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>

diff --git a/hw/i386/kvm/pci-assign.c b/hw/i386/kvm/pci-assign.c
index 0572821f2102496783b39ed6bea3a116156cf45b..de33657563f26e40fed76289fe5fbf335bbd2c65 100644 (file)
--- a/hw/i386/kvm/pci-assign.c
+++ b/hw/i386/kvm/pci-assign.c
@@ -1300,6 +1300,7 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev, Error **errp)
     if (pos != 0 && kvm_device_msix_supported(kvm_state)) {
         int bar_nr;
         uint32_t msix_table_entry;
+        uint16_t msix_max;
 
         verify_irqchip_in_kernel(&local_err);
         if (local_err) {
@@ -1315,9 +1316,10 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev, Error **errp)
         }
         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,
@@ -1327,9 +1329,7 @@ static int assigned_device_pci_cap_init(PCIDevice *pci_dev, Error **errp)
         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 */