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, 159 insertions, 0 deletions

diff --git a/drivers/media/common/ttpci-eeprom.c b/drivers/media/common/ttpci-eeprom.c
new file mode 100644
index 000000000..ef8746684
--- /dev/null
+++ b/drivers/media/common/ttpci-eeprom.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+    Retrieve encoded MAC address from 24C16 serial 2-wire EEPROM,
+    decode it and store it in the associated adapter struct for
+    use by dvb_net.c
+
+    This card appear to have the 24C16 write protect held to ground,
+    thus permitting normal read/write operation. Theoretically it
+    would be possible to write routines to burn a different (encoded)
+    MAC address into the EEPROM.
+
+    Robert Schlabbach	GMX
+    Michael Glaum	KVH Industries
+    Holger Waechtler	Convergence
+
+    Copyright (C) 2002-2003 Ralph Metzler <rjkm@metzlerbros.de>
+			    Metzler Brothers Systementwicklung GbR
+
+
+*/
+
+#include <asm/errno.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/i2c.h>
+#include <linux/etherdevice.h>
+
+#include "ttpci-eeprom.h"
+
+#if 1
+#define dprintk(x...) do { printk(x); } while (0)
+#else
+#define dprintk(x...) do { } while (0)
+#endif
+
+
+static int check_mac_tt(u8 *buf)
+{
+	int i;
+	u16 tmp = 0xffff;
+
+	for (i = 0; i < 8; i++) {
+		tmp  = (tmp << 8) | ((tmp >> 8) ^ buf[i]);
+		tmp ^= (tmp >> 4) & 0x0f;
+		tmp ^= (tmp << 12) ^ ((tmp & 0xff) << 5);
+	}
+	tmp ^= 0xffff;
+	return (((tmp >> 8) ^ buf[8]) | ((tmp & 0xff) ^ buf[9]));
+}
+
+static int getmac_tt(u8 * decodedMAC, u8 * encodedMAC)
+{
+	u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
+		       0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
+		       0x1d, 0x36, 0x64, 0x78};
+	u8 data[20];
+	int i;
+
+	/* In case there is a sig check failure have the orig contents available */
+	memcpy(data, encodedMAC, 20);
+
+	for (i = 0; i < 20; i++)
+		data[i] ^= xor[i];
+	for (i = 0; i < 10; i++)
+		data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
+			>> ((data[2 * i + 1] >> 6) & 3);
+
+	if (check_mac_tt(data))
+		return -ENODEV;
+
+	decodedMAC[0] = data[2]; decodedMAC[1] = data[1]; decodedMAC[2] = data[0];
+	decodedMAC[3] = data[6]; decodedMAC[4] = data[5]; decodedMAC[5] = data[4];
+	return 0;
+}
+
+int ttpci_eeprom_decode_mac(u8 *decodedMAC, u8 *encodedMAC)
+{
+	u8 xor[20] = { 0x72, 0x23, 0x68, 0x19, 0x5c, 0xa8, 0x71, 0x2c,
+		       0x54, 0xd3, 0x7b, 0xf1, 0x9E, 0x23, 0x16, 0xf6,
+		       0x1d, 0x36, 0x64, 0x78};
+	u8 data[20];
+	int i;
+
+	memcpy(data, encodedMAC, 20);
+
+	for (i = 0; i < 20; i++)
+		data[i] ^= xor[i];
+	for (i = 0; i < 10; i++)
+		data[i] = ((data[2 * i + 1] << 8) | data[2 * i])
+			>> ((data[2 * i + 1] >> 6) & 3);
+
+	if (check_mac_tt(data))
+		return -ENODEV;
+
+	decodedMAC[0] = data[2];
+	decodedMAC[1] = data[1];
+	decodedMAC[2] = data[0];
+	decodedMAC[3] = data[6];
+	decodedMAC[4] = data[5];
+	decodedMAC[5] = data[4];
+	return 0;
+}
+EXPORT_SYMBOL(ttpci_eeprom_decode_mac);
+
+static int ttpci_eeprom_read_encodedMAC(struct i2c_adapter *adapter, u8 * encodedMAC)
+{
+	int ret;
+	u8 b0[] = { 0xcc };
+
+	struct i2c_msg msg[] = {
+		{ .addr = 0x50, .flags = 0, .buf = b0, .len = 1 },
+		{ .addr = 0x50, .flags = I2C_M_RD, .buf = encodedMAC, .len = 20 }
+	};
+
+	/* dprintk("%s\n", __func__); */
+
+	ret = i2c_transfer(adapter, msg, 2);
+
+	if (ret != 2)		/* Assume EEPROM isn't there */
+		return (-ENODEV);
+
+	return 0;
+}
+
+
+int ttpci_eeprom_parse_mac(struct i2c_adapter *adapter, u8 *proposed_mac)
+{
+	int ret;
+	u8 encodedMAC[20];
+	u8 decodedMAC[6];
+
+	ret = ttpci_eeprom_read_encodedMAC(adapter, encodedMAC);
+
+	if (ret != 0) {		/* Will only be -ENODEV */
+		dprintk("Couldn't read from EEPROM: not there?\n");
+		eth_zero_addr(proposed_mac);
+		return ret;
+	}
+
+	ret = getmac_tt(decodedMAC, encodedMAC);
+	if( ret != 0 ) {
+		dprintk("adapter failed MAC signature check\n");
+		dprintk("encoded MAC from EEPROM was %*phC",
+			(int)sizeof(encodedMAC), &encodedMAC);
+		eth_zero_addr(proposed_mac);
+		return ret;
+	}
+
+	memcpy(proposed_mac, decodedMAC, 6);
+	dprintk("adapter has MAC addr = %pM\n", decodedMAC);
+	return 0;
+}
+
+EXPORT_SYMBOL(ttpci_eeprom_parse_mac);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Ralph Metzler, Marcus Metzler, others");
+MODULE_DESCRIPTION("Decode dvb_net MAC address from EEPROM of PCI DVB cards made by Siemens, Technotrend, Hauppauge");