linux-kernel - Re: [PATCH 06/12] RISC-V: crypto: add accelerated AES-CBC/CTR/ECB/XTS implementations

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Date:   Tue, 7 Nov 2023 16:53:13 +0800
From:   Jerry Shih <jerry.shih@...ive.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>, palmer@...belt.com,
        Albert Ou <aou@...s.berkeley.edu>, herbert@...dor.apana.org.au,
        davem@...emloft.net, andy.chiu@...ive.com, greentime.hu@...ive.com,
        conor.dooley@...rochip.com, guoren@...nel.org, bjorn@...osinc.com,
        heiko@...ech.de, ardb@...nel.org, phoebe.chen@...ive.com,
        hongrong.hsu@...ive.com, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH 06/12] RISC-V: crypto: add accelerated AES-CBC/CTR/ECB/XTS
 implementations

On Nov 2, 2023, at 13:16, Eric Biggers <ebiggers@...nel.org> wrote:
> On Thu, Oct 26, 2023 at 02:36:38AM +0800, Jerry Shih wrote:
>> +static int ecb_encrypt(struct skcipher_request *req)
>> +{
>> +	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
>> +	const struct riscv64_aes_ctx *ctx = crypto_skcipher_ctx(tfm);
>> +	struct skcipher_walk walk;
>> +	unsigned int nbytes;
>> +	int err;
>> +
>> +	/* If we have error here, the `nbytes` will be zero. */
>> +	err = skcipher_walk_virt(&walk, req, false);
>> +	while ((nbytes = walk.nbytes)) {
>> +		kernel_vector_begin();
>> +		rv64i_zvkned_ecb_encrypt(walk.src.virt.addr, walk.dst.virt.addr,
>> +					 nbytes & AES_BLOCK_VALID_SIZE_MASK,
>> +					 &ctx->key);
>> +		kernel_vector_end();
>> +		err = skcipher_walk_done(
>> +			&walk, nbytes & AES_BLOCK_REMAINING_SIZE_MASK);
>> +	}
>> +
>> +	return err;
>> +}
> 
> There's no fallback for !crypto_simd_usable() here.  I really like it this way.
> However, for it to work (for skciphers and aeads), RISC-V needs to allow the
> vector registers to be used in softirq context.  Is that already the case?

The kernel-mode-vector could be enabled in softirq, but we don't have nesting
vector contexts. Will we have the case that kernel needs to jump to softirq for
encryptions during the regular crypto function? If yes, we need to have fallbacks
for all algorithms.

-Jerry