KVM: s390: Use generic VIRT_XFER_TO_GUEST_WORK functions

Switch to using the generic infrastructure to check for and handle pending
work before transitioning into guest mode.

xfer_to_guest_mode_handle_work() does a few more things than the current
code does when deciding whether or not to exit the __vcpu_run() loop. The
exittime tests from kvm-unit-tests, in my tests, were within a few percent
compared to before this series, which is within noise tolerance.

Co-developed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
[frankja@linux.ibm.com: Removed semicolon]
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

Author: ajdlinux

arch/s390/kvm/Kconfig

@@ -30,6 +30,7 @@ config KVM
 	select HAVE_KVM_NO_POLL
 	select KVM_VFIO
 	select MMU_NOTIFIER
+	select VIRT_XFER_TO_GUEST_WORK
 	help
 	  Support hosting paravirtualized guest machines using the SIE
 	  virtualization capability on the mainframe. This should work

arch/s390/kvm/kvm-s390.c

@@ -14,6 +14,7 @@
 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 
 #include <linux/compiler.h>
+#include <linux/entry-virt.h>
 #include <linux/export.h>
 #include <linux/err.h>
 #include <linux/fs.h>
@@ -4675,9 +4676,6 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu)
 	vcpu->arch.sie_block->gg14 = vcpu->run->s.regs.gprs[14];
 	vcpu->arch.sie_block->gg15 = vcpu->run->s.regs.gprs[15];
 
-	if (need_resched())
-		schedule();
-
 	if (!kvm_is_ucontrol(vcpu->kvm)) {
 		rc = kvm_s390_deliver_pending_interrupts(vcpu);
 		if (rc || guestdbg_exit_pending(vcpu))
@@ -4982,12 +4980,12 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 	 */
 	kvm_vcpu_srcu_read_lock(vcpu);
 
-	do {
+	while (true) {
 		rc = vcpu_pre_run(vcpu);
+		kvm_vcpu_srcu_read_unlock(vcpu);
 		if (rc || guestdbg_exit_pending(vcpu))
 			break;
 
-		kvm_vcpu_srcu_read_unlock(vcpu);
 		/*
 		 * As PF_VCPU will be used in fault handler, between
 		 * guest_timing_enter_irqoff and guest_timing_exit_irqoff
@@ -4999,7 +4997,17 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 			       sizeof(sie_page->pv_grregs));
 		}
 
+xfer_to_guest_mode_check:
 		local_irq_disable();
+		xfer_to_guest_mode_prepare();
+		if (xfer_to_guest_mode_work_pending()) {
+			local_irq_enable();
+			rc = kvm_xfer_to_guest_mode_handle_work(vcpu);
+			if (rc)
+				break;
+			goto xfer_to_guest_mode_check;
+		}
+
 		guest_timing_enter_irqoff();
 		__disable_cpu_timer_accounting(vcpu);
 
@@ -5029,9 +5037,12 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 		kvm_vcpu_srcu_read_lock(vcpu);
 
 		rc = vcpu_post_run(vcpu, exit_reason);
-	} while (!signal_pending(current) && !guestdbg_exit_pending(vcpu) && !rc);
+		if (rc || guestdbg_exit_pending(vcpu)) {
+			kvm_vcpu_srcu_read_unlock(vcpu);
+			break;
+		}
+	}
 
-	kvm_vcpu_srcu_read_unlock(vcpu);
 	return rc;
 }
 

arch/s390/kvm/vsie.c

@@ -1180,12 +1180,23 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	current->thread.gmap_int_code = 0;
 	barrier();
 	if (!kvm_s390_vcpu_sie_inhibited(vcpu)) {
+xfer_to_guest_mode_check:
 		local_irq_disable();
+		xfer_to_guest_mode_prepare();
+		if (xfer_to_guest_mode_work_pending()) {
+			local_irq_enable();
+			rc = kvm_xfer_to_guest_mode_handle_work(vcpu);
+			if (rc)
+				goto skip_sie;
+			goto xfer_to_guest_mode_check;
+		}
 		guest_timing_enter_irqoff();
 		rc = kvm_s390_enter_exit_sie(scb_s, vcpu->run->s.regs.gprs, vsie_page->gmap->asce);
 		guest_timing_exit_irqoff();
 		local_irq_enable();
 	}
+
+skip_sie:
 	barrier();
 	vcpu->arch.sie_block->prog0c &= ~PROG_IN_SIE;
 
@@ -1345,13 +1356,11 @@ static int vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		 * 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) ||
+		if (kvm_s390_vcpu_has_irq(vcpu, 0) ||
 		    kvm_s390_vcpu_sie_inhibited(vcpu)) {
 			kvm_s390_rewind_psw(vcpu, 4);
 			break;
 		}
-		cond_resched();
 	}
 
 	if (rc == -EFAULT) {
@@ -1483,8 +1492,7 @@ int kvm_s390_handle_vsie(struct kvm_vcpu *vcpu)
 	if (unlikely(scb_addr & 0x1ffUL))
 		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)) {
+	if (kvm_s390_vcpu_has_irq(vcpu, 0) || kvm_s390_vcpu_sie_inhibited(vcpu)) {
 		kvm_s390_rewind_psw(vcpu, 4);
 		return 0;
 	}