@@ -19,6 +19,7 @@
#include <linux/cpumask.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
+#include <linux/dma-mapping.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
@@ -215,6 +216,16 @@ bool hv_query_ext_cap(u64 cap_query)
}
EXPORT_SYMBOL_GPL(hv_query_ext_cap);
+void hv_setup_dma_ops(struct device *dev, bool coherent)
+{
+ /*
+ * Hyper-V does not offer a vIOMMU in the guest
+ * VM, so pass 0/NULL for the IOMMU settings
+ */
+ arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
+}
+EXPORT_SYMBOL_GPL(hv_setup_dma_ops);
+
bool hv_is_hibernation_supported(void)
{
return !hv_root_partition && acpi_sleep_state_supported(ACPI_STATE_S4);
@@ -911,6 +911,21 @@ static int vmbus_probe(struct device *child_device)
return ret;
}
+/*
+ * vmbus_dma_configure -- Configure DMA coherence for VMbus device
+ */
+static int vmbus_dma_configure(struct device *child_device)
+{
+ /*
+ * On ARM64, propagate the DMA coherence setting from the top level
+ * VMbus ACPI device to the child VMbus device being added here.
+ * On x86/x64 coherence is assumed and these calls have no effect.
+ */
+ hv_setup_dma_ops(child_device,
+ device_get_dma_attr(&hv_acpi_dev->dev) == DEV_DMA_COHERENT);
+ return 0;
+}
+
/*
* vmbus_remove - Remove a vmbus device
*/
@@ -1032,6 +1047,7 @@ static struct bus_type hv_bus = {
.remove = vmbus_remove,
.probe = vmbus_probe,
.uevent = vmbus_uevent,
+ .dma_configure = vmbus_dma_configure,
.dev_groups = vmbus_dev_groups,
.drv_groups = vmbus_drv_groups,
.pm = &vmbus_pm,
@@ -2400,6 +2416,21 @@ static int vmbus_acpi_add(struct acpi_device *device)
hv_acpi_dev = device;
+ /*
+ * Older versions of Hyper-V for ARM64 fail to include the _CCA
+ * method on the top level VMbus device in the DSDT. But devices
+ * are hardware coherent in all current Hyper-V use cases, so fix
+ * up the ACPI device to behave as if _CCA is present and indicates
+ * hardware coherence.
+ */
+ ACPI_COMPANION_SET(&device->dev, device);
+ if (IS_ENABLED(CONFIG_ACPI_CCA_REQUIRED) &&
+ device_get_dma_attr(&device->dev) == DEV_DMA_NOT_SUPPORTED) {
+ pr_info("No ACPI _CCA found; assuming coherent device I/O\n");
+ device->flags.cca_seen = true;
+ device->flags.coherent_dma = true;
+ }
+
result = acpi_walk_resources(device->handle, METHOD_NAME__CRS,
vmbus_walk_resources, NULL);
@@ -202,6 +202,7 @@ void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
bool hv_is_hyperv_initialized(void);
bool hv_is_hibernation_supported(void);
void hyperv_cleanup(void);
+void hv_setup_dma_ops(struct device *dev, bool coherent);
#else /* CONFIG_HYPERV */
static inline bool hv_is_hyperv_initialized(void) { return false; }
static inline bool hv_is_hibernation_supported(void) { return false; }