xen/arm: its: refactor ITS quirk matching

ITS quirks are matched only by IIDR and mask fields stored in each table
entry. That is too coarse when the same GIC IP block appears on several
platforms but a workaround is valid only for some of them.

Replace the fixed IIDR fields with a generic match(hw_its, data)
callback and an opaque data pointer. Add an IIDR matcher as a reusable
building block and use it from the R-Car Gen4 matcher after checking the
Renesas machine compatibles.

This intentionally narrows the R-Car Gen4 quirk. Previously every ITS
with IIDR 0x0201743b matched. Now it matches only a DT-discovered ITS on
an r8a779f0 or r8a779g0 machine. ACPI-discovered ITSes and the same IIDR
on other platforms no longer match.

Keep first-match semantics explicit. Use BUG_ON() if a non-sentinel
entry has no matcher or the IIDR matcher receives no data. A broken
entry must stop Xen in both debug and release builds, as skipping a
required workaround could cause a failure later. Place the matcher data
and table in init-only read-only sections.

The matched entry still supplies separate ITS and LPI flags; this patch
only changes how the entry is selected.

Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
Reviewed-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

xen/arch/arm/gic-v3-its.c

@@ -54,8 +54,8 @@ struct its_device {
 
 struct its_quirk {
     const char *desc;
-    uint32_t iidr;
-    uint32_t mask;
+    bool (*match)(const struct host_its *hw_its, const void *data);
+    const void *data;
     uint32_t its_flags;
     /*
      * lpi_flags are ORed into the global host LPI policy and must only
@@ -65,11 +65,49 @@ struct its_quirk {
     uint32_t lpi_flags;
 };
 
-static const struct its_quirk its_quirks[] = {
-    {
-        .desc	= "R-Car Gen4",
+struct its_quirk_match_iidr {
+    uint32_t iidr;
+    uint32_t mask;
+};
+
+static bool __init gicv3_its_match_iidr(const struct host_its *hw_its,
+                                        const void *data)
+{
+    const struct its_quirk_match_iidr *match;
+    uint32_t iidr;
+
+    BUG_ON(!data);
+
+    match = data;
+    iidr = readl_relaxed(hw_its->its_base + GITS_IIDR);
+
+    return (iidr & match->mask) == match->iidr;
+}
+
+static bool __init gicv3_its_match_quirk_gen4(const struct host_its *hw_its,
+                                              const void *data)
+{
+    if ( !hw_its->dt_node )
+        return false;
+
+    if ( !dt_machine_is_compatible("renesas,r8a779f0") &&
+         !dt_machine_is_compatible("renesas,r8a779g0") )
+        return false;
+
+    return gicv3_its_match_iidr(hw_its, data);
+}
+
+static const struct its_quirk_match_iidr rcar_gen4_iidr __initconst = {
+    /* Implementer 0x43b identifies Arm Ltd. */
     .iidr = 0x0201743b,
     .mask = 0xffffffffU,
+};
+
+static const struct its_quirk its_quirks[] __initconstrel = {
+    {
+        .desc = "R-Car Gen4",
+        .match = gicv3_its_match_quirk_gen4,
+        .data = &rcar_gen4_iidr,
         .its_flags = GICV3_QUIRK_MEM_NC_NS | GICV3_QUIRK_MEM_32BIT_ADDR,
         .lpi_flags = GICV3_QUIRK_MEM_NC_NS | GICV3_QUIRK_MEM_32BIT_ADDR,
     },
@@ -78,17 +116,20 @@ static const struct its_quirk its_quirks[] = {
     }
 };
 
-static const struct its_quirk *__init gicv3_its_find_quirk(uint32_t iidr)
+static const struct its_quirk *__init gicv3_its_find_quirk(
+    const struct host_its *hw_its)
 {
     const struct its_quirk *quirks = its_quirks;
 
     /*
-     * The first matching quirk wins. More specific quirks must be listed
-     * before broader IIDR-only entries.
+     * The first matching quirk wins. Entries that match a specific platform
+     * must be listed before broader IIDR-only entries.
      */
     for ( ; quirks->desc; quirks++ )
     {
-        if ( quirks->iidr == (quirks->mask & iidr) )
+        BUG_ON(!quirks->match);
+
+        if ( quirks->match(hw_its, quirks->data) )
             return quirks;
     }
 
@@ -97,8 +138,7 @@ static const struct its_quirk *__init gicv3_its_find_quirk(uint32_t iidr)
 
 static void __init gicv3_its_collect_quirks(struct host_its *hw_its)
 {
-    uint32_t iidr = readl_relaxed(hw_its->its_base + GITS_IIDR);
-    const struct its_quirk *quirk = gicv3_its_find_quirk(iidr);
+    const struct its_quirk *quirk = gicv3_its_find_quirk(hw_its);
 
     if ( quirk )
     {