linux-kernel - [PATCH 1/2] pci-hyperv: Fix a bug in specifying CPU affinity

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Date:   Fri, 24 Mar 2017 11:07:21 -0700
From:   kys@...hange.microsoft.com
To:     helgaas@...nel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
        olaf@...fle.de, apw@...onical.com, vkuznets@...hat.com,
        jasowang@...hat.com, leann.ogasawara@...onical.com,
        marcelo.cerri@...onical.com, sthemmin@...rosoft.com
Cc:     "K. Y. Srinivasan" <kys@...rosoft.com>, <stable@...r.kernel.org>
Subject: [PATCH 1/2] pci-hyperv: Fix a bug in specifying CPU affinity

From: K. Y. Srinivasan <kys@...rosoft.com>

When we have 32 or more CPUs in the affinity mask, we should
use a special constant to specify that to the host. Fix this issue.

Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
Cc: <stable@...r.kernel.org>
---
 drivers/pci/host/pci-hyperv.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index ada9856..32a16fb 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -72,6 +72,7 @@ enum {
 	PCI_PROTOCOL_VERSION_CURRENT = PCI_PROTOCOL_VERSION_1_1
 };
 
+#define CPU_AFFINITY_ALL	-1ULL
 #define PCI_CONFIG_MMIO_LENGTH	0x2000
 #define CFG_PAGE_OFFSET 0x1000
 #define CFG_PAGE_SIZE (PCI_CONFIG_MMIO_LENGTH - CFG_PAGE_OFFSET)
@@ -897,9 +898,13 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	 * processors because Hyper-V only supports 64 in a guest.
 	 */
 	affinity = irq_data_get_affinity_mask(data);
-	for_each_cpu_and(cpu, affinity, cpu_online_mask) {
-		int_pkt->int_desc.cpu_mask |=
-			(1ULL << vmbus_cpu_number_to_vp_number(cpu));
+	if (cpumask_weight(affinity) >= 32) {
+		int_pkt->int_desc.cpu_mask = CPU_AFFINITY_ALL;
+	} else {
+		for_each_cpu_and(cpu, affinity, cpu_online_mask) {
+			int_pkt->int_desc.cpu_mask |=
+				(1ULL << vmbus_cpu_number_to_vp_number(cpu));
+		}
 	}
 
 	ret = vmbus_sendpacket(hpdev->hbus->hdev->channel, int_pkt,
-- 
1.7.1