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, 56 insertions, 0 deletions

diff --git a/include/crypto/internal/poly1305.h b/include/crypto/internal/poly1305.h
new file mode 100644
index 000000000..a72fff409
--- /dev/null
+++ b/include/crypto/internal/poly1305.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common values for the Poly1305 algorithm
+ */
+
+#ifndef _CRYPTO_INTERNAL_POLY1305_H
+#define _CRYPTO_INTERNAL_POLY1305_H
+
+#include <crypto/poly1305.h>
+#include <linux/types.h>
+
+/*
+ * Poly1305 core functions.  These only accept whole blocks; the caller must
+ * handle any needed block buffering and padding.  'hibit' must be 1 for any
+ * full blocks, or 0 for the final block if it had to be padded.  If 'nonce' is
+ * non-NULL, then it's added at the end to compute the Poly1305 MAC.  Otherwise,
+ * only the ε-almost-∆-universal hash function (not the full MAC) is computed.
+ */
+
+void poly1305_core_setkey(struct poly1305_core_key *key,
+			  const u8 raw_key[POLY1305_BLOCK_SIZE]);
+static inline void poly1305_core_init(struct poly1305_state *state)
+{
+	*state = (struct poly1305_state){};
+}
+
+void poly1305_core_blocks(struct poly1305_state *state,
+			  const struct poly1305_core_key *key, const void *src,
+			  unsigned int nblocks, u32 hibit);
+void poly1305_core_emit(const struct poly1305_state *state, const u32 nonce[4],
+			void *dst);
+
+static inline void
+poly1305_block_init_generic(struct poly1305_block_state *desc,
+			    const u8 raw_key[POLY1305_BLOCK_SIZE])
+{
+	poly1305_core_init(&desc->h);
+	poly1305_core_setkey(&desc->core_r, raw_key);
+}
+
+static inline void poly1305_blocks_generic(struct poly1305_block_state *state,
+					   const u8 *src, unsigned int len,
+					   u32 padbit)
+{
+	poly1305_core_blocks(&state->h, &state->core_r, src,
+			     len / POLY1305_BLOCK_SIZE, padbit);
+}
+
+static inline void poly1305_emit_generic(const struct poly1305_state *state,
+					 u8 digest[POLY1305_DIGEST_SIZE],
+					 const u32 nonce[4])
+{
+	poly1305_core_emit(state, nonce, digest);
+}
+
+#endif