KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 139 insertions, 0 deletions

diff --git a/arch/powerpc/boot/ps3.c b/arch/powerpc/boot/ps3.c
new file mode 100644
index 000000000..89ff46b8b
--- /dev/null
+++ b/arch/powerpc/boot/ps3.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  PS3 bootwrapper support.
+ *
+ *  Copyright (C) 2007 Sony Computer Entertainment Inc.
+ *  Copyright 2007 Sony Corp.
+ */
+
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "elf.h"
+#include "string.h"
+#include "stdio.h"
+#include "page.h"
+#include "ops.h"
+
+extern int lv1_panic(u64 in_1);
+extern int lv1_get_logical_partition_id(u64 *out_1);
+extern int lv1_get_logical_ppe_id(u64 *out_1);
+extern int lv1_get_repository_node_value(u64 in_1, u64 in_2, u64 in_3,
+	u64 in_4, u64 in_5, u64 *out_1, u64 *out_2);
+
+BSS_STACK(4096);
+
+/* A buffer that may be edited by tools operating on a zImage binary so as to
+ * edit the command line passed to vmlinux (by setting /chosen/bootargs).
+ * The buffer is put in its own section so that tools may locate it easier.
+ */
+
+static char cmdline[BOOT_COMMAND_LINE_SIZE]
+	__attribute__((__section__("__builtin_cmdline")));
+
+static void prep_cmdline(void *chosen)
+{
+	if (cmdline[0] == '\0')
+		getprop(chosen, "bootargs", cmdline, BOOT_COMMAND_LINE_SIZE-1);
+	else
+		setprop_str(chosen, "bootargs", cmdline);
+
+	printf("cmdline: '%s'\n", cmdline);
+}
+
+static void ps3_console_write(const char *buf, int len)
+{
+}
+
+static void ps3_exit(void)
+{
+	printf("ps3_exit\n");
+
+	/* lv1_panic will shutdown the lpar. */
+
+	lv1_panic(0); /* zero = do not reboot */
+	while (1);
+}
+
+static int ps3_repository_read_rm_size(u64 *rm_size)
+{
+	int result;
+	u64 lpar_id;
+	u64 ppe_id;
+	u64 v2;
+
+	result = lv1_get_logical_partition_id(&lpar_id);
+
+	if (result)
+		return -1;
+
+	result = lv1_get_logical_ppe_id(&ppe_id);
+
+	if (result)
+		return -1;
+
+	/*
+	 * n1: 0000000062690000 : ....bi..
+	 * n2: 7075000000000000 : pu......
+	 * n3: 0000000000000001 : ........
+	 * n4: 726d5f73697a6500 : rm_size.
+	*/
+
+	result = lv1_get_repository_node_value(lpar_id, 0x0000000062690000ULL,
+		0x7075000000000000ULL, ppe_id, 0x726d5f73697a6500ULL, rm_size,
+		&v2);
+
+	printf("%s:%d: ppe_id  %lu \n", __func__, __LINE__,
+		(unsigned long)ppe_id);
+	printf("%s:%d: lpar_id %lu \n", __func__, __LINE__,
+		(unsigned long)lpar_id);
+	printf("%s:%d: rm_size %llxh \n", __func__, __LINE__, *rm_size);
+
+	return result ? -1 : 0;
+}
+
+void ps3_copy_vectors(void)
+{
+	extern char __system_reset_kernel[];
+
+	memcpy((void *)0x100, __system_reset_kernel, 512);
+	flush_cache((void *)0x100, 512);
+}
+
+void platform_init(void)
+{
+	const u32 heapsize = 0x1000000 - (u32)_end; /* 16MiB */
+	void *chosen;
+	unsigned long ft_addr;
+	u64 rm_size;
+
+	console_ops.write = ps3_console_write;
+	platform_ops.exit = ps3_exit;
+
+	printf("\n-- PS3 bootwrapper --\n");
+
+	simple_alloc_init(_end, heapsize, 32, 64);
+	fdt_init(_dtb_start);
+
+	chosen = finddevice("/chosen");
+
+	ps3_repository_read_rm_size(&rm_size);
+	dt_fixup_memory(0, rm_size);
+
+	if (&_initrd_end > &_initrd_start) {
+		setprop_val(chosen, "linux,initrd-start", (u32)(_initrd_start));
+		setprop_val(chosen, "linux,initrd-end", (u32)(_initrd_end));
+	}
+
+	prep_cmdline(chosen);
+
+	ft_addr = dt_ops.finalize();
+
+	ps3_copy_vectors();
+
+	printf(" flat tree at 0x%lx\n\r", ft_addr);
+
+	((kernel_entry_t)0)(ft_addr, 0, NULL);
+
+	ps3_exit();
+}