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, 170 insertions, 0 deletions

diff --git a/lib/crypto/blake2b.c b/lib/crypto/blake2b.c
new file mode 100644
index 000000000..581b7f848
--- /dev/null
+++ b/lib/crypto/blake2b.c
@@ -0,0 +1,170 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ * Copyright 2025 Google LLC
+ *
+ * This is an implementation of the BLAKE2b hash and PRF functions.
+ *
+ * Information: https://blake2.net/
+ */
+
+#include <crypto/blake2b.h>
+#include <linux/bug.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/unroll.h>
+#include <linux/types.h>
+
+static const u8 blake2b_sigma[12][16] = {
+	{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+	{ 14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3 },
+	{ 11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4 },
+	{ 7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8 },
+	{ 9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13 },
+	{ 2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9 },
+	{ 12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11 },
+	{ 13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10 },
+	{ 6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5 },
+	{ 10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0 },
+	{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+	{ 14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3 }
+};
+
+static inline void blake2b_increment_counter(struct blake2b_ctx *ctx, u32 inc)
+{
+	ctx->t[0] += inc;
+	ctx->t[1] += (ctx->t[0] < inc);
+}
+
+static void __maybe_unused
+blake2b_compress_generic(struct blake2b_ctx *ctx,
+			 const u8 *data, size_t nblocks, u32 inc)
+{
+	u64 m[16];
+	u64 v[16];
+	int i;
+
+	WARN_ON(IS_ENABLED(DEBUG) &&
+		(nblocks > 1 && inc != BLAKE2B_BLOCK_SIZE));
+
+	while (nblocks > 0) {
+		blake2b_increment_counter(ctx, inc);
+		memcpy(m, data, BLAKE2B_BLOCK_SIZE);
+		le64_to_cpu_array(m, ARRAY_SIZE(m));
+		memcpy(v, ctx->h, 64);
+		v[ 8] = BLAKE2B_IV0;
+		v[ 9] = BLAKE2B_IV1;
+		v[10] = BLAKE2B_IV2;
+		v[11] = BLAKE2B_IV3;
+		v[12] = BLAKE2B_IV4 ^ ctx->t[0];
+		v[13] = BLAKE2B_IV5 ^ ctx->t[1];
+		v[14] = BLAKE2B_IV6 ^ ctx->f[0];
+		v[15] = BLAKE2B_IV7 ^ ctx->f[1];
+
+#define G(r, i, a, b, c, d) do { \
+	a += b + m[blake2b_sigma[r][2 * i + 0]]; \
+	d = ror64(d ^ a, 32); \
+	c += d; \
+	b = ror64(b ^ c, 24); \
+	a += b + m[blake2b_sigma[r][2 * i + 1]]; \
+	d = ror64(d ^ a, 16); \
+	c += d; \
+	b = ror64(b ^ c, 63); \
+} while (0)
+
+#ifdef CONFIG_64BIT
+		/*
+		 * Unroll the rounds loop to enable constant-folding of the
+		 * blake2b_sigma values.  Seems worthwhile on 64-bit kernels.
+		 * Not worthwhile on 32-bit kernels because the code size is
+		 * already so large there due to BLAKE2b using 64-bit words.
+		 */
+		unrolled_full
+#endif
+		for (int r = 0; r < 12; r++) {
+			G(r, 0, v[0], v[4], v[8], v[12]);
+			G(r, 1, v[1], v[5], v[9], v[13]);
+			G(r, 2, v[2], v[6], v[10], v[14]);
+			G(r, 3, v[3], v[7], v[11], v[15]);
+			G(r, 4, v[0], v[5], v[10], v[15]);
+			G(r, 5, v[1], v[6], v[11], v[12]);
+			G(r, 6, v[2], v[7], v[8], v[13]);
+			G(r, 7, v[3], v[4], v[9], v[14]);
+		}
+#undef G
+
+		for (i = 0; i < 8; ++i)
+			ctx->h[i] ^= v[i] ^ v[i + 8];
+
+		data += BLAKE2B_BLOCK_SIZE;
+		--nblocks;
+	}
+}
+
+#ifdef CONFIG_CRYPTO_LIB_BLAKE2B_ARCH
+#include "blake2b.h" /* $(SRCARCH)/blake2b.h */
+#else
+#define blake2b_compress blake2b_compress_generic
+#endif
+
+static inline void blake2b_set_lastblock(struct blake2b_ctx *ctx)
+{
+	ctx->f[0] = -1;
+}
+
+void blake2b_update(struct blake2b_ctx *ctx, const u8 *in, size_t inlen)
+{
+	const size_t fill = BLAKE2B_BLOCK_SIZE - ctx->buflen;
+
+	if (unlikely(!inlen))
+		return;
+	if (inlen > fill) {
+		memcpy(ctx->buf + ctx->buflen, in, fill);
+		blake2b_compress(ctx, ctx->buf, 1, BLAKE2B_BLOCK_SIZE);
+		ctx->buflen = 0;
+		in += fill;
+		inlen -= fill;
+	}
+	if (inlen > BLAKE2B_BLOCK_SIZE) {
+		const size_t nblocks = DIV_ROUND_UP(inlen, BLAKE2B_BLOCK_SIZE);
+
+		blake2b_compress(ctx, in, nblocks - 1, BLAKE2B_BLOCK_SIZE);
+		in += BLAKE2B_BLOCK_SIZE * (nblocks - 1);
+		inlen -= BLAKE2B_BLOCK_SIZE * (nblocks - 1);
+	}
+	memcpy(ctx->buf + ctx->buflen, in, inlen);
+	ctx->buflen += inlen;
+}
+EXPORT_SYMBOL(blake2b_update);
+
+void blake2b_final(struct blake2b_ctx *ctx, u8 *out)
+{
+	WARN_ON(IS_ENABLED(DEBUG) && !out);
+	blake2b_set_lastblock(ctx);
+	memset(ctx->buf + ctx->buflen, 0,
+	       BLAKE2B_BLOCK_SIZE - ctx->buflen); /* Padding */
+	blake2b_compress(ctx, ctx->buf, 1, ctx->buflen);
+	cpu_to_le64_array(ctx->h, ARRAY_SIZE(ctx->h));
+	memcpy(out, ctx->h, ctx->outlen);
+	memzero_explicit(ctx, sizeof(*ctx));
+}
+EXPORT_SYMBOL(blake2b_final);
+
+#ifdef blake2b_mod_init_arch
+static int __init blake2b_mod_init(void)
+{
+	blake2b_mod_init_arch();
+	return 0;
+}
+subsys_initcall(blake2b_mod_init);
+
+static void __exit blake2b_mod_exit(void)
+{
+}
+module_exit(blake2b_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("BLAKE2b hash function");
+MODULE_LICENSE("GPL");