Hyper-V: vmbus: implementat bus_get_dma_tag in vmbus

In ARM64 Hyper-V UFS filesystem is getting corruption and those
corruptions are consistently happening just after hitting a page
boundary. It is unable to correctly read disk blocks into buffers
that are not aligned to 512-byte boundaries.

It happens because storvsc needs physically contiguous memory which
may not be the case when bus_dma needs to create a bounce buffer.
This can happen when the destination is not cache-line aligned.

Hyper-V VMs have VMbus synthetic devices and PCI pass-thru devices
that are added dynamically via the VMbus protocol and are not
represented in the ACPI DSDT. Only the top level VMbus node exists
in the DSDT. As such, on ARM64 these devices don't pick up coherence
information and default to not hardware coherent.

PR:		267654, 272666
Reviewed by:	andrew, whu
Tested by:	lwhsu
MFC after:	3 days
Sponsored by:	Microsoft
Differential Revision:	https://reviews.freebsd.org/D41728

2 files changed, 34 insertions, 0 deletions

diff --git a/sys/dev/hyperv/vmbus/vmbus.c b/sys/dev/hyperv/vmbus/vmbus.c
index e0f7bbc99ca7..ee412e643b4f 100644
--- a/sys/dev/hyperv/vmbus/vmbus.c
+++ b/sys/dev/hyperv/vmbus/vmbus.c
@@ -137,6 +137,7 @@ static void			vmbus_intr_teardown(struct vmbus_softc *);
 static int			vmbus_doattach(struct vmbus_softc *);
 static void			vmbus_event_proc_dummy(struct vmbus_softc *,
 				    int);
+static bus_dma_tag_t	vmbus_get_dma_tag(device_t parent, device_t child);
 static struct vmbus_softc	*vmbus_sc;
 
 SYSCTL_NODE(_hw, OID_AUTO, vmbus, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
@@ -183,6 +184,7 @@ static device_method_t vmbus_methods[] = {
 	DEVMETHOD(bus_setup_intr,		bus_generic_setup_intr),
 	DEVMETHOD(bus_teardown_intr,		bus_generic_teardown_intr),
 	DEVMETHOD(bus_get_cpus,			bus_generic_get_cpus),
+	DEVMETHOD(bus_get_dma_tag,		vmbus_get_dma_tag),
 
 	/* pcib interface */
 	DEVMETHOD(pcib_alloc_msi,		vmbus_alloc_msi),
@@ -219,6 +221,13 @@ vmbus_get_softc(void)
 	return vmbus_sc;
 }
 
+static bus_dma_tag_t
+vmbus_get_dma_tag(device_t dev, device_t child)
+{
+	struct vmbus_softc *sc = vmbus_get_softc();
+	return (sc->dmat);
+}
+
 void
 vmbus_msghc_reset(struct vmbus_msghc *mh, size_t dsize)
 {
@@ -1382,6 +1391,9 @@ vmbus_doattach(struct vmbus_softc *sc)
 	struct sysctl_oid_list *child;
 	struct sysctl_ctx_list *ctx;
 	int ret;
+	device_t dev_res;
+	ACPI_HANDLE handle;
+	unsigned int coherent;
 
 	if (sc->vmbus_flags & VMBUS_FLAG_ATTACHED)
 		return (0);
@@ -1402,6 +1414,27 @@ vmbus_doattach(struct vmbus_softc *sc)
 	    sizeof(struct vmbus_channel *) * VMBUS_CHAN_MAX, M_DEVBUF,
 	    M_WAITOK | M_ZERO);
 
+	/* Coherency attribute */
+	dev_res =  devclass_get_device(devclass_find("vmbus_res"), 0);
+	handle = acpi_get_handle(dev_res);
+
+	if (ACPI_FAILURE(acpi_GetInteger(handle, "_CCA", &coherent)))
+		coherent = 0;
+	if (bootverbose)
+		device_printf(sc->vmbus_dev, "Bus is%s cache-coherent\n",
+			coherent ? "" : " not");
+
+	bus_dma_tag_create(bus_get_dma_tag(sc->vmbus_dev),
+		1, 0,
+		BUS_SPACE_MAXADDR,
+		BUS_SPACE_MAXADDR,
+		NULL, NULL,
+		BUS_SPACE_MAXSIZE,
+		BUS_SPACE_UNRESTRICTED,
+		BUS_SPACE_MAXSIZE,
+		coherent ? BUS_DMA_COHERENT : 0,
+		NULL, NULL,
+		&sc->dmat);
 	/*
 	 * Create context for "post message" Hypercalls
 	 */
diff --git a/sys/dev/hyperv/vmbus/vmbus_var.h b/sys/dev/hyperv/vmbus/vmbus_var.h
index f6fc875deb32..023d27c52cea 100644
--- a/sys/dev/hyperv/vmbus/vmbus_var.h
+++ b/sys/dev/hyperv/vmbus/vmbus_var.h
@@ -129,6 +129,7 @@ struct vmbus_softc {
 	void *icookie;
 	int vector;
 #endif
+	bus_dma_tag_t   dmat;
 };
 
 #define VMBUS_FLAG_ATTACHED	0x0001	/* vmbus was attached */