCR, otherwise

		 * the interrupt does not make sense to the L1 so turn

		 * it into a HEAI.

		 */

		if (!(vcpu->arch.hfscr_permitted & (1UL << cause)) ||

				(vcpu->arch.nested_hfscr & (1UL << cause))) {

			ppc_inst_t pinst;

			vcpu->arch.trap = BOOK3S_INTERRUPT_H_EMUL_ASSIST;



			/*

			 * If the fetch failed, return to guest and

			 * try executing it again.

			 */

			r = kvmppc_get_last_inst(vcpu, INST_GENERIC, &pinst);

			vcpu->arch.emul_inst = ppc_inst_val(pinst);

			if (r != EMULATE_DONE)

				r = RESUME_GUEST;

			else

				r = RESUME_HOST;

		} else {

	case BOOK3S_INTERRUPT_H_FAC_UNAVAIL:

		r = RESUME_HOST;

		}



		break;

	}



	case BOOK3S_INTERRUPT_HV_RM_HARD:

		vcpu->arch.trap = 0;