msix: Add simple BAR allocation MSIX setup functions

msi_init() takes over a BAR without really specifying or allowing
specification of how it does so.  Instead, let's split it into
two interfaces, one fully specified, and one trivially easy.  This
implements the latter.  msix_init_exclusive_bar() takes over
allocating and filling a PCI BAR _exclusively_ for the use of MSIX.
When used, the matching msi_uninit_exclusive_bar() should be used
to tear it down.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/hw/msix.c b/hw/msix.c
index b64f109326..bafea94084 100644
--- a/hw/msix.c
+++ b/hw/msix.c
@@ -299,6 +299,45 @@ err_config:
     return ret;
 }
 
+int msix_init_exclusive_bar(PCIDevice *dev, unsigned short nentries,
+                            uint8_t bar_nr)
+{
+    int ret;
+    char *name;
+
+    /*
+     * Migration compatibility dictates that this remains a 4k
+     * BAR with the vector table in the lower half and PBA in
+     * the upper half.  Do not use these elsewhere!
+     */
+#define MSIX_EXCLUSIVE_BAR_SIZE 4096
+#define MSIX_EXCLUSIVE_BAR_PBA_OFFSET (MSIX_EXCLUSIVE_BAR_SIZE / 2)
+
+    if (nentries * PCI_MSIX_ENTRY_SIZE > MSIX_EXCLUSIVE_BAR_PBA_OFFSET) {
+        return -EINVAL;
+    }
+
+    if (asprintf(&name, "%s-msix", dev->name) == -1) {
+        return -ENOMEM;
+    }
+
+    memory_region_init(&dev->msix_exclusive_bar, name, MSIX_EXCLUSIVE_BAR_SIZE);
+
+    free(name);
+
+    ret = msix_init(dev, nentries, &dev->msix_exclusive_bar, bar_nr,
+                    MSIX_EXCLUSIVE_BAR_SIZE);
+    if (ret) {
+        memory_region_destroy(&dev->msix_exclusive_bar);
+        return ret;
+    }
+
+    pci_register_bar(dev, bar_nr, PCI_BASE_ADDRESS_SPACE_MEMORY,
+                     &dev->msix_exclusive_bar);
+
+    return 0;
+}
+
 static void msix_free_irq_entries(PCIDevice *dev)
 {
     int vector;
@@ -329,6 +368,14 @@ int msix_uninit(PCIDevice *dev, MemoryRegion *bar)
     return 0;
 }
 
+void msix_uninit_exclusive_bar(PCIDevice *dev)
+{
+    if (msix_present(dev)) {
+        msix_uninit(dev, &dev->msix_exclusive_bar);
+        memory_region_destroy(&dev->msix_exclusive_bar);
+    }
+}
+
 void msix_save(PCIDevice *dev, QEMUFile *f)
 {
     unsigned n = dev->msix_entries_nr;