[SRU][bionic:linux-azure-4.15][PATCH 1/1] UBUNTU: SAUCE: PCI: hv: Only reuse existing IRTE allocation for Multi-MSI

[John Cabaj]

BugLink: https://bugs.launchpad.net/bugs/1996093

Fixes b4b77778ecc5 ("PCI: hv: Reuse existing IRTE allocation in compose_msi_msg()")

Signed-off-by: John Cabaj <john.cabaj at canonical.com>
---
 drivers/pci/host/pci-hyperv.c | 68 +++++++++++++++++++++++++++--------
 1 file changed, 53 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 07100e7d87de..6465ac8d4193 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1101,7 +1101,7 @@ static void hv_pci_compose_compl(void *context, struct pci_response *resp,
 }
 
 static u32 hv_compose_msi_req_v1(
-	struct pci_create_interrupt *int_pkt, struct cpumask *affinity,
+	struct pci_create_interrupt *int_pkt,
 	u32 slot, u8 vector, u8 vector_count)
 {
 	int_pkt->message_type.type = PCI_CREATE_INTERRUPT_MESSAGE;
@@ -1119,23 +1119,48 @@ static u32 hv_compose_msi_req_v1(
 	return sizeof(*int_pkt);
 }
 
-static u32 hv_compose_msi_req_v2(
-	struct pci_create_interrupt2 *int_pkt, struct cpumask *affinity,
-	u32 slot, u8 vector, u8 vector_count)
+/*
+ * Create MSI w/ dummy vCPU set targeting just one vCPU, overwritten
+ * by subsequent retarget in hv_irq_unmask().
+ */
+static int hv_compose_msi_req_get_cpu(struct cpumask *affinity)
+{
+	return cpumask_first_and(affinity, cpu_online_mask);
+}
+
+/*
+ * Make sure the dummy vCPU values for multi-MSI don't all point to vCPU0.
+ */
+static int hv_compose_multi_msi_req_get_cpu(void)
 {
+	static DEFINE_SPINLOCK(multi_msi_cpu_lock);
+
+	/* -1 means starting with CPU 0 */
+	static int cpu_next = -1;
+
+	unsigned long flags;
 	int cpu;
 
+	spin_lock_irqsave(&multi_msi_cpu_lock, flags);
+
+	cpu_next = cpumask_next_wrap(cpu_next, cpu_online_mask, nr_cpu_ids,
+				     false);
+	cpu = cpu_next;
+
+	spin_unlock_irqrestore(&multi_msi_cpu_lock, flags);
+
+	return cpu;
+}
+
+static u32 hv_compose_msi_req_v2(
+	struct pci_create_interrupt2 *int_pkt, int cpu,
+	u32 slot, u8 vector, u8 vector_count)
+{
 	int_pkt->message_type.type = PCI_CREATE_INTERRUPT_MESSAGE2;
 	int_pkt->wslot.slot = slot;
 	int_pkt->int_desc.vector = vector;
 	int_pkt->int_desc.vector_count = vector_count;
 	int_pkt->int_desc.delivery_mode = dest_Fixed;
-
-	/*
-	 * Create MSI w/ dummy vCPU set targeting just one vCPU, overwritten
-	 * by subsequent retarget in hv_irq_unmask().
-	 */
-	cpu = cpumask_first_and(affinity, cpu_online_mask);
 	int_pkt->int_desc.processor_array[0] =
 		hv_cpu_number_to_vp_number(cpu);
 	int_pkt->int_desc.processor_count = 1;
@@ -1174,11 +1199,17 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		} int_pkts;
 	} __packed ctxt;
 
+	bool multi_msi;
 	u32 size;
 	int ret;
+	int cpu;
+
+	msi_desc  = irq_data_get_msi_desc(data);
+	multi_msi = !msi_desc->msi_attrib.is_msix &&
+		    msi_desc->nvec_used > 1;
 
 	/* Reuse the previous allocation */
-	if (data->chip_data) {
+	if (data->chip_data && multi_msi) {
 		int_desc = data->chip_data;
 		msg->address_hi = int_desc->address >> 32;
 		msg->address_lo = int_desc->address & 0xffffffff;
@@ -1186,7 +1217,6 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		return;
 	}
 
-	msi_desc = irq_data_get_msi_desc(data);
 	pdev = msi_desc_to_pci_dev(msi_desc);
 	dest = irq_data_get_effective_affinity_mask(data);
 	pbus = pdev->bus;
@@ -1194,12 +1224,19 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	hpdev = get_pcichild_wslot(hbus, devfn_to_wslot(pdev->devfn));
 	if (!hpdev)
 		goto return_null_message;
+ 
+	/* Free any previous message that might have already been composed. */
+	if (data->chip_data && !multi_msi) {
+		int_desc = data->chip_data;
+		data->chip_data = NULL;
+		hv_int_desc_free(hpdev, int_desc);
+	}
 
 	int_desc = kzalloc(sizeof(*int_desc), GFP_ATOMIC);
 	if (!int_desc)
 		goto drop_reference;
 
-	if (!msi_desc->msi_attrib.is_msix && msi_desc->nvec_used > 1) {
+	if (multi_msi) {
 		/*
 		 * If this is not the first MSI of Multi MSI, we already have
 		 * a mapping.  Can exit early.
@@ -1224,9 +1261,11 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		 */
 		vector = 32;
 		vector_count = msi_desc->nvec_used;
+		cpu = hv_compose_multi_msi_req_get_cpu();
 	} else {
 		vector = hv_msi_get_int_vector(data);
 		vector_count = 1;
+		cpu = hv_compose_msi_req_get_cpu(dest);
 	}
 
 	memset(&ctxt, 0, sizeof(ctxt));
@@ -1237,7 +1276,6 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	switch (pci_protocol_version) {
 	case PCI_PROTOCOL_VERSION_1_1:
 		size = hv_compose_msi_req_v1(&ctxt.int_pkts.v1,
-					dest,
 					hpdev->desc.win_slot.slot,
 					vector,
 					vector_count);
@@ -1246,7 +1284,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	case PCI_PROTOCOL_VERSION_1_2:
 	case PCI_PROTOCOL_VERSION_1_3:
 		size = hv_compose_msi_req_v2(&ctxt.int_pkts.v2,
-					dest,
+					cpu,
 					hpdev->desc.win_slot.slot,
 					vector,
 					vector_count);
-- 
2.34.1