[xen staging] xen/arm: its: handle dma-noncoherent on GIC and ITS nodes

[patchbot@xxxxxxx]

commit 17096ed1e46bfd82638264789a9110400c502210
Author:     Mykola Kvach <mykola_kvach@xxxxxxxx>
AuthorDate: Tue Sep 29 22:02:13 2026 +0300
Commit:     Michal Orzel <michal.orzel@xxxxxxx>
CommitDate: Mon Oct 26 09:01:40 2026 +0100

    xen/arm: its: handle dma-noncoherent on GIC and ITS nodes
    
    The DT dma-noncoherent property describes the bus coherency of the
    device represented by the node. On an ITS subnode, that is memory
    accessed by that ITS. Add GICV3_QUIRK_MEM_NC_NS to the corresponding
    host_its and use it when programming GITS_CBASER and GITS_BASER<n>.
    
    On the top-level GIC node, the property describes the Redistributor side
    of the LPI path. Collect it in gicv3_lpi_init_host_lpis() and apply it
    only to the host LPI policy used when allocating the property and
    pending tables and when programming GICR_PROPBASER and GICR_PENDBASER.
    Mark the function init-only because firmware attributes are collected
    only during boot.
    
    Do not inherit the property between parent and child nodes: ITS-node
    non-coherency does not change the global host LPI policy, and GIC-node
    non-coherency does not change per-ITS quirk_flags.
    
    ACPI is unchanged; this patch only consumes the DT dma-noncoherent
    property.
    
    Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
    Reviewed-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
    Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
---
 xen/arch/arm/gic-v3-its.c | 17 +++++++++++++++++
 xen/arch/arm/gic-v3-lpi.c | 20 +++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/gic-v3-its.c b/xen/arch/arm/gic-v3-its.c
index 43804a6c7a..f44ee21293 100644
--- a/xen/arch/arm/gic-v3-its.c
+++ b/xen/arch/arm/gic-v3-its.c
@@ -136,6 +136,21 @@ static const struct its_quirk *__init gicv3_its_find_quirk(
     return NULL;
 }
 
+static void __init gicv3_its_collect_fw_attrs(struct host_its *hw_its)
+{
+    /*
+     * An ITS subnode property describes memory transactions made by that ITS.
+     * Do not inherit it into the global host LPI/Redistributor policy.
+     */
+    if ( !hw_its->dt_node ||
+         !dt_property_read_bool(hw_its->dt_node, "dma-noncoherent") )
+        return;
+
+    hw_its->quirk_flags |= GICV3_QUIRK_MEM_NC_NS;
+    printk("GICv3: ITS @%#"PRIpaddr" marked dma-noncoherent\n",
+           hw_its->addr);
+}
+
 static void __init gicv3_its_collect_quirks(struct host_its *hw_its)
 {
     const struct its_quirk *quirk = gicv3_its_find_quirk(hw_its);
@@ -146,6 +161,8 @@ static void __init gicv3_its_collect_quirks(struct host_its 
*hw_its)
         gicv3_lpi_update_host_flags(quirk->lpi_flags);
         printk("GICv3: enabling workaround for ITS: %s\n", quirk->desc);
     }
+
+    gicv3_its_collect_fw_attrs(hw_its);
 }
 
 uint64_t gicv3_mem_get_cacheability(uint32_t flags)
diff --git a/xen/arch/arm/gic-v3-lpi.c b/xen/arch/arm/gic-v3-lpi.c
index accfd48a74..1cf49430ea 100644
--- a/xen/arch/arm/gic-v3-lpi.c
+++ b/xen/arch/arm/gic-v3-lpi.c
@@ -7,7 +7,9 @@
  * Copyright (C) 2016,2017 - ARM Ltd
  */
 
+#include <xen/acpi.h>
 #include <xen/cpu.h>
+#include <xen/device_tree.h>
 #include <xen/init.h>
 #include <xen/lib.h>
 #include <xen/mm.h>
@@ -102,6 +104,20 @@ void __init gicv3_lpi_update_host_flags(uint32_t flags)
     host_lpi_flags |= flags;
 }
 
+static void __init gicv3_lpi_collect_fw_attrs(void)
+{
+    /*
+     * A top-level GIC node property describes the Redistributor side of the
+     * LPI path. Do not inherit it into per-ITS policy.
+     */
+    if ( !acpi_disabled ||
+         !dt_property_read_bool(dt_interrupt_controller, "dma-noncoherent") )
+        return;
+
+    gicv3_lpi_update_host_flags(GICV3_QUIRK_MEM_NC_NS);
+    printk("GICv3: Redistributors marked dma-noncoherent\n");
+}
+
 static union host_lpi *gic_get_host_lpi(uint32_t plpi)
 {
     union host_lpi *block;
@@ -443,7 +459,7 @@ integer_param("max_lpi_bits", max_lpi_bits);
  * to the page with the actual "union host_lpi" entries. Our LPI limit
  * avoids excessive memory usage.
  */
-int gicv3_lpi_init_host_lpis(unsigned int host_lpi_bits)
+int __init gicv3_lpi_init_host_lpis(unsigned int host_lpi_bits)
 {
     unsigned int nr_lpi_ptrs;
     int rc;
@@ -451,6 +467,8 @@ int gicv3_lpi_init_host_lpis(unsigned int host_lpi_bits)
     /* We rely on the data structure being atomically accessible. */
     BUILD_BUG_ON(sizeof(union host_lpi) > sizeof(unsigned long));
 
+    gicv3_lpi_collect_fw_attrs();
+
     /*
      * An implementation needs to support at least 14 bits of LPI IDs.
      * Tell the user about it, the actual number is reported below.
--
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