Module Name:    src
Committed By:   thorpej
Date:           Sun Nov 19 19:49:44 UTC 2023

Modified Files:
        src/sys/dev/pci: virtio_pci.c

Log Message:
On alpha and sparc64, use VirtIO 1.0 and VIRTIO_F_ACCESS_PLATFORM so
that DMA to PCI-attached VirtIO devices works properly.  This is needed
for Qemu to select the appropriate address space for PCI DMA.


To generate a diff of this commit:
cvs rdiff -u -r1.43 -r1.44 src/sys/dev/pci/virtio_pci.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

Modified files:

Index: src/sys/dev/pci/virtio_pci.c
diff -u src/sys/dev/pci/virtio_pci.c:1.43 src/sys/dev/pci/virtio_pci.c:1.44
--- src/sys/dev/pci/virtio_pci.c:1.43	Fri Jul  7 07:19:36 2023
+++ src/sys/dev/pci/virtio_pci.c	Sun Nov 19 19:49:44 2023
@@ -1,4 +1,4 @@
-/* $NetBSD: virtio_pci.c,v 1.43 2023/07/07 07:19:36 rin Exp $ */
+/* $NetBSD: virtio_pci.c,v 1.44 2023/11/19 19:49:44 thorpej Exp $ */
 
 /*
  * Copyright (c) 2020 The NetBSD Foundation, Inc.
@@ -28,7 +28,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: virtio_pci.c,v 1.43 2023/07/07 07:19:36 rin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: virtio_pci.c,v 1.44 2023/11/19 19:49:44 thorpej Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -50,6 +50,15 @@ __KERNEL_RCSID(0, "$NetBSD: virtio_pci.c
 #define VIRTIO_PRIVATE
 #include <dev/pci/virtiovar.h> /* XXX: move to non-pci */
 
+#if defined(__alpha__) || defined(__sparc64__)
+/*
+ * XXX VIRTIO_F_ACCESS_PLATFORM is required for standard PCI DMA
+ * XXX to work on these platforms, at least by Qemu.
+ * XXX
+ * XXX Generalize this later.
+ */
+#define	__NEED_VIRTIO_F_ACCESS_PLATFORM
+#endif /* __alpha__ || __sparc64__ */
 
 #define VIRTIO_PCI_LOG(_sc, _use_log, _fmt, _args...)	\
 do {							\
@@ -275,8 +284,28 @@ virtio_pci_attach(device_t parent, devic
 		ret = virtio_pci_attach_10(self, aux);
 	}
 	if (ret == 0 && revision == 0) {
-		/* revision 0 means 0.9 only or both 0.9 and 1.0 */
+		/*
+		 * revision 0 means 0.9 only or both 0.9 and 1.0.  The
+		 * latter are so-called "Transitional Devices".  For
+		 * those devices, we want to use the 1.0 interface if
+		 * possible.
+		 *
+		 * XXX Currently only on platforms that require 1.0
+		 * XXX features, such as VIRTIO_F_ACCESS_PLATFORM.
+		 */
+#ifdef __NEED_VIRTIO_F_ACCESS_PLATFORM
+		/* First, try to attach 1.0 */
+		ret = virtio_pci_attach_10(self, aux);
+		if (ret != 0) {
+			aprint_error_dev(self,
+			    "VirtIO 1.0 error = %d, falling back to 0.9\n",
+			    ret);
+			/* Fall back to 0.9. */
+			ret = virtio_pci_attach_09(self, aux);
+		}
+#else
 		ret = virtio_pci_attach_09(self, aux);
+#endif /* __NEED_VIRTIO_F_ACCESS_PLATFORM */
 	}
 	if (ret) {
 		aprint_error_dev(self, "cannot attach (%d)\n", ret);
@@ -781,6 +810,10 @@ virtio_pci_negotiate_features_10(struct 
 	uint64_t host, negotiated, device_status;
 
 	guest_features |= VIRTIO_F_VERSION_1;
+#ifdef __NEED_VIRTIO_F_ACCESS_PLATFORM
+	/* XXX This could use some work. */
+	guest_features |= VIRTIO_F_ACCESS_PLATFORM;
+#endif /* __NEED_VIRTIO_F_ACCESS_PLATFORM */
 	/* notify on empty is 0.9 only */
 	guest_features &= ~VIRTIO_F_NOTIFY_ON_EMPTY;
 	sc->sc_active_features = 0;

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