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Subject: Re: [PATCH v2 04/13] RISC-V: crypto: add Zvkned accelerated AES
 implementation
From:   Jerry Shih <jerry.shih@sifive.com>
In-Reply-To: <20231128035630.GG1463@sol.localdomain>
Date:   Tue, 28 Nov 2023 12:22:26 +0800
Cc:     Paul Walmsley <paul.walmsley@sifive.com>, palmer@dabbelt.com,
        Albert Ou <aou@eecs.berkeley.edu>, herbert@gondor.apana.org.au,
        davem@davemloft.net, conor.dooley@microchip.com, ardb@kernel.org,
        heiko@sntech.de, phoebe.chen@sifive.com, hongrong.hsu@sifive.com,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-crypto@vger.kernel.org
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References: <20231127070703.1697-1-jerry.shih@sifive.com>
 <20231127070703.1697-5-jerry.shih@sifive.com>
 <20231128035630.GG1463@sol.localdomain>
To:     Eric Biggers <ebiggers@kernel.org>
Precedence: bulk

On Nov 28, 2023, at 11:56, Eric Biggers <ebiggers@kernel.org> wrote:
> On Mon, Nov 27, 2023 at 03:06:54PM +0800, Jerry Shih wrote:
>> +int riscv64_aes_setkey(struct crypto_aes_ctx *ctx, const u8 *key,
>> +		       unsigned int keylen)
>> +{
>> +	int ret;
>> +
>> +	ret =3D aes_check_keylen(keylen);
>> +	if (ret < 0)
>> +		return -EINVAL;
>> +
>> +	/*
>> +	 * The RISC-V AES vector crypto key expanding doesn't support =
AES-192.
>> +	 * Use the generic software key expanding for that case.
>> +	 */
>> +	if ((keylen =3D=3D 16 || keylen =3D=3D 32) && =
crypto_simd_usable()) {
>> +		/*
>> +		 * All zvkned-based functions use encryption expanding =
keys for both
>> +		 * encryption and decryption.
>> +		 */
>> +		kernel_vector_begin();
>> +		rv64i_zvkned_set_encrypt_key(key, keylen, ctx);
>> +		kernel_vector_end();
>> +	} else {
>> +		ret =3D aes_expandkey(ctx, key, keylen);
>> +	}
>=20
> rv64i_zvkned_set_encrypt_key() does not initialize =
crypto_aes_ctx::key_dec.
> So, decryption results will be incorrect if !crypto_simd_usable() =
later.

Will we have the situation that `crypto_simd_usable()` condition is not =
consistent
during the aes_setkey(), aes_enc/dec()? If yes, all accelerated(or HW =
specific)
crypto algorithms should do the same implementations as the sw fallback =
path
since the `crypto_simd_usable()` will change back and forth.

>> +static int aes_setkey(struct crypto_tfm *tfm, const u8 *key,
>> +		      unsigned int keylen)
>=20
> It's best to avoid generic-sounding function names like this that =
could collide
> with functions in crypto/ or lib/crypto/.  A better name for this =
function, for
> example, would be aes_setkey_zvkned().

Thx, I will fix that.

>> diff --git a/arch/riscv/crypto/aes-riscv64-zvkned.pl =
b/arch/riscv/crypto/aes-riscv64-zvkned.pl
>> new file mode 100644
>> index 000000000000..303e82d9f6f0
>> --- /dev/null
>> +++ b/arch/riscv/crypto/aes-riscv64-zvkned.pl
> [...]
>> +L_enc_128:
> [...]
>> +L_enc_192:
> [...]
>> +L_enc_256:
>=20
> There's some severe source code duplication going on in the AES =
assembly, with
> the three AES variants having separate source code.  You can just =
leave this
> as-is since this is what was merged into OpenSSL and we are borrowing =
that for
> now, but I do expect that we'll want to clean this up later.

Do we prefer the code with the branches instead of the specified =
implementation?
We could make AES-128/192/256 together like:

    @{[vaesz_vs $V24, $V1]}
    @{[vaesem_vs $V24, $V2]}
    @{[vaesem_vs $V24, $V3]}
    @{[vaesem_vs $V24, $V4]}
    @{[vaesem_vs $V24, $V5]}
    @{[vaesem_vs $V24, $V6]}
    @{[vaesem_vs $V24, $V7]}
    @{[vaesem_vs $V24, $V8]}
    @{[vaesem_vs $V24, $V9]}
    @{[vaesem_vs $V24, $V10]}
    beq $ROUND, $ROUND_11, 1f
    @{[vaesem_vs $V24, $V11]}
    @{[vaesem_vs $V24, $V12]}
    beq $ROUND, $ROUND_13, 1f
    @{[vaesem_vs $V24, $V13]}
    @{[vaesem_vs $V24, $V14]}
1:
    @{[vaesef_vs $V24, $V15]}

But we will have the additional costs for the branches.

> - Eric