AMD/IOMMU: obtain IVHD type to use earlier

Doing this in amd_iommu_prepare() is too late for it, in particular, to
be used in amd_iommu_detect_one_acpi(), as a subsequent change will want
to do. Moving it immediately ahead of amd_iommu_detect_acpi() is
(luckily) pretty simple, (pretty importantly) without breaking
amd_iommu_prepare()'s logic to prevent multiple processing.

This involves moving table checksumming, as
amd_iommu_get_supported_ivhd_type() ->  get_supported_ivhd_type() will
now be invoked before amd_iommu_detect_acpi()  -> detect_iommu_acpi(). In
the course of doing so stop open-coding acpi_tb_checksum(), seeing that
we have other uses of this originally ACPI-private function elsewhere in
the tree.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul@xen.org>

xen/drivers/passthrough/amd/iommu_acpi.c

@@ -22,6 +22,8 @@
 
 #include <asm/io_apic.h>
 
+#include <acpi/actables.h>
+
 #include "iommu.h"
 
 /* Some helper structures, particularly to deal with ranges. */
@@ -1167,20 +1169,7 @@ static int __init parse_ivrs_table(struct acpi_table_header *table)
 static int __init detect_iommu_acpi(struct acpi_table_header *table)
 {
     const struct acpi_ivrs_header *ivrs_block;
-    unsigned long i;
     unsigned long length = sizeof(struct acpi_table_ivrs);
-    u8 checksum, *raw_table;
-
-    /* validate checksum: sum of entire table == 0 */
-    checksum = 0;
-    raw_table = (u8 *)table;
-    for ( i = 0; i < table->length; i++ )
-        checksum += raw_table[i];
-    if ( checksum )
-    {
-        AMD_IOMMU_DEBUG("IVRS Error: Invalid Checksum %#x\n", checksum);
-        return -ENODEV;
-    }
 
     while ( table->length > (length + sizeof(*ivrs_block)) )
     {
@@ -1317,6 +1306,15 @@ get_supported_ivhd_type(struct acpi_table_header *table)
 {
     size_t length = sizeof(struct acpi_table_ivrs);
     const struct acpi_ivrs_header *ivrs_block, *blk = NULL;
+    uint8_t checksum;
+
+    /* Validate checksum: Sum of entire table == 0. */
+    checksum = acpi_tb_checksum(ACPI_CAST_PTR(uint8_t, table), table->length);
+    if ( checksum )
+    {
+        AMD_IOMMU_DEBUG("IVRS Error: Invalid Checksum %#x\n", checksum);
+        return -ENODEV;
+    }
 
     while ( table->length > (length + sizeof(*ivrs_block)) )
     {

xen/drivers/passthrough/amd/iommu_init.c

@@ -1398,15 +1398,9 @@ int __init amd_iommu_prepare(bool xt)
         goto error_out;
 
     /* Have we been here before? */
-    if ( ivhd_type )
+    if ( ivrs_bdf_entries )
         return 0;
 
-    rc = amd_iommu_get_supported_ivhd_type();
-    if ( rc < 0 )
-        goto error_out;
-    BUG_ON(!rc);
-    ivhd_type = rc;
-
     rc = amd_iommu_get_ivrs_dev_entries();
     if ( !rc )
         rc = -ENODEV;

xen/drivers/passthrough/amd/pci_amd_iommu.c

@@ -179,9 +179,17 @@ static int __must_check amd_iommu_setup_domain_device(
 
 int __init acpi_ivrs_init(void)
 {
+    int rc;
+
     if ( !iommu_enable && !iommu_intremap )
         return 0;
 
+    rc = amd_iommu_get_supported_ivhd_type();
+    if ( rc < 0 )
+        return rc;
+    BUG_ON(!rc);
+    ivhd_type = rc;
+
     if ( (amd_iommu_detect_acpi() !=0) || (iommu_found() == 0) )
     {
         iommu_intremap = iommu_intremap_off;