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From 3cb35556dc7d994f203d732fe952f95fcdb03c0a Mon Sep 17 00:00:00 2001
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From: Bandan Das <bsd@redhat.com>
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Date: Tue, 3 Dec 2013 20:05:13 +0100
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Subject: vfio: cap number of devices that can be assigned
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RH-Author: Bandan Das <bsd@redhat.com>
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Message-id: <1386101113-31560-3-git-send-email-bsd@redhat.com>
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Patchwork-id: 55984
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O-Subject: [PATCH RHEL7 qemu-kvm v2 2/2] vfio: cap number of devices that can be assigned
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Bugzilla: 678368
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RH-Acked-by: Alex Williamson <alex.williamson@redhat.com>
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RH-Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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Go through all groups to get count of total number of devices
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active to enforce limit
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Reasoning from Alex for the limit(32) - Assuming 3 slots per
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device, with 125 slots (number of memory slots for RHEL 7),
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we can support almost 40 devices and still have few slots left
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for other uses. Stepping down a bit, the number 32 arbitrarily
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matches the number of slots on a PCI bus and is also a nice power
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of two.
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Signed-off-by: Bandan Das <bsd@redhat.com>
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Rebase notes (2.8.0):
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- removed return value for vfio_realize (commit 1a22aca)
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Merged patches (2.9.0):
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- 17eb774 vfio: Use error_setg when reporting max assigned device overshoot
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(cherry picked from commit 9fa3c9fc6dfcde76d80db1aa601b2d577f72ceec)
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---
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hw/vfio/pci.c | 15 ++++++++++++++-
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1 file changed, 14 insertions(+), 1 deletion(-)
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diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
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index 31e1edf..f3f1ce6 100644
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--- a/hw/vfio/pci.c
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+++ b/hw/vfio/pci.c
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@@ -34,6 +34,7 @@
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#include "qapi/error.h"
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#define MSIX_CAP_LENGTH 12
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+#define MAX_DEV_ASSIGN_CMDLINE 32
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static void vfio_disable_interrupts(VFIOPCIDevice *vdev);
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static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
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@@ -2639,7 +2640,19 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
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ssize_t len;
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struct stat st;
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int groupid;
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- int i, ret;
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+ int ret, i = 0;
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+
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+ QLIST_FOREACH(group, &vfio_group_list, next) {
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+ QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
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+ i++;
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+ }
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+ }
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+
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+ if (i >= MAX_DEV_ASSIGN_CMDLINE) {
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+ error_setg(errp, "Maximum supported vfio devices (%d) "
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+ "already attached", MAX_DEV_ASSIGN_CMDLINE);
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+ return;
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+ }
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if (!vdev->vbasedev.sysfsdev) {
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if (!(~vdev->host.domain || ~vdev->host.bus ||
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--
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1.8.3.1
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