From c22ddc4368650550845f862fc07cb35b998fbb23 Mon Sep 17 00:00:00 2001
From: Gavin Shan <gshan@redhat.com>
Date: Wed, 9 Sep 2026 19:58:37 +1000
Subject: [PATCH] plat/qemu: add plat_rmmd_reserve_memory() for VIRT platform
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Signed-off-by: Gavin Shan <gshan@redhat.com>
---
 plat/qemu/qemu/include/platform_def.h  |  3 +++
 plat/qemu/qemu/plat_rmm_mem_carveout.c | 28 ++++++++++++++++++++++++++
 plat/qemu/qemu/platform.mk             |  4 ++++
 3 files changed, 35 insertions(+)
 create mode 100644 plat/qemu/qemu/plat_rmm_mem_carveout.c

diff --git a/plat/qemu/qemu/include/platform_def.h b/plat/qemu/qemu/include/platform_def.h
index 06018e7b2..c3ed986cf 100644
--- a/plat/qemu/qemu/include/platform_def.h
+++ b/plat/qemu/qemu/include/platform_def.h
@@ -368,6 +368,9 @@ CASSERT((PLAT_QEMU_L0_GPT_BASE & (PLAT_QEMU_L0_GPT_SIZE - 1)) == 0,
 #define RMM_SHARED_BASE			(RMM_LIMIT)
 #define RMM_SHARED_SIZE			PLAT_QEMU_RMM_SHARED_SIZE
 
+#define PLAT_ARM_RMM_PAYLOAD_SIZE	UL(0x600000)    /* 2 * 3MB */
+#define RMM_PAYLOAD_LIMIT		(RMM_BASE + PLAT_ARM_RMM_PAYLOAD_SIZE)
+
 /*
  * We add the RMM_SHARED size to RMM mapping to map the region as a block.
  * Else we end up requiring more pagetables in BL2 for ROMLIB build.
diff --git a/plat/qemu/qemu/plat_rmm_mem_carveout.c b/plat/qemu/qemu/plat_rmm_mem_carveout.c
new file mode 100644
index 000000000..c68ca243d
--- /dev/null
+++ b/plat/qemu/qemu/plat_rmm_mem_carveout.c
@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2026, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <lib/spinlock.h>
+#include <plat/common/platform.h>
+
+static spinlock_t mem_reserve_lock;
+static uintptr_t top_mem = RMM_LIMIT;
+
+uintptr_t plat_rmmd_reserve_memory(size_t size, unsigned long alignment)
+{
+	uint64_t align_mask = alignment - 1;
+	uintptr_t addr;
+
+	spin_lock(&mem_reserve_lock);
+	addr = (top_mem - size) & ~align_mask;
+	if (addr >= RMM_PAYLOAD_LIMIT) {
+		top_mem = addr;
+	} else {
+		addr = 0;
+	}
+	spin_unlock(&mem_reserve_lock);
+
+	return addr;
+}
diff --git a/plat/qemu/qemu/platform.mk b/plat/qemu/qemu/platform.mk
index 2e12f6bca..655cc683a 100644
--- a/plat/qemu/qemu/platform.mk
+++ b/plat/qemu/qemu/platform.mk
@@ -175,6 +175,10 @@ BL31_SOURCES		+=	plat/common/plat_spmd_manifest.c	\
 				${FDT_WRAPPERS_SOURCES}
 endif
 
+ifeq (${ENABLE_RMM},1)
+BL31_SOURCES		+=	${PLAT_QEMU_PATH}/plat_rmm_mem_carveout.c
+endif
+
 ifneq (${ENABLE_FEAT_RNG_TRAP},0)
 BL31_SOURCES		+=	plat/qemu/qemu/qemu_sync_traps.c
 endif
-- 
2.55.0