vfio/common: Add a trace point when a MMIO RAM section cannot be mapped

The MSI-X structures of some devices and other non-MSI-X structures
may be in the same BAR. They may share one host page, especially in
the case of large page granularity, such as 64K.

For example, MSIX-Table size of 82599 NIC is 0x30 and the offset in
Bar 3(size 64KB) is 0x0. vfio_listener_region_add() will be called
to map the remaining range (0x30-0xffff). If host page size is 64KB,
it will return early at 'int128_ge((int128_make64(iova), llend))'
without any message. Let's add a trace point to inform users like commit
5c08600547c0 ("vfio: Use a trace point when a RAM section cannot be DMA mapped")
did.

Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Link: https://lore.kernel.org/r/20211027090406.761-3-jiangkunkun@huawei.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index a784b219e6..dd387b0d39 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -893,6 +893,13 @@ static void vfio_listener_region_add(MemoryListener *listener,
     llend = int128_and(llend, int128_exts64(qemu_real_host_page_mask));
 
     if (int128_ge(int128_make64(iova), llend)) {
+        if (memory_region_is_ram_device(section->mr)) {
+            trace_vfio_listener_region_add_no_dma_map(
+                memory_region_name(section->mr),
+                section->offset_within_address_space,
+                int128_getlo(section->size),
+                qemu_real_host_page_size);
+        }
         return;
     }
     end = int128_get64(int128_sub(llend, int128_one()));