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, 154 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/nettel.c b/arch/m68k/coldfire/nettel.c
new file mode 100644
index 000000000..e304571e0
--- /dev/null
+++ b/arch/m68k/coldfire/nettel.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0
+/***************************************************************************/
+
+/*
+ *	nettel.c -- startup code support for the NETtel boards
+ *
+ *	Copyright (C) 2009, Greg Ungerer (gerg@snapgear.com)
+ */
+
+/***************************************************************************/
+
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+#include <asm/nettel.h>
+
+/***************************************************************************/
+
+/*
+ * Define the IO and interrupt resources of the 2 SMC9196 interfaces.
+ */
+#define	NETTEL_SMC0_ADDR	0x30600300
+#define	NETTEL_SMC0_IRQ		29
+
+#define	NETTEL_SMC1_ADDR	0x30600000
+#define	NETTEL_SMC1_IRQ		27
+
+/*
+ * We need some access into the SMC9196 registers. Define those registers
+ * we will need here (including the smc91x.h doesn't seem to give us these
+ * in a simple form).
+ */
+#define	SMC91xx_BANKSELECT	14
+#define	SMC91xx_BASEADDR	2
+#define	SMC91xx_BASEMAC		4
+
+/***************************************************************************/
+
+static struct resource nettel_smc91x_0_resources[] = {
+	{
+		.start		= NETTEL_SMC0_ADDR,
+		.end		= NETTEL_SMC0_ADDR + 0x20,
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= NETTEL_SMC0_IRQ,
+		.end		= NETTEL_SMC0_IRQ,
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct resource nettel_smc91x_1_resources[] = {
+	{
+		.start		= NETTEL_SMC1_ADDR,
+		.end		= NETTEL_SMC1_ADDR + 0x20,
+		.flags		= IORESOURCE_MEM,
+	},
+	{
+		.start		= NETTEL_SMC1_IRQ,
+		.end		= NETTEL_SMC1_IRQ,
+		.flags		= IORESOURCE_IRQ,
+	},
+};
+
+static struct platform_device nettel_smc91x[] = {
+	{
+		.name			= "smc91x",
+		.id			= 0,
+		.num_resources		= ARRAY_SIZE(nettel_smc91x_0_resources),
+		.resource		= nettel_smc91x_0_resources,
+	},
+	{
+		.name			= "smc91x",
+		.id			= 1,
+		.num_resources		= ARRAY_SIZE(nettel_smc91x_1_resources),
+		.resource		= nettel_smc91x_1_resources,
+	},
+};
+
+static struct platform_device *nettel_devices[] __initdata = {
+	&nettel_smc91x[0],
+	&nettel_smc91x[1],
+};
+
+/***************************************************************************/
+
+static u8 nettel_macdefault[] __initdata = {
+	0x00, 0xd0, 0xcf, 0x00, 0x00, 0x01,
+};
+
+/*
+ * Set flash contained MAC address into SMC9196 core. Make sure the flash
+ * MAC address is sane, and not an empty flash. If no good use the Moreton
+ * Bay default MAC address instead.
+ */
+
+static void __init nettel_smc91x_setmac(unsigned int ioaddr, unsigned int flashaddr)
+{
+	u16 *macp;
+
+	macp = (u16 *) flashaddr;
+	if ((macp[0] == 0xffff) && (macp[1] == 0xffff) && (macp[2] == 0xffff))
+		macp = (u16 *) &nettel_macdefault[0];
+
+	mcf_write16(1, NETTEL_SMC0_ADDR + SMC91xx_BANKSELECT);
+	mcf_write16(macp[0], ioaddr + SMC91xx_BASEMAC);
+	mcf_write16(macp[1], ioaddr + SMC91xx_BASEMAC + 2);
+	mcf_write16(macp[2], ioaddr + SMC91xx_BASEMAC + 4);
+}
+
+/***************************************************************************/
+
+/*
+ * Re-map the address space of at least one of the SMC ethernet
+ * parts. Both parts power up decoding the same address, so we
+ * need to move one of them first, before doing anything else.
+ */
+
+static void __init nettel_smc91x_init(void)
+{
+	mcf_write16(0x00ec, MCFSIM_PADDR);
+	mcf_setppdata(0, 0x0080);
+	mcf_write16(1, NETTEL_SMC0_ADDR + SMC91xx_BANKSELECT);
+	mcf_write16(0x0067, NETTEL_SMC0_ADDR + SMC91xx_BASEADDR);
+	mcf_setppdata(0x0080, 0);
+
+	/* Set correct chip select timing for SMC9196 accesses */
+	mcf_write16(0x1180, MCFSIM_CSCR3);
+
+	/* Set the SMC interrupts to be auto-vectored */
+	mcf_autovector(NETTEL_SMC0_IRQ);
+	mcf_autovector(NETTEL_SMC1_IRQ);
+
+	/* Set MAC addresses from flash for both interfaces */
+	nettel_smc91x_setmac(NETTEL_SMC0_ADDR, 0xf0006000);
+	nettel_smc91x_setmac(NETTEL_SMC1_ADDR, 0xf0006006);
+}
+
+/***************************************************************************/
+
+static int __init init_nettel(void)
+{
+	nettel_smc91x_init();
+	platform_add_devices(nettel_devices, ARRAY_SIZE(nettel_devices));
+	return 0;
+}
+
+arch_initcall(init_nettel);
+
+/***************************************************************************/