From dcf1c9f485cefd4dad8040efb9555f33a118074b Mon Sep 17 00:00:00 2001
From: Bandan Das <bsd@redhat.com>
Date: Tue, 3 Dec 2013 20:05:13 +0100
Subject: vfio: cap number of devices that can be assigned

RH-Author: Bandan Das <bsd@redhat.com>
Message-id: <1386101113-31560-3-git-send-email-bsd@redhat.com>
Patchwork-id: 55984
O-Subject: [PATCH RHEL7 qemu-kvm v2 2/2] vfio: cap number of devices that can be assigned
Bugzilla: 678368
RH-Acked-by: Alex Williamson <alex.williamson@redhat.com>
RH-Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>

Go through all groups to get count of total number of devices
active to enforce limit

Reasoning from Alex for the limit(32) - Assuming 3 slots per
device, with 125 slots (number of memory slots for RHEL 7),
we can support almost 40 devices and still have few slots left
for other uses. Stepping down a bit, the number 32 arbitrarily
matches the number of slots on a PCI bus and is also a nice power
of two.

Signed-off-by: Bandan Das <bsd@redhat.com>

Rebase notes (2.8.0):
- removed return value for vfio_realize (commit 1a22aca)

Merged patches (2.9.0):
- 17eb774 vfio: Use error_setg when reporting max assigned device overshoot

(cherry picked from commit 9fa3c9fc6dfcde76d80db1aa601b2d577f72ceec)
(cherry picked from commit 3cb35556dc7d994f203d732fe952f95fcdb03c0a)
(cherry picked from commit 17e46c50515e8935c0f99a868fe07bd3c92a4586)
(cherry picked from commit 726bd82965a9e1a58065a3226597b3c2bafdbf68)
(cherry picked from commit efd8c5d78242c2e0892e165b75d2c8f1afb172a6)
---
 hw/vfio/pci.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index b9bc6cd..34b9d19 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -35,6 +35,7 @@
 #include "qapi/error.h"
 
 #define MSIX_CAP_LENGTH 12
+#define MAX_DEV_ASSIGN_CMDLINE 32
 
 static void vfio_disable_interrupts(VFIOPCIDevice *vdev);
 static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
@@ -2807,7 +2808,19 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
     ssize_t len;
     struct stat st;
     int groupid;
-    int i, ret;
+    int ret, i = 0;
+
+    QLIST_FOREACH(group, &vfio_group_list, next) {
+        QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
+            i++;
+        }
+    }
+
+    if (i >= MAX_DEV_ASSIGN_CMDLINE) {
+        error_setg(errp, "Maximum supported vfio devices (%d) "
+                     "already attached", MAX_DEV_ASSIGN_CMDLINE);
+        return;
+    }
 
     if (!vdev->vbasedev.sysfsdev) {
         if (!(~vdev->host.domain || ~vdev->host.bus ||
-- 
1.8.3.1