iommu/amd: Fix the overwritten field in IVMD header

Commit 387caf0b ("iommu/amd: Treat per-device exclusion
ranges as r/w unity-mapped regions") accidentally overwrites
the 'flags' field in IVMD (struct ivmd_header) when the I/O
virtualization memory definition is associated with the
exclusion range entry. This leads to the corrupted IVMD table
(incorrect checksum). The kdump kernel reports the invalid checksum:

ACPI BIOS Warning (bug): Incorrect checksum in table [IVRS] - 0x5C, should be 0x60 (20200717/tbprint-177)
AMD-Vi: [Firmware Bug]: IVRS invalid checksum

Fix the above-mentioned issue by modifying the 'struct unity_map_entry'
member instead of the IVMD header.

Cleanup: The *exclusion_range* functions are not used anymore, so
get rid of them.

Fixes: 387caf0b ("iommu/amd: Treat per-device exclusion ranges as r/w unity-mapped regions")
Reported-and-tested-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Adrian Huang <ahuang12@lenovo.com>
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Link: https://lore.kernel.org/r/20200926102602.19177-1-adrianhuang0701@gmail.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd/init.c

@@ -1103,25 +1103,6 @@ static int __init add_early_maps(void)
 	return 0;
 }
 
-/*
- * Reads the device exclusion range from ACPI and initializes the IOMMU with
- * it
- */
-static void __init set_device_exclusion_range(u16 devid, struct ivmd_header *m)
-{
-	if (!(m->flags & IVMD_FLAG_EXCL_RANGE))
-		return;
-
-	/*
-	 * Treat per-device exclusion ranges as r/w unity-mapped regions
-	 * since some buggy BIOSes might lead to the overwritten exclusion
-	 * range (exclusion_start and exclusion_length members). This
-	 * happens when there are multiple exclusion ranges (IVMD entries)
-	 * defined in ACPI table.
-	 */
-	m->flags = (IVMD_FLAG_IW | IVMD_FLAG_IR | IVMD_FLAG_UNITY_MAP);
-}
-
 /*
  * Takes a pointer to an AMD IOMMU entry in the ACPI table and
  * initializes the hardware and our data structures with it.
@@ -2073,30 +2054,6 @@ static void __init free_unity_maps(void)
 	}
 }
 
-/* called when we find an exclusion range definition in ACPI */
-static int __init init_exclusion_range(struct ivmd_header *m)
-{
-	int i;
-
-	switch (m->type) {
-	case ACPI_IVMD_TYPE:
-		set_device_exclusion_range(m->devid, m);
-		break;
-	case ACPI_IVMD_TYPE_ALL:
-		for (i = 0; i <= amd_iommu_last_bdf; ++i)
-			set_device_exclusion_range(i, m);
-		break;
-	case ACPI_IVMD_TYPE_RANGE:
-		for (i = m->devid; i <= m->aux; ++i)
-			set_device_exclusion_range(i, m);
-		break;
-	default:
-		break;
-	}
-
-	return 0;
-}
-
 /* called for unity map ACPI definition */
 static int __init init_unity_map_range(struct ivmd_header *m)
 {
@@ -2107,9 +2064,6 @@ static int __init init_unity_map_range(struct ivmd_header *m)
 	if (e == NULL)
 		return -ENOMEM;
 
-	if (m->flags & IVMD_FLAG_EXCL_RANGE)
-		init_exclusion_range(m);
-
 	switch (m->type) {
 	default:
 		kfree(e);
@@ -2133,6 +2087,16 @@ static int __init init_unity_map_range(struct ivmd_header *m)
 	e->address_end = e->address_start + PAGE_ALIGN(m->range_length);
 	e->prot = m->flags >> 1;
 
+	/*
+	 * Treat per-device exclusion ranges as r/w unity-mapped regions
+	 * since some buggy BIOSes might lead to the overwritten exclusion
+	 * range (exclusion_start and exclusion_length members). This
+	 * happens when there are multiple exclusion ranges (IVMD entries)
+	 * defined in ACPI table.
+	 */
+	if (m->flags & IVMD_FLAG_EXCL_RANGE)
+		e->prot = (IVMD_FLAG_IW | IVMD_FLAG_IR) >> 1;
+
 	DUMP_printk("%s devid_start: %02x:%02x.%x devid_end: %02x:%02x.%x"
 		    " range_start: %016llx range_end: %016llx flags: %x\n", s,
 		    PCI_BUS_NUM(e->devid_start), PCI_SLOT(e->devid_start),