From 55dcef9d806aa530f10e3ca42eb24d52f850d674 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.

Count of slots increased to 509 later so we could increase limit

to 64 as some usecases require more than 32 devices.

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

---

 hw/vfio/pci.c | 29 ++++++++++++++++++++++++++++-

 hw/vfio/pci.h |  1 +

 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c

index 7b45353ce2..eb725a3aee 100644

--- a/hw/vfio/pci.c

+++ b/hw/vfio/pci.c

@@ -45,6 +45,9 @@

 #define TYPE_VFIO_PCI_NOHOTPLUG "vfio-pci-nohotplug"

+/* RHEL only: Set once for the first assigned dev */

+static uint16_t device_limit;

+

 static void vfio_disable_interrupts(VFIOPCIDevice *vdev);

 static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);

@@ -2807,9 +2810,30 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)

     ssize_t len;

     struct stat st;

     int groupid;

-    int i, ret;

+    int ret, i = 0;

     bool is_mdev;

+    if (device_limit && device_limit != vdev->assigned_device_limit) {

+            error_setg(errp, "Assigned device limit has been redefined. "

+                       "Old:%d, New:%d",

+                       device_limit, vdev->assigned_device_limit);

+            return;

+    } else {

+        device_limit = vdev->assigned_device_limit;

+    }

+

+    QLIST_FOREACH(group, &vfio_group_list, next) {

+        QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {

+            i++;

+        }

+    }

+

+    if (i >= vdev->assigned_device_limit) {

+        error_setg(errp, "Maximum supported vfio devices (%d) "

+                     "already attached", vdev->assigned_device_limit);

+        return;

+    }

+

     if (!vdev->vbasedev.sysfsdev) {

         if (!(~vdev->host.domain || ~vdev->host.bus ||

               ~vdev->host.slot || ~vdev->host.function)) {

@@ -3246,6 +3270,9 @@ static Property vfio_pci_dev_properties[] = {

     DEFINE_PROP_BOOL("x-no-kvm-msix", VFIOPCIDevice, no_kvm_msix, false),

     DEFINE_PROP_BOOL("x-no-geforce-quirks", VFIOPCIDevice,

                      no_geforce_quirks, false),

+    /* RHEL only */

+    DEFINE_PROP_UINT16("x-assigned-device-limit", VFIOPCIDevice,

+                       assigned_device_limit, 64),

     DEFINE_PROP_BOOL("x-no-kvm-ioeventfd", VFIOPCIDevice, no_kvm_ioeventfd,

                      false),

     DEFINE_PROP_BOOL("x-no-vfio-ioeventfd", VFIOPCIDevice, no_vfio_ioeventfd,

diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h

index 64777516d1..e0fe6ca97e 100644

--- a/hw/vfio/pci.h

+++ b/hw/vfio/pci.h

@@ -139,6 +139,7 @@ struct VFIOPCIDevice {

     EventNotifier err_notifier;

     EventNotifier req_notifier;

     int (*resetfn)(struct VFIOPCIDevice *);

+    uint16_t assigned_device_limit;

     uint32_t vendor_id;

     uint32_t device_id;

     uint32_t sub_vendor_id;

-- 

2.27.0