ACPI: VIOT: Fix ACS setup

Currently acpi_viot_init() gets called after the pci
device has been scanned and pci_enable_acs() has been called.
So pci_request_acs() fails to be taken into account leading
to wrong single iommu group topologies when dealing with
multi-function root ports for instance.

We cannot simply move the acpi_viot_init() earlier, similarly
as the IORT init because the VIOT parsing relies on the pci
scan. However we can detect VIOT is present earlier and in
such a case, request ACS. Introduce a new acpi_viot_early_init()
routine that allows to call pci_request_acs() before the scan.

While at it, guard the call to pci_request_acs() with #ifdef
CONFIG_PCI.

Fixes: 3cf485540e7b ("ACPI: Add driver for the VIOT table")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Jin Liu <jinl@redhat.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 20 insertions, 6 deletions

diff --git a/drivers/acpi/viot.c b/drivers/acpi/viot.c
index d2256326c73a..647f11cf165d 100644
--- a/drivers/acpi/viot.c
+++ b/drivers/acpi/viot.c
@@ -249,6 +249,26 @@ err_free:
 }
 
 /**
+ * acpi_viot_early_init - Test the presence of VIOT and enable ACS
+ *
+ * If the VIOT does exist, ACS must be enabled. This cannot be
+ * done in acpi_viot_init() which is called after the bus scan
+ */
+void __init acpi_viot_early_init(void)
+{
+#ifdef CONFIG_PCI
+	acpi_status status;
+	struct acpi_table_header *hdr;
+
+	status = acpi_get_table(ACPI_SIG_VIOT, 0, &hdr);
+	if (ACPI_FAILURE(status))
+		return;
+	pci_request_acs();
+	acpi_put_table(hdr);
+#endif
+}
+
+/**
  * acpi_viot_init - Parse the VIOT table
  *
  * Parse the VIOT table, prepare the list of endpoints to be used during DMA
@@ -319,12 +339,6 @@ static int viot_pci_dev_iommu_init(struct pci_dev *pdev, u16 dev_id, void *data)
 			epid = ((domain_nr - ep->segment_start) << 16) +
 				dev_id - ep->bdf_start + ep->endpoint_id;
 
-			/*
-			 * If we found a PCI range managed by the viommu, we're
-			 * the one that has to request ACS.
-			 */
-			pci_request_acs();
-
 			return viot_dev_iommu_init(&pdev->dev, ep->viommu,
 						   epid);
 		}