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, 196 insertions, 0 deletions

diff --git a/include/net/snmp.h b/include/net/snmp.h
new file mode 100644
index 000000000..584e70742
--- /dev/null
+++ b/include/net/snmp.h
@@ -0,0 +1,196 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *
+ *		SNMP MIB entries for the IP subsystem.
+ *		
+ *		Alan Cox <gw4pts@gw4pts.ampr.org>
+ *
+ *		We don't chose to implement SNMP in the kernel (this would
+ *		be silly as SNMP is a pain in the backside in places). We do
+ *		however need to collect the MIB statistics and export them
+ *		out of /proc (eventually)
+ */
+ 
+#ifndef _SNMP_H
+#define _SNMP_H
+
+#include <linux/cache.h>
+#include <linux/snmp.h>
+#include <linux/smp.h>
+
+/*
+ * Mibs are stored in array of unsigned long.
+ */
+/*
+ * struct snmp_mib{}
+ *  - list of entries for particular API (such as /proc/net/snmp)
+ *  - name of entries.
+ */
+struct snmp_mib {
+	const char *name;
+	int entry;
+};
+
+#define SNMP_MIB_ITEM(_name,_entry)	{	\
+	.name = _name,				\
+	.entry = _entry,			\
+}
+
+/*
+ * We use unsigned longs for most mibs but u64 for ipstats.
+ */
+#include <linux/u64_stats_sync.h>
+
+/* IPstats */
+#define IPSTATS_MIB_MAX	__IPSTATS_MIB_MAX
+struct ipstats_mib {
+	/* mibs[] must be first field of struct ipstats_mib */
+	u64		mibs[IPSTATS_MIB_MAX];
+	struct u64_stats_sync syncp;
+};
+
+/* ICMP */
+#define ICMP_MIB_MAX	__ICMP_MIB_MAX
+struct icmp_mib {
+	unsigned long	mibs[ICMP_MIB_MAX];
+};
+
+#define ICMPMSG_MIB_MAX	__ICMPMSG_MIB_MAX
+struct icmpmsg_mib {
+	atomic_long_t	mibs[ICMPMSG_MIB_MAX];
+};
+
+/* ICMP6 (IPv6-ICMP) */
+#define ICMP6_MIB_MAX	__ICMP6_MIB_MAX
+/* per network ns counters */
+struct icmpv6_mib {
+	unsigned long	mibs[ICMP6_MIB_MAX];
+};
+/* per device counters, (shared on all cpus) */
+struct icmpv6_mib_device {
+	atomic_long_t	mibs[ICMP6_MIB_MAX];
+};
+
+#define ICMP6MSG_MIB_MAX  __ICMP6MSG_MIB_MAX
+/* per network ns counters */
+struct icmpv6msg_mib {
+	atomic_long_t	mibs[ICMP6MSG_MIB_MAX];
+};
+/* per device counters, (shared on all cpus) */
+struct icmpv6msg_mib_device {
+	atomic_long_t	mibs[ICMP6MSG_MIB_MAX];
+};
+
+
+/* TCP */
+#define TCP_MIB_MAX	__TCP_MIB_MAX
+struct tcp_mib {
+	unsigned long	mibs[TCP_MIB_MAX];
+};
+
+/* UDP */
+#define UDP_MIB_MAX	__UDP_MIB_MAX
+struct udp_mib {
+	unsigned long	mibs[UDP_MIB_MAX];
+};
+
+/* Linux */
+#define LINUX_MIB_MAX	__LINUX_MIB_MAX
+struct linux_mib {
+	unsigned long	mibs[LINUX_MIB_MAX];
+};
+
+/* Linux Xfrm */
+#define LINUX_MIB_XFRMMAX	__LINUX_MIB_XFRMMAX
+struct linux_xfrm_mib {
+	unsigned long	mibs[LINUX_MIB_XFRMMAX];
+};
+
+/* Linux TLS */
+#define LINUX_MIB_TLSMAX	__LINUX_MIB_TLSMAX
+struct linux_tls_mib {
+	unsigned long	mibs[LINUX_MIB_TLSMAX];
+};
+
+#define DEFINE_SNMP_STAT(type, name)	\
+	__typeof__(type) __percpu *name
+#define DEFINE_SNMP_STAT_ATOMIC(type, name)	\
+	__typeof__(type) *name
+#define DECLARE_SNMP_STAT(type, name)	\
+	extern __typeof__(type) __percpu *name
+
+#define __SNMP_INC_STATS(mib, field)	\
+			__this_cpu_inc(mib->mibs[field])
+
+#define SNMP_INC_STATS_ATOMIC_LONG(mib, field)	\
+			atomic_long_inc(&mib->mibs[field])
+
+#define SNMP_INC_STATS(mib, field)	\
+			this_cpu_inc(mib->mibs[field])
+
+#define SNMP_DEC_STATS(mib, field)	\
+			this_cpu_dec(mib->mibs[field])
+
+#define __SNMP_ADD_STATS(mib, field, addend)	\
+			__this_cpu_add(mib->mibs[field], addend)
+
+#define SNMP_ADD_STATS(mib, field, addend)	\
+			this_cpu_add(mib->mibs[field], addend)
+#define SNMP_UPD_PO_STATS(mib, basefield, addend)	\
+	do { \
+		__typeof__((mib->mibs) + 0) ptr = mib->mibs;	\
+		this_cpu_inc(ptr[basefield##PKTS]);		\
+		this_cpu_add(ptr[basefield##OCTETS], addend);	\
+	} while (0)
+#define __SNMP_UPD_PO_STATS(mib, basefield, addend)	\
+	do { \
+		__typeof__((mib->mibs) + 0) ptr = mib->mibs;	\
+		__this_cpu_inc(ptr[basefield##PKTS]);		\
+		__this_cpu_add(ptr[basefield##OCTETS], addend);	\
+	} while (0)
+
+
+#if BITS_PER_LONG==32
+
+#define __SNMP_ADD_STATS64(mib, field, addend) 				\
+	do {								\
+		TYPEOF_UNQUAL(*mib) *ptr = raw_cpu_ptr(mib);		\
+		u64_stats_update_begin(&ptr->syncp);			\
+		ptr->mibs[field] += addend;				\
+		u64_stats_update_end(&ptr->syncp);			\
+	} while (0)
+
+#define SNMP_ADD_STATS64(mib, field, addend) 				\
+	do {								\
+		local_bh_disable();					\
+		__SNMP_ADD_STATS64(mib, field, addend);			\
+		local_bh_enable();				\
+	} while (0)
+
+#define __SNMP_INC_STATS64(mib, field) SNMP_ADD_STATS64(mib, field, 1)
+#define SNMP_INC_STATS64(mib, field) SNMP_ADD_STATS64(mib, field, 1)
+#define __SNMP_UPD_PO_STATS64(mib, basefield, addend)			\
+	do {								\
+		TYPEOF_UNQUAL(*mib) *ptr = raw_cpu_ptr(mib);		\
+		u64_stats_update_begin(&ptr->syncp);			\
+		ptr->mibs[basefield##PKTS]++;				\
+		ptr->mibs[basefield##OCTETS] += addend;			\
+		u64_stats_update_end(&ptr->syncp);			\
+	} while (0)
+#define SNMP_UPD_PO_STATS64(mib, basefield, addend)			\
+	do {								\
+		local_bh_disable();					\
+		__SNMP_UPD_PO_STATS64(mib, basefield, addend);		\
+		local_bh_enable();				\
+	} while (0)
+#else
+#define __SNMP_INC_STATS64(mib, field)		__SNMP_INC_STATS(mib, field)
+#define SNMP_INC_STATS64(mib, field)		SNMP_INC_STATS(mib, field)
+#define SNMP_DEC_STATS64(mib, field)		SNMP_DEC_STATS(mib, field)
+#define __SNMP_ADD_STATS64(mib, field, addend)	__SNMP_ADD_STATS(mib, field, addend)
+#define SNMP_ADD_STATS64(mib, field, addend)	SNMP_ADD_STATS(mib, field, addend)
+#define SNMP_UPD_PO_STATS64(mib, basefield, addend) SNMP_UPD_PO_STATS(mib, basefield, addend)
+#define __SNMP_UPD_PO_STATS64(mib, basefield, addend) __SNMP_UPD_PO_STATS(mib, basefield, addend)
+#endif
+
+#endif