[PATCH v1] acpi/arm: relax MADT GICC entry length check to support newer ACPI revisions

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Newer ACPI revisions define the MADT GICC entry with Length = 82 bytes [1].
The current BAD_MADT_GICC_ENTRY() check rejects entries whose length does not
match the known values, which leads to:
  GICv3: No valid GICC entries exist.
as observed on the AmpereOne platform.

To fix this, import the logic from import from Linux commit 9eb1c92:
  The BAD_MADT_GICC_ENTRY check is a little too strict because
  it rejects MADT entries that don't match the currently known
  lengths. We should remove this restriction to avoid problems
  if the table length changes. Future code which might depend on
  additional fields should be written to validate those fields
  before using them, rather than trying to globally check
  known MADT version lengths.

  Link: https://lkml.kernel.org/r/20181012192937.3819951-1-jeremy.linton@xxxxxxx
  Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
  [lorenzo.pieralisi@xxxxxxx: added MADT macro comments]
  Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
  Acked-by: Sudeep Holla <sudeep.holla@xxxxxxx>
  Cc: Will Deacon <will.deacon@xxxxxxx>
  Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
  Cc: Al Stone <ahs3@xxxxxxxxxx>
  Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
  Signed-off-by: Will Deacon <will.deacon@xxxxxxx>

As ACPI_MADT_GICC_LENGTH is dropped, update the functions where it is
used. As we rewrite the MADT for hwdom, reuse the host GICC header length
instead of ACPI_MADT_GICC_LENGTH.

[1] 
https://uefi.org/specs/ACPI/6.6/05_ACPI_Software_Programming_Model.html#gic-cpu-interface-gicc-structure

Reported-By: Yann Dirson <yann.dirson@xxxxxxxxxx>
Co-developed-by: Yann Sionneau <yann.sionneau@xxxxxxxxxx>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
I ran CI tests where it made sense for this patch, as I don’t see any CI job
that builds Xen with CONFIG_ACPI=y:
  https://gitlab.com/xen-project/people/olkur/xen/-/pipelines/2222160666

I also built Xen manually with CONFIG_ACPI=y enabled and tested it on the
AmpereOne platform.
---
 xen/arch/arm/gic-v2.c           |  3 ++-
 xen/arch/arm/gic-v3.c           |  3 ++-
 xen/arch/arm/gic.c              | 12 +++++++++++-
 xen/arch/arm/include/asm/acpi.h | 21 +++++++++++++++------
 4 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
index b23e72a3d0..aae6a7bf30 100644
--- a/xen/arch/arm/gic-v2.c
+++ b/xen/arch/arm/gic-v2.c
@@ -1121,7 +1121,8 @@ static int gicv2_make_hwdom_madt(const struct domain *d, 
u32 offset)
     host_gicc = container_of(header, struct acpi_madt_generic_interrupt,
                              header);
 
-    size = ACPI_MADT_GICC_LENGTH;
+    size = host_gicc->header.length;
+
     /* Add Generic Interrupt */
     for ( i = 0; i < d->max_vcpus; i++ )
     {
diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
index bc07f97c16..75b89efad4 100644
--- a/xen/arch/arm/gic-v3.c
+++ b/xen/arch/arm/gic-v3.c
@@ -1672,7 +1672,8 @@ static int gicv3_make_hwdom_madt(const struct domain *d, 
u32 offset)
 
     host_gicc = container_of(header, struct acpi_madt_generic_interrupt,
                              header);
-    size = ACPI_MADT_GICC_LENGTH;
+    size = host_gicc->header.length;
+
     for ( i = 0; i < d->max_vcpus; i++ )
     {
         gicc = (struct acpi_madt_generic_interrupt *)(base_ptr + table_len);
diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index ee75258fc3..a0ccda14bf 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -418,8 +418,18 @@ unsigned long gic_get_hwdom_madt_size(const struct domain 
*d)
 {
     unsigned long madt_size;
 
+    struct acpi_subtable_header *header;
+    struct acpi_madt_generic_interrupt *host_gicc;
+
+    header = acpi_table_get_entry_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT, 0);
+    if ( !header )
+        panic("Can't get GICC entry");
+
+    host_gicc = container_of(header, struct acpi_madt_generic_interrupt,
+                             header);
+
     madt_size = sizeof(struct acpi_table_madt)
-                + ACPI_MADT_GICC_LENGTH * d->max_vcpus
+                + host_gicc->header.length * d->max_vcpus
                 + sizeof(struct acpi_madt_generic_distributor)
                 + gic_hw_ops->get_hwdom_extra_madt_size(d);
 
diff --git a/xen/arch/arm/include/asm/acpi.h b/xen/arch/arm/include/asm/acpi.h
index 13756dd341..30bc446d1f 100644
--- a/xen/arch/arm/include/asm/acpi.h
+++ b/xen/arch/arm/include/asm/acpi.h
@@ -53,13 +53,22 @@ void acpi_smp_init_cpus(void);
  */
 paddr_t acpi_get_table_offset(struct membank tbl_add[], EFI_MEM_RES index);
 
-/* Macros for consistency checks of the GICC subtable of MADT */
-#define ACPI_MADT_GICC_LENGTH  \
-    (acpi_gbl_FADT.header.revision < 6 ? 76 : 80)
+/*
+ * MADT GICC minimum length refers to the MADT GICC structure table length as
+ * defined in the earliest ACPI version supported on arm64, ie ACPI 5.1.
+ *
+ * The efficiency_class member was added to the
+ * struct acpi_madt_generic_interrupt to represent the MADT GICC structure
+ * "Processor Power Efficiency Class" field, added in ACPI 6.0 whose offset
+ * is therefore used to delimit the MADT GICC structure minimum length
+ * appropriately.
+ */
+#define ACPI_MADT_GICC_MIN_LENGTH   ACPI_OFFSET( \
+    struct acpi_madt_generic_interrupt, efficiency_class)
 
-#define BAD_MADT_GICC_ENTRY(entry, end)                                        
        \
-    (!(entry) || (unsigned long)(entry) + sizeof(*(entry)) > (end) ||  \
-     (entry)->header.length != ACPI_MADT_GICC_LENGTH)
+#define BAD_MADT_GICC_ENTRY(entry, end) \
+    (!(entry) || (entry)->header.length < ACPI_MADT_GICC_MIN_LENGTH || \
+    (unsigned long)(entry) + (entry)->header.length > (end))
 
 #ifdef CONFIG_ACPI
 extern bool acpi_disabled;
-- 
2.52.0