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, 103 insertions, 0 deletions

diff --git a/crypto/proc.c b/crypto/proc.c
new file mode 100644
index 000000000..5fb9fe86d
--- /dev/null
+++ b/crypto/proc.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Scatterlist Cryptographic API.
+ *
+ * Procfs information.
+ *
+ * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
+ * Copyright (c) 2005 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <linux/atomic.h>
+#include <linux/init.h>
+#include <linux/crypto.h>
+#include <linux/fips.h>
+#include <linux/module.h>	/* for module_name() */
+#include <linux/rwsem.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+
+static void *c_start(struct seq_file *m, loff_t *pos)
+	__acquires_shared(&crypto_alg_sem)
+{
+	down_read(&crypto_alg_sem);
+	return seq_list_start(&crypto_alg_list, *pos);
+}
+
+static void *c_next(struct seq_file *m, void *p, loff_t *pos)
+	__must_hold_shared(&crypto_alg_sem)
+{
+	return seq_list_next(p, &crypto_alg_list, pos);
+}
+
+static void c_stop(struct seq_file *m, void *p)
+	__releases_shared(&crypto_alg_sem)
+{
+	up_read(&crypto_alg_sem);
+}
+
+static int c_show(struct seq_file *m, void *p)
+{
+	struct crypto_alg *alg = list_entry(p, struct crypto_alg, cra_list);
+
+	seq_printf(m, "name         : %s\n", alg->cra_name);
+	seq_printf(m, "driver       : %s\n", alg->cra_driver_name);
+	seq_printf(m, "module       : %s\n", module_name(alg->cra_module));
+	seq_printf(m, "priority     : %d\n", alg->cra_priority);
+	seq_printf(m, "refcnt       : %u\n", refcount_read(&alg->cra_refcnt));
+	seq_printf(m, "selftest     : %s\n",
+		   (alg->cra_flags & CRYPTO_ALG_TESTED) ?
+		   "passed" : "unknown");
+	seq_printf(m, "internal     : %s\n",
+		   str_yes_no(alg->cra_flags & CRYPTO_ALG_INTERNAL));
+	if (fips_enabled)
+		seq_printf(m, "fips         : %s\n",
+			str_no_yes(alg->cra_flags & CRYPTO_ALG_FIPS_INTERNAL));
+
+	if (alg->cra_flags & CRYPTO_ALG_LARVAL) {
+		seq_printf(m, "type         : larval\n");
+		seq_printf(m, "flags        : 0x%x\n", alg->cra_flags);
+		goto out;
+	}
+
+	if (alg->cra_type && alg->cra_type->show) {
+		alg->cra_type->show(m, alg);
+		goto out;
+	}
+
+	switch (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) {
+	case CRYPTO_ALG_TYPE_CIPHER:
+		seq_printf(m, "type         : cipher\n");
+		seq_printf(m, "blocksize    : %u\n", alg->cra_blocksize);
+		seq_printf(m, "min keysize  : %u\n",
+					alg->cra_cipher.cia_min_keysize);
+		seq_printf(m, "max keysize  : %u\n",
+					alg->cra_cipher.cia_max_keysize);
+		break;
+	default:
+		seq_printf(m, "type         : unknown\n");
+		break;
+	}
+
+out:
+	seq_putc(m, '\n');
+	return 0;
+}
+
+static const struct seq_operations crypto_seq_ops = {
+	.start		= c_start,
+	.next		= c_next,
+	.stop		= c_stop,
+	.show		= c_show
+};
+
+void __init crypto_init_proc(void)
+{
+	proc_create_seq("crypto", 0, NULL, &crypto_seq_ops);
+}
+
+void __exit crypto_exit_proc(void)
+{
+	remove_proc_entry("crypto", NULL);
+}