qfw: Add a subcommand to decode the QEMU E820 data

Provide a simple command to display the memory map described by this
table.

Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/qfw.c

@@ -234,6 +234,19 @@ static int do_read(struct cmd_tbl *cmdtp, int flag, int argc,
 	return 0;
 }
 
+static int do_e820(struct cmd_tbl *cmdtp, int flag, int argc,
+		   char * const argv[])
+{
+	if (!IS_ENABLED(CONFIG_X86)) {
+		printf("Not supported on this architecture\n");
+		return CMD_RET_FAILURE;
+	}
+
+	cmd_qfw_e820(qfw_dev);
+
+	return 0;
+}
+
 static struct cmd_tbl fwcfg_commands[] = {
 	U_BOOT_CMD_MKENT(list, 0, 1, qemu_fwcfg_do_list, "", ""),
 	U_BOOT_CMD_MKENT(cpus, 0, 1, qemu_fwcfg_do_cpus, "", ""),
@@ -242,6 +255,7 @@ static struct cmd_tbl fwcfg_commands[] = {
 	U_BOOT_CMD_MKENT(table, 0, 1, do_table, "", ""),
 	U_BOOT_CMD_MKENT(arch, 0, 1, do_arch, "", ""),
 	U_BOOT_CMD_MKENT(read, 2, 1, do_read, "", ""),
+	U_BOOT_CMD_MKENT(e820, 0, 1, do_e820, "", ""),
 };
 
 static int do_qemu_fw(struct cmd_tbl *cmdtp, int flag, int argc,
@@ -278,4 +292,5 @@ U_BOOT_CMD(
 	"    - load <kernel addr> <initrd addr> : load kernel and initrd (if any), and setup for zboot\n"
 	"    - table                            : show /etc/table-loader\n"
 	"    - arch                             : show arch-specific data\n"
-	"    - read <addr> <filename>           : read a flle into memory");
+	"    - read <addr> <filename>           : read a flle into memory\n"
+	"    - e820                             : show QEMU e820 table");

cmd/x86/Makefile

@@ -3,6 +3,7 @@
 obj-$(CONFIG_CMD_CBSYSINFO) += cbsysinfo.o
 obj-y += cpuid.o msr.o mtrr.o
 obj-$(CONFIG_CMD_CBCMOS) += cbcmos.o
+obj-y += qfw_x86.o
 obj-$(CONFIG_CMD_EXCEPTION) += exception.o
 obj-$(CONFIG_USE_HOB) += hob.o
 obj-$(CONFIG_HAVE_FSP) += fsp.o

cmd/x86/qfw_x86.c

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * x86-specific qfw commands
+ *
+ * Copyright 2025 Simon Glass <sjg@chromium.org>
+ */
+
+#include <abuf.h>
+#include <command.h>
+#include <qfw.h>
+#include <asm/e820.h>
+
+int cmd_qfw_e820(struct udevice *dev)
+{
+	struct abuf tab;
+	int ret;
+
+	ret = qfw_get_file(dev, "etc/e820", &tab);
+	if (ret)
+		return CMD_RET_FAILURE;
+	e820_dump(tab.data, tab.size / sizeof(struct e820_entry));
+	abuf_uninit(&tab);
+
+	return 0;
+}

doc/usage/cmd/qfw.rst

@@ -18,6 +18,7 @@ Synopsis
     qfw table
     qfw arch
     qfw read <addr> <filename>
+    qfw e820
 
 Description
 -----------
@@ -40,6 +41,9 @@ The *qfw arch* command shows some items marked as 'arch local' in QEMU.
 
 The *qfw read* command allowing a QEMU file to be read into memory.
 
+The *qfw e820* command shows the memory-map information provided by QEMU. It
+uses the x86 e820 format.
+
 kernel_addr
     address to which the file specified by the -kernel parameter of QEMU shall
     be loaded. Defaults to environment variable *loadaddr* and further to
@@ -199,6 +203,18 @@ provided size information:
     00001010: 40 1c 00 00                                      @...
 
 
+This shows dumping the E820 table, showing the emulated RAM as well as some
+reserved memory:
+
+::
+
+    => qfw e820
+            Addr        Size  Type
+      fd00000000   300000000  Reserved
+               0    20000000  RAM
+    =>
+
+
 Configuration
 -------------
 

include/qfw.h

@@ -464,4 +464,12 @@ int qfw_load_file(struct udevice *dev, const char *fname, ulong addr);
  */
 int qfw_get_file(struct udevice *dev, const char *fname, struct abuf *loader);
 
+/**
+ * cmd_qfw_e820() - Execute the 'qfw e820' command for x86
+ *
+ * @dev: UCLASS_QFW device
+ * Return: 0 on success (always), 1 if there is no E820 information
+ */
+int cmd_qfw_e820(struct udevice *dev);
+
 #endif

test/cmd/qfw.c

@@ -113,3 +113,21 @@ static int cmd_test_qfw_read(struct unit_test_state *uts)
 	return 0;
 }
 CMD_TEST(cmd_test_qfw_read, UTF_CONSOLE);
+
+/* Test 'qfw e820' command */
+static int cmd_test_qfw_e820(struct unit_test_state *uts)
+{
+	int ret;
+
+	ret = run_command("qfw e820", 0);
+	if (!IS_ENABLED(CONFIG_X86)) {
+		ut_asserteq(1, ret);
+		return 0;
+	}
+
+	ut_assertok(ret);
+	ut_assert_nextline("        Addr        Size  Type");
+
+	return 0;
+}
+CMD_TEST(cmd_test_qfw_e820, UTF_CONSOLE);