Patch "virtio_pci: fix cpu affinity support" has been added to the 4.12-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    virtio_pci: fix cpu affinity support

to the 4.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     virtio_pci-fix-cpu-affinity-support.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ba74b6f7fcc07355d087af6939712eed4a454821 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Thu, 24 Aug 2017 18:07:02 +0200
Subject: virtio_pci: fix cpu affinity support

From: Christoph Hellwig <hch@lst.de>

commit ba74b6f7fcc07355d087af6939712eed4a454821 upstream.

Commit 0b0f9dc5 ("Revert "virtio_pci: use shared interrupts for
virtqueues"") removed the adjustment of the pre_vectors for the virtio
MSI-X vector allocation which was added in commit fb5e31d9 ("virtio:
allow drivers to request IRQ affinity when creating VQs"). This will
lead to an incorrect assignment of MSI-X vectors, and potential
deadlocks when offlining cpus.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: 0b0f9dc5 ("Revert "virtio_pci: use shared interrupts for virtqueues")
Reported-by: YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/virtio/virtio_pci_common.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -107,6 +107,7 @@ static int vp_request_msix_vectors(struc
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 	const char *name = dev_name(&vp_dev->vdev.dev);
+	unsigned flags = PCI_IRQ_MSIX;
 	unsigned i, v;
 	int err = -ENOMEM;
 
@@ -126,10 +127,13 @@ static int vp_request_msix_vectors(struc
 					GFP_KERNEL))
 			goto error;
 
+	if (desc) {
+		flags |= PCI_IRQ_AFFINITY;
+		desc->pre_vectors++; /* virtio config vector */
+	}
+
 	err = pci_alloc_irq_vectors_affinity(vp_dev->pci_dev, nvectors,
-					     nvectors, PCI_IRQ_MSIX |
-					     (desc ? PCI_IRQ_AFFINITY : 0),
-					     desc);
+					     nvectors, flags, desc);
 	if (err < 0)
 		goto error;
 	vp_dev->msix_enabled = 1;


Patches currently in stable-queue which might be from hch@lst.de are

queue-4.12/virtio_pci-fix-cpu-affinity-support.patch
queue-4.12/x86-mm-fix-use-after-free-of-ldt_struct.patch
queue-4.12/dax-fix-deadlock-due-to-misaligned-pmd-faults.patch