Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
From:   Ard Biesheuvel <ardb@kernel.org>
To:     linux-crypto@vger.kernel.org
Cc:     herbert@gondor.apana.org.au, keescook@chromium.org,
        Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH 1/8] crypto: add flag for algos that need DMA aligned context buffers
Date:   Wed,  6 Apr 2022 16:27:08 +0200
Message-Id: <20220406142715.2270256-2-ardb@kernel.org>
In-Reply-To: <20220406142715.2270256-1-ardb@kernel.org>
References: <20220406142715.2270256-1-ardb@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

On architectures that support non-coherent DMA, we align and round up
all dynamically allocated request and TFM structures to the worst case
DMA alignment, which is 128 bytes on arm64, even though most systems
only have 64 byte cachelines, are cache coherent for DMA, don't use
use accelerators for crypto, or the driver for the accelerator does not
DMA into the request context buffer to begin with.

We can relax this requirement, by only performing this rounding for
algorithms that are backed by an implementation that actually requires
it. So introduce CRYPTO_ALG_NEED_DMA_ALIGNMENT for this purpose, which
will be wired up in subsequent patches.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 include/linux/crypto.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/crypto.h b/include/linux/crypto.h
index 2324ab6f1846..f2e95fb6cedb 100644
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -100,6 +100,13 @@
  */
 #define CRYPTO_NOLOAD			0x00008000
 
+/*
+ * Whether context buffers require DMA alignment. This is the case for
+ * drivers that perform non-coherent inbound DMA on the context buffer
+ * directly, but should not be needed otherwise.
+ */
+#define CRYPTO_ALG_NEED_DMA_ALIGNMENT	0x00010000
+
 /*
  * The algorithm may allocate memory during request processing, i.e. during
  * encryption, decryption, or hashing.  Users can request an algorithm with this
-- 
2.30.2