[PATCH v2 2/5] qtest/libqos/pci: Fix qpci_msix_enable sharing bar0

[Nicholas Piggin]

Devices where the MSI-X addresses are shared with other MMIO on BAR0
can not use msi_enable because it unmaps and remaps BAR0, which
interferes with device MMIO mappings. xhci-nec is one such device we
would like to test msix with.

Use the BAR iomap tracking structure introduced in the previous change
to have qpci_misx_enable() use existing iomaps if msix bars are
already mapped.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 tests/qtest/libqos/pci.h |  1 +
 tests/qtest/libqos/pci.c | 40 ++++++++++++++++++++++++++++++++++------
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/tests/qtest/libqos/pci.h b/tests/qtest/libqos/pci.h
index 9dc82ea723a..5a7b2454ad5 100644
--- a/tests/qtest/libqos/pci.h
+++ b/tests/qtest/libqos/pci.h
@@ -68,6 +68,7 @@ struct QPCIDevice
     bool bars_mapped[6];
     QPCIBar bars[6];
     bool msix_enabled;
+    bool msix_table_bar_iomap, msix_pba_bar_iomap;
     QPCIBar msix_table_bar, msix_pba_bar;
     uint64_t msix_table_off, msix_pba_off;
 };
diff --git a/tests/qtest/libqos/pci.c b/tests/qtest/libqos/pci.c
index a42ca08261d..023c1617680 100644
--- a/tests/qtest/libqos/pci.c
+++ b/tests/qtest/libqos/pci.c
@@ -288,15 +288,21 @@ void qpci_msix_enable(QPCIDevice *dev)
 
     table = qpci_config_readl(dev, addr + PCI_MSIX_TABLE);
     bir_table = table & PCI_MSIX_FLAGS_BIRMASK;
-    dev->msix_table_bar = qpci_iomap(dev, bir_table, NULL);
+    if (dev->bars_mapped[bir_table]) {
+        dev->msix_table_bar = dev->bars[bir_table];
+    } else {
+        dev->msix_table_bar_iomap = true;
+        dev->msix_table_bar = qpci_iomap(dev, bir_table, NULL);
+    }
     dev->msix_table_off = table & ~PCI_MSIX_FLAGS_BIRMASK;
 
     table = qpci_config_readl(dev, addr + PCI_MSIX_PBA);
     bir_pba = table & PCI_MSIX_FLAGS_BIRMASK;
-    if (bir_pba != bir_table) {
-        dev->msix_pba_bar = qpci_iomap(dev, bir_pba, NULL);
+    if (dev->bars_mapped[bir_pba]) {
+        dev->msix_pba_bar = dev->bars[bir_pba];
     } else {
-        dev->msix_pba_bar = dev->msix_table_bar;
+        dev->msix_pba_bar_iomap = true;
+        dev->msix_pba_bar = qpci_iomap(dev, bir_pba, NULL);
     }
     dev->msix_pba_off = table & ~PCI_MSIX_FLAGS_BIRMASK;
 
@@ -307,6 +313,7 @@ void qpci_msix_disable(QPCIDevice *dev)
 {
     uint8_t addr;
     uint16_t val;
+    uint32_t table;
 
     g_assert(dev->msix_enabled);
     addr = qpci_find_capability(dev, PCI_CAP_ID_MSIX, 0);
@@ -315,10 +322,31 @@ void qpci_msix_disable(QPCIDevice *dev)
     qpci_config_writew(dev, addr + PCI_MSIX_FLAGS,
                                                 val & ~PCI_MSIX_FLAGS_ENABLE);
 
-    if (dev->msix_pba_bar.addr != dev->msix_table_bar.addr) {
+    if (dev->msix_pba_bar_iomap) {
+        dev->msix_pba_bar_iomap = false;
         qpci_iounmap(dev, dev->msix_pba_bar);
+    } else {
+        /*
+         * If we had reused an existing iomap, ensure it is still mapped
+         * otherwise it would be a bug if it were unmapped before msix is
+         * disabled. A refcounting iomap implementation could avoid this
+         * issue entirely, but let's wait until that's needed.
+         */
+        uint8_t bir_pba;
+        table = qpci_config_readl(dev, addr + PCI_MSIX_PBA);
+        bir_pba = table & PCI_MSIX_FLAGS_BIRMASK;
+        g_assert(dev->bars_mapped[bir_pba]);
+    }
+
+    if (dev->msix_table_bar_iomap) {
+        dev->msix_table_bar_iomap = false;
+        qpci_iounmap(dev, dev->msix_table_bar);
+    } else {
+        uint8_t bir_table;
+        table = qpci_config_readl(dev, addr + PCI_MSIX_TABLE);
+        bir_table = table & PCI_MSIX_FLAGS_BIRMASK;
+        g_assert(dev->bars_mapped[bir_table]);
     }
-    qpci_iounmap(dev, dev->msix_table_bar);
 
     dev->msix_enabled = 0;
     dev->msix_table_off = 0;
-- 
2.45.2