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, 162 insertions, 0 deletions

diff --git a/arch/mips/lib/bitops.c b/arch/mips/lib/bitops.c
new file mode 100644
index 000000000..00aee98e9
--- /dev/null
+++ b/arch/mips/lib/bitops.c
@@ -0,0 +1,162 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 1994-1997, 99, 2000, 06, 07 Ralf Baechle (ralf@linux-mips.org)
+ * Copyright (c) 1999, 2000  Silicon Graphics, Inc.
+ */
+#include <linux/bitops.h>
+#include <linux/bits.h>
+#include <linux/irqflags.h>
+#include <linux/export.h>
+
+
+/**
+ * __mips_set_bit - Atomically set a bit in memory.  This is called by
+ * set_bit() if it cannot find a faster solution.
+ * @nr: the bit to set
+ * @addr: the address to start counting from
+ */
+void __mips_set_bit(unsigned long nr, volatile unsigned long *addr)
+{
+	volatile unsigned long *a = &addr[BIT_WORD(nr)];
+	unsigned int bit = nr % BITS_PER_LONG;
+	unsigned long mask;
+	unsigned long flags;
+
+	mask = 1UL << bit;
+	raw_local_irq_save(flags);
+	*a |= mask;
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL(__mips_set_bit);
+
+
+/**
+ * __mips_clear_bit - Clears a bit in memory.  This is called by clear_bit() if
+ * it cannot find a faster solution.
+ * @nr: Bit to clear
+ * @addr: Address to start counting from
+ */
+void __mips_clear_bit(unsigned long nr, volatile unsigned long *addr)
+{
+	volatile unsigned long *a = &addr[BIT_WORD(nr)];
+	unsigned int bit = nr % BITS_PER_LONG;
+	unsigned long mask;
+	unsigned long flags;
+
+	mask = 1UL << bit;
+	raw_local_irq_save(flags);
+	*a &= ~mask;
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL(__mips_clear_bit);
+
+
+/**
+ * __mips_change_bit - Toggle a bit in memory.	This is called by change_bit()
+ * if it cannot find a faster solution.
+ * @nr: Bit to change
+ * @addr: Address to start counting from
+ */
+void __mips_change_bit(unsigned long nr, volatile unsigned long *addr)
+{
+	volatile unsigned long *a = &addr[BIT_WORD(nr)];
+	unsigned int bit = nr % BITS_PER_LONG;
+	unsigned long mask;
+	unsigned long flags;
+
+	mask = 1UL << bit;
+	raw_local_irq_save(flags);
+	*a ^= mask;
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL(__mips_change_bit);
+
+
+/**
+ * __mips_test_and_set_bit_lock - Set a bit and return its old value.  This is
+ * called by test_and_set_bit_lock() if it cannot find a faster solution.
+ * @nr: Bit to set
+ * @addr: Address to count from
+ */
+int __mips_test_and_set_bit_lock(unsigned long nr,
+				 volatile unsigned long *addr)
+{
+	volatile unsigned long *a = &addr[BIT_WORD(nr)];
+	unsigned int bit = nr % BITS_PER_LONG;
+	unsigned long mask;
+	unsigned long flags;
+	int res;
+
+	mask = 1UL << bit;
+	raw_local_irq_save(flags);
+	res = (mask & *a) != 0;
+	*a |= mask;
+	raw_local_irq_restore(flags);
+	return res;
+}
+EXPORT_SYMBOL(__mips_test_and_set_bit_lock);
+
+
+/**
+ * __mips_test_and_clear_bit - Clear a bit and return its old value.  This is
+ * called by test_and_clear_bit() if it cannot find a faster solution.
+ * @nr: Bit to clear
+ * @addr: Address to count from
+ */
+int __mips_test_and_clear_bit(unsigned long nr, volatile unsigned long *addr)
+{
+	volatile unsigned long *a = &addr[BIT_WORD(nr)];
+	unsigned int bit = nr % BITS_PER_LONG;
+	unsigned long mask;
+	unsigned long flags;
+	int res;
+
+	mask = 1UL << bit;
+	raw_local_irq_save(flags);
+	res = (mask & *a) != 0;
+	*a &= ~mask;
+	raw_local_irq_restore(flags);
+	return res;
+}
+EXPORT_SYMBOL(__mips_test_and_clear_bit);
+
+
+/**
+ * __mips_test_and_change_bit - Change a bit and return its old value.	This is
+ * called by test_and_change_bit() if it cannot find a faster solution.
+ * @nr: Bit to change
+ * @addr: Address to count from
+ */
+int __mips_test_and_change_bit(unsigned long nr, volatile unsigned long *addr)
+{
+	volatile unsigned long *a = &addr[BIT_WORD(nr)];
+	unsigned int bit = nr % BITS_PER_LONG;
+	unsigned long mask;
+	unsigned long flags;
+	int res;
+
+	mask = 1UL << bit;
+	raw_local_irq_save(flags);
+	res = (mask & *a) != 0;
+	*a ^= mask;
+	raw_local_irq_restore(flags);
+	return res;
+}
+EXPORT_SYMBOL(__mips_test_and_change_bit);
+
+bool __mips_xor_is_negative_byte(unsigned long mask,
+		volatile unsigned long *addr)
+{
+	unsigned long flags;
+	unsigned long data;
+
+	raw_local_irq_save(flags);
+	data = *addr;
+	*addr = data ^ mask;
+	raw_local_irq_restore(flags);
+
+	return (data & BIT(7)) != 0;
+}