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, 145 insertions, 0 deletions

diff --git a/arch/mips/bcm63xx/cs.c b/arch/mips/bcm63xx/cs.c
new file mode 100644
index 000000000..29205badc
--- /dev/null
+++ b/arch/mips/bcm63xx/cs.c
@@ -0,0 +1,145 @@
+/*
+ * 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) 2008 Maxime Bizon <mbizon@freebox.fr>
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/spinlock.h>
+#include <linux/log2.h>
+#include <bcm63xx_cpu.h>
+#include <bcm63xx_io.h>
+#include <bcm63xx_regs.h>
+#include <bcm63xx_cs.h>
+
+static DEFINE_SPINLOCK(bcm63xx_cs_lock);
+
+/*
+ * check if given chip select exists
+ */
+static int is_valid_cs(unsigned int cs)
+{
+	if (cs > 6)
+		return 0;
+	return 1;
+}
+
+/*
+ * Configure chipselect base address and size (bytes).
+ * Size must be a power of two between 8k and 256M.
+ */
+int bcm63xx_set_cs_base(unsigned int cs, u32 base, unsigned int size)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	/* sanity check on size */
+	if (size != roundup_pow_of_two(size))
+		return -EINVAL;
+
+	if (size < 8 * 1024 || size > 256 * 1024 * 1024)
+		return -EINVAL;
+
+	val = (base & MPI_CSBASE_BASE_MASK);
+	/* 8k => 0 - 256M => 15 */
+	val |= (ilog2(size) - ilog2(8 * 1024)) << MPI_CSBASE_SIZE_SHIFT;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	bcm_mpi_writel(val, MPI_CSBASE_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_base);
+
+/*
+ * configure chipselect timing (ns)
+ */
+int bcm63xx_set_cs_timing(unsigned int cs, unsigned int wait,
+			   unsigned int setup, unsigned int hold)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	val &= ~(MPI_CSCTL_WAIT_MASK);
+	val &= ~(MPI_CSCTL_SETUP_MASK);
+	val &= ~(MPI_CSCTL_HOLD_MASK);
+	val |= wait << MPI_CSCTL_WAIT_SHIFT;
+	val |= setup << MPI_CSCTL_SETUP_SHIFT;
+	val |= hold << MPI_CSCTL_HOLD_SHIFT;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_timing);
+
+/*
+ * configure other chipselect parameter (data bus size, ...)
+ */
+int bcm63xx_set_cs_param(unsigned int cs, u32 params)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	/* none of this fields apply to pcmcia */
+	if (cs == MPI_CS_PCMCIA_COMMON ||
+	    cs == MPI_CS_PCMCIA_ATTR ||
+	    cs == MPI_CS_PCMCIA_IO)
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	val &= ~(MPI_CSCTL_DATA16_MASK);
+	val &= ~(MPI_CSCTL_SYNCMODE_MASK);
+	val &= ~(MPI_CSCTL_TSIZE_MASK);
+	val &= ~(MPI_CSCTL_ENDIANSWAP_MASK);
+	val |= params;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_param);
+
+/*
+ * set cs status (enable/disable)
+ */
+int bcm63xx_set_cs_status(unsigned int cs, int enable)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	if (enable)
+		val |= MPI_CSCTL_ENABLE_MASK;
+	else
+		val &= ~MPI_CSCTL_ENABLE_MASK;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_status);