From 0af267546b81d2b396f729c94bf8a29d89331e52 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg@kaod.org>
Date: Fri, 6 Mar 2020 16:01:40 +0100
Subject: [PATCH] powerpc/xive: Use XIVE_BAD_IRQ instead of zero to catch non
 configured IPIs
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commit b1a504a6500df50e83b701b7946b34fce27ad8a3 upstream.

When a CPU is brought up, an IPI number is allocated and recorded
under the XIVE CPU structure. Invalid IPI numbers are tracked with
interrupt number 0x0.

On the PowerNV platform, the interrupt number space starts at 0x10 and
this works fine. However, on the sPAPR platform, it is possible to
allocate the interrupt number 0x0 and this raises an issue when CPU 0
is unplugged. The XIVE spapr driver tracks allocated interrupt numbers
in a bitmask and it is not correctly updated when interrupt number 0x0
is freed. It stays allocated and it is then impossible to reallocate.

Fix by using the XIVE_BAD_IRQ value instead of zero on both platforms.

Reported-by: David Gibson <david@gibson.dropbear.id.au>
Fixes: eac1e731b59e ("powerpc/xive: guest exploitation of the XIVE interrupt controller")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200306150143.5551-2-clg@kaod.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
index c1d871d50a23..f9beccb7af37 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -68,13 +68,6 @@ static u32 xive_ipi_irq;
 /* Xive state for each CPU */
 static DEFINE_PER_CPU(struct xive_cpu *, xive_cpu);
 
-/*
- * A "disabled" interrupt should never fire, to catch problems
- * we set its logical number to this
- */
-#define XIVE_BAD_IRQ		0x7fffffff
-#define XIVE_MAX_IRQ		(XIVE_BAD_IRQ - 1)
-
 /* An invalid CPU target */
 #define XIVE_INVALID_TARGET	(-1)
 
@@ -1115,7 +1108,7 @@ static int xive_setup_cpu_ipi(unsigned int cpu)
 	xc = per_cpu(xive_cpu, cpu);
 
 	/* Check if we are already setup */
-	if (xc->hw_ipi != 0)
+	if (xc->hw_ipi != XIVE_BAD_IRQ)
 		return 0;
 
 	/* Grab an IPI from the backend, this will populate xc->hw_ipi */
@@ -1152,7 +1145,7 @@ static void xive_cleanup_cpu_ipi(unsigned int cpu, struct xive_cpu *xc)
 	/* Disable the IPI and free the IRQ data */
 
 	/* Already cleaned up ? */
-	if (xc->hw_ipi == 0)
+	if (xc->hw_ipi == XIVE_BAD_IRQ)
 		return;
 
 	/* Mask the IPI */
@@ -1308,6 +1301,7 @@ static int xive_prepare_cpu(unsigned int cpu)
 		if (np)
 			xc->chip_id = of_get_ibm_chip_id(np);
 		of_node_put(np);
+		xc->hw_ipi = XIVE_BAD_IRQ;
 
 		per_cpu(xive_cpu, cpu) = xc;
 	}
diff --git a/arch/powerpc/sysdev/xive/native.c b/arch/powerpc/sysdev/xive/native.c
index ad8ee7dd7f57..43f1f587a956 100644
--- a/arch/powerpc/sysdev/xive/native.c
+++ b/arch/powerpc/sysdev/xive/native.c
@@ -298,7 +298,7 @@ static void xive_native_put_ipi(unsigned int cpu, struct xive_cpu *xc)
 	s64 rc;
 
 	/* Free the IPI */
-	if (!xc->hw_ipi)
+	if (xc->hw_ipi == XIVE_BAD_IRQ)
 		return;
 	for (;;) {
 		rc = opal_xive_free_irq(xc->hw_ipi);
@@ -306,7 +306,7 @@ static void xive_native_put_ipi(unsigned int cpu, struct xive_cpu *xc)
 			msleep(OPAL_BUSY_DELAY_MS);
 			continue;
 		}
-		xc->hw_ipi = 0;
+		xc->hw_ipi = XIVE_BAD_IRQ;
 		break;
 	}
 }
diff --git a/arch/powerpc/sysdev/xive/spapr.c b/arch/powerpc/sysdev/xive/spapr.c
index 238207cd6bc3..ce756997054f 100644
--- a/arch/powerpc/sysdev/xive/spapr.c
+++ b/arch/powerpc/sysdev/xive/spapr.c
@@ -506,11 +506,11 @@ static int xive_spapr_get_ipi(unsigned int cpu, struct xive_cpu *xc)
 
 static void xive_spapr_put_ipi(unsigned int cpu, struct xive_cpu *xc)
 {
-	if (!xc->hw_ipi)
+	if (xc->hw_ipi == XIVE_BAD_IRQ)
 		return;
 
 	xive_irq_bitmap_free(xc->hw_ipi);
-	xc->hw_ipi = 0;
+	xc->hw_ipi = XIVE_BAD_IRQ;
 }
 #endif /* CONFIG_SMP */
 
diff --git a/arch/powerpc/sysdev/xive/xive-internal.h b/arch/powerpc/sysdev/xive/xive-internal.h
index 211725dbf364..a2f8d9361e6e 100644
--- a/arch/powerpc/sysdev/xive/xive-internal.h
+++ b/arch/powerpc/sysdev/xive/xive-internal.h
@@ -5,6 +5,13 @@
 #ifndef __XIVE_INTERNAL_H
 #define __XIVE_INTERNAL_H
 
+/*
+ * A "disabled" interrupt should never fire, to catch problems
+ * we set its logical number to this
+ */
+#define XIVE_BAD_IRQ		0x7fffffff
+#define XIVE_MAX_IRQ		(XIVE_BAD_IRQ - 1)
+
 /* Each CPU carry one of these with various per-CPU state */
 struct xive_cpu {
 #ifdef CONFIG_SMP
-- 
2.7.4