pci-assign: limit # of msix vectors

KVM only supports MSIX table size up to 256 vectors,
but some assigned devices support more vectors,
at the moment attempts to assign them fail with EINVAL.

Tweak the MSIX capability exposed to guest to limit table size
to a supported value.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Gonglei <arei.gonglei@huawei.com>
Cc: qemu-stable@nongnu.org
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 639973a4740f38789057744b550df3a175bc49ad)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/i386/kvm/pci-assign.c b/hw/i386/kvm/pci-assign.c
index a825871d8a7c687fdf2feb2b1ae97fe17d89ce3b..76aa86e7b9cfe2a7f8183dc87192a3923ee608d7 100644 (file)
--- a/hw/i386/kvm/pci-assign.c
+++ b/hw/i386/kvm/pci-assign.c
@@ -1258,6 +1258,7 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
     if (pos != 0 && kvm_device_msix_supported(kvm_state)) {
         int bar_nr;
         uint32_t msix_table_entry;
+        uint16_t msix_max;
 
         if (!check_irqchip_in_kernel()) {
             return -ENOTSUP;
@@ -1269,9 +1270,10 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
         }
         pci_dev->msix_cap = pos;
 
-        pci_set_word(pci_dev->config + pos + PCI_MSIX_FLAGS,
-                     pci_get_word(pci_dev->config + pos + PCI_MSIX_FLAGS) &
-                     PCI_MSIX_FLAGS_QSIZE);
+        msix_max = (pci_get_word(pci_dev->config + pos + PCI_MSIX_FLAGS) &
+                    PCI_MSIX_FLAGS_QSIZE) + 1;
+        msix_max = MIN(msix_max, KVM_MAX_MSIX_PER_DEV);
+        pci_set_word(pci_dev->config + pos + PCI_MSIX_FLAGS, msix_max - 1);
 
         /* Only enable and function mask bits are writable */
         pci_set_word(pci_dev->wmask + pos + PCI_MSIX_FLAGS,
@@ -1281,9 +1283,7 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev)
         bar_nr = msix_table_entry & PCI_MSIX_FLAGS_BIRMASK;
         msix_table_entry &= ~PCI_MSIX_FLAGS_BIRMASK;
         dev->msix_table_addr = pci_region[bar_nr].base_addr + msix_table_entry;
-        dev->msix_max = pci_get_word(pci_dev->config + pos + PCI_MSIX_FLAGS);
-        dev->msix_max &= PCI_MSIX_FLAGS_QSIZE;
-        dev->msix_max += 1;
+        dev->msix_max = msix_max;
     }
 
     /* Minimal PM support, nothing writable, device appears to NAK changes */