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, 24 insertions, 0 deletions

diff --git a/arch/powerpc/boot/microwatt.c b/arch/powerpc/boot/microwatt.c
new file mode 100644
index 000000000..ca9d83617
--- /dev/null
+++ b/arch/powerpc/boot/microwatt.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <stddef.h>
+#include "stdio.h"
+#include "types.h"
+#include "io.h"
+#include "ops.h"
+
+BSS_STACK(8192);
+
+void platform_init(unsigned long r3, unsigned long r4, unsigned long r5)
+{
+	unsigned long heapsize = 16*1024*1024 - (unsigned long)_end;
+
+	/*
+	 * Disable interrupts and turn off MSR_RI, since we'll
+	 * shortly be overwriting the interrupt vectors.
+	 */
+	__asm__ volatile("mtmsrd %0,1" : : "r" (0));
+
+	simple_alloc_init(_end, heapsize, 32, 64);
+	fdt_init(_dtb_start);
+	serial_console_init();
+}