Commit 33a729a1 authored by Eric Farman's avatar Eric Farman Committed by Janosch Frank
Browse files

KVM: s390: vsie: retry SIE instruction on host intercepts 



It's possible that SIE exits for work that the host needs to perform
rather than something that is intended for the guest.

A Linux guest will ignore this intercept code since there is nothing
for it to do, but a more robust solution would rewind the PSW back to
the SIE instruction. This will transparently resume the guest once
the host completes its work, without the guest needing to process
what is effectively a NOP and re-issue SIE itself.

Signed-off-by: default avatarEric Farman <farman@linux.ibm.com>
Acked-by: default avatarChristian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20240301204342.3217540-1-farman@linux.ibm.com


Signed-off-by: default avatarJanosch Frank <frankja@linux.ibm.com>
Message-ID: <20240301204342.3217540-1-farman@linux.ibm.com>
parent 98f77038

arch/s390/kvm/vsie.c

+19 −3
Original line number Diff line number Diff line
@@ -1304,10 +1304,24 @@ static int vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) 


		if (rc == -EAGAIN)

			rc = 0;

		if (rc || scb_s->icptcode || signal_pending(current) ||



		/*

		 * Exit the loop if the guest needs to process the intercept

		 */

		if (rc || scb_s->icptcode)

			break;



		/*

		 * Exit the loop if the host needs to process an intercept,

		 * but rewind the PSW to re-enter SIE once that's completed

		 * instead of passing a "no action" intercept to the guest.

		 */

		if (signal_pending(current) ||

		    kvm_s390_vcpu_has_irq(vcpu, 0) ||

		    kvm_s390_vcpu_sie_inhibited(vcpu))

		    kvm_s390_vcpu_sie_inhibited(vcpu)) {

			kvm_s390_rewind_psw(vcpu, 4);

			break;

		}

		cond_resched();

	}
@@ -1426,8 +1440,10 @@ int kvm_s390_handle_vsie(struct kvm_vcpu *vcpu) 
		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);



	if (signal_pending(current) || kvm_s390_vcpu_has_irq(vcpu, 0) ||

	    kvm_s390_vcpu_sie_inhibited(vcpu))

	    kvm_s390_vcpu_sie_inhibited(vcpu)) {

		kvm_s390_rewind_psw(vcpu, 4);

		return 0;

	}



	vsie_page = get_vsie_page(vcpu->kvm, scb_addr);

	if (IS_ERR(vsie_page))