add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/s390/kvm/intercept.c
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@@ -270,10 +270,18 @@
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 /**
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  * handle_external_interrupt - used for external interruption interceptions
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  *
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- * This interception only occurs if the CPUSTAT_EXT_INT bit was set, or if
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- * the new PSW does not have external interrupts disabled. In the first case,
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- * we've got to deliver the interrupt manually, and in the second case, we
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- * drop to userspace to handle the situation there.
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+ * This interception occurs if:
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+ * - the CPUSTAT_EXT_INT bit was already set when the external interrupt
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+ *   occurred. In this case, the interrupt needs to be injected manually to
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+ *   preserve interrupt priority.
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+ * - the external new PSW has external interrupts enabled, which will cause an
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+ *   interruption loop. We drop to userspace in this case.
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+ *
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+ * The latter case can be detected by inspecting the external mask bit in the
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+ * external new psw.
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+ *
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+ * Under PV, only the latter case can occur, since interrupt priorities are
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+ * handled in the ultravisor.
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  */
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 static int handle_external_interrupt(struct kvm_vcpu *vcpu)
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 {
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@@ -284,10 +292,18 @@
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 	vcpu->stat.exit_external_interrupt++;
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294
 
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-	rc = read_guest_lc(vcpu, __LC_EXT_NEW_PSW, &newpsw, sizeof(psw_t));
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-	if (rc)
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-		return rc;
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-	/* We can not handle clock comparator or timer interrupt with bad PSW */
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+	if (kvm_s390_pv_cpu_is_protected(vcpu)) {
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+		newpsw = vcpu->arch.sie_block->gpsw;
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+	} else {
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+		rc = read_guest_lc(vcpu, __LC_EXT_NEW_PSW, &newpsw, sizeof(psw_t));
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+		if (rc)
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+			return rc;
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+	}
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+
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+	/*
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+	 * Clock comparator or timer interrupt with external interrupt enabled
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+	 * will cause interrupt loop. Drop to userspace.
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+	 */
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 	if ((eic == EXT_IRQ_CLK_COMP || eic == EXT_IRQ_CPU_TIMER) &&
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 	    (newpsw.mask & PSW_MASK_EXT))
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 		return -EOPNOTSUPP;
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@@ -371,8 +387,8 @@
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  */
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 int handle_sthyi(struct kvm_vcpu *vcpu)
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 {
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-	int reg1, reg2, r = 0;
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-	u64 code, addr, cc = 0, rc = 0;
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+	int reg1, reg2, cc = 0, r = 0;
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+	u64 code, addr, rc = 0;
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 	struct sthyi_sctns *sctns = NULL;
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 	if (!test_kvm_facility(vcpu->kvm, 74))
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@@ -403,7 +419,10 @@
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 		return -ENOMEM;
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 	cc = sthyi_fill(sctns, &rc);
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-
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+	if (cc < 0) {
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+		free_page((unsigned long)sctns);
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+		return cc;
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+	}
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 out:
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 	if (!cc) {
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 		if (kvm_s390_pv_cpu_is_protected(vcpu)) {