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, 103 insertions, 0 deletions

diff --git a/arch/powerpc/boot/io.h b/arch/powerpc/boot/io.h
new file mode 100644
index 000000000..5c6f90c34
--- /dev/null
+++ b/arch/powerpc/boot/io.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _IO_H
+#define _IO_H
+
+#include "types.h"
+
+/*
+ * Low-level I/O routines.
+ *
+ * Copied from <file:arch/powerpc/include/asm/io.h> (which has no copyright)
+ */
+static inline int in_8(const volatile unsigned char *addr)
+{
+	int ret;
+
+	__asm__ __volatile__("lbz%U1%X1 %0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "m" (*addr));
+	return ret;
+}
+
+static inline void out_8(volatile unsigned char *addr, int val)
+{
+	__asm__ __volatile__("stb%U0%X0 %1,%0; sync"
+			     : "=m" (*addr) : "r" (val));
+}
+
+static inline unsigned in_le16(const volatile u16 *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lhbrx %0,0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "r" (addr), "m" (*addr));
+
+	return ret;
+}
+
+static inline unsigned in_be16(const volatile u16 *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lhz%U1%X1 %0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "m" (*addr));
+	return ret;
+}
+
+static inline void out_le16(volatile u16 *addr, int val)
+{
+	__asm__ __volatile__("sthbrx %1,0,%2; sync" : "=m" (*addr)
+			     : "r" (val), "r" (addr));
+}
+
+static inline void out_be16(volatile u16 *addr, int val)
+{
+	__asm__ __volatile__("sth%U0%X0 %1,%0; sync"
+			     : "=m" (*addr) : "r" (val));
+}
+
+static inline unsigned in_le32(const volatile unsigned *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lwbrx %0,0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "r" (addr), "m" (*addr));
+	return ret;
+}
+
+static inline unsigned in_be32(const volatile unsigned *addr)
+{
+	unsigned ret;
+
+	__asm__ __volatile__("lwz%U1%X1 %0,%1; twi 0,%0,0; isync"
+			     : "=r" (ret) : "m" (*addr));
+	return ret;
+}
+
+static inline void out_le32(volatile unsigned *addr, int val)
+{
+	__asm__ __volatile__("stwbrx %1,0,%2; sync" : "=m" (*addr)
+			     : "r" (val), "r" (addr));
+}
+
+static inline void out_be32(volatile unsigned *addr, int val)
+{
+	__asm__ __volatile__("stw%U0%X0 %1,%0; sync"
+			     : "=m" (*addr) : "r" (val));
+}
+
+static inline void sync(void)
+{
+	asm volatile("sync" : : : "memory");
+}
+
+static inline void eieio(void)
+{
+	asm volatile("eieio" : : : "memory");
+}
+
+static inline void barrier(void)
+{
+	asm volatile("" : : : "memory");
+}
+
+#endif /* _IO_H */