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, 77 insertions, 0 deletions

diff --git a/arch/mips/bcm63xx/dev-uart.c b/arch/mips/bcm63xx/dev-uart.c
new file mode 100644
index 000000000..5d6bf0445
--- /dev/null
+++ b/arch/mips/bcm63xx/dev-uart.c
@@ -0,0 +1,77 @@
+/*
+ * 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/init.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <bcm63xx_cpu.h>
+#include <bcm63xx_dev_uart.h>
+
+static struct resource uart0_resources[] = {
+	{
+		/* start & end filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		/* start filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct resource uart1_resources[] = {
+	{
+		/* start & end filled at runtime */
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		/* start filled at runtime */
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct platform_device bcm63xx_uart_devices[] = {
+	{
+		.name		= "bcm63xx_uart",
+		.id		= 0,
+		.num_resources	= ARRAY_SIZE(uart0_resources),
+		.resource	= uart0_resources,
+	},
+
+	{
+		.name		= "bcm63xx_uart",
+		.id		= 1,
+		.num_resources	= ARRAY_SIZE(uart1_resources),
+		.resource	= uart1_resources,
+	}
+};
+
+int __init bcm63xx_uart_register(unsigned int id)
+{
+	if (id >= ARRAY_SIZE(bcm63xx_uart_devices))
+		return -ENODEV;
+
+	if (id == 1 && (!BCMCPU_IS_3368() && !BCMCPU_IS_6358() &&
+		!BCMCPU_IS_6368()))
+		return -ENODEV;
+
+	if (id == 0) {
+		uart0_resources[0].start = bcm63xx_regset_address(RSET_UART0);
+		uart0_resources[0].end = uart0_resources[0].start +
+			RSET_UART_SIZE - 1;
+		uart0_resources[1].start = bcm63xx_get_irq_number(IRQ_UART0);
+	}
+
+	if (id == 1) {
+		uart1_resources[0].start = bcm63xx_regset_address(RSET_UART1);
+		uart1_resources[0].end = uart1_resources[0].start +
+			RSET_UART_SIZE - 1;
+		uart1_resources[1].start = bcm63xx_get_irq_number(IRQ_UART1);
+	}
+
+	return platform_device_register(&bcm63xx_uart_devices[id]);
+}