From 3dcb861dbc6ab101838a1548b1efddd00ca3c3ec Mon Sep 17 00:00:00 2001
From: Eric Auger <eric.auger@redhat.com>
Date: Thu, 30 Jun 2022 11:40:59 +0200
Subject: [PATCH] ACPI: VIOT: Fix ACS setup
Git-commit: 3dcb861dbc6ab101838a1548b1efddd00ca3c3ec
Patch-mainline: v6.0-rc1
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/acpi/bus.c        |    1 +
 drivers/acpi/viot.c       |   26 ++++++++++++++++++++------
 include/linux/acpi_viot.h |    2 ++
 3 files changed, 23 insertions(+), 6 deletions(-)

--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -1353,6 +1353,7 @@ static int __init acpi_init(void)
 
 	pci_mmcfg_late_init();
 	acpi_iort_init();
+	acpi_viot_early_init();
 	acpi_hest_init();
 	acpi_ghes_init();
 	acpi_scan_init();
--- 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(struc
 			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);
 		}
--- a/include/linux/acpi_viot.h
+++ b/include/linux/acpi_viot.h
@@ -6,9 +6,11 @@
 #include <linux/acpi.h>
 
 #ifdef CONFIG_ACPI_VIOT
+void __init acpi_viot_early_init(void);
 void __init acpi_viot_init(void);
 int viot_iommu_configure(struct device *dev);
 #else
+static inline void acpi_viot_early_init(void) {}
 static inline void acpi_viot_init(void) {}
 static inline int viot_iommu_configure(struct device *dev)
 {