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Sun, 3 Mar 2024 16:29:20 +0000 (GMT) Message-ID: <06a094f0-658e-4fb8-9177-3624b8aa760b@linux.ibm.com> Date: Sun, 3 Mar 2024 11:29:20 -0500 Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 04/12] crypto: ecc - Implement vli_mmod_fast_521 for NIST p521 Content-Language: en-US To: Lukas Wunner Cc: keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au, davem@davemloft.net, linux-kernel@vger.kernel.org, saulo.alessandre@tse.jus.br References: <20240301022007.344948-1-stefanb@linux.ibm.com> <20240301022007.344948-5-stefanb@linux.ibm.com> <20240303110511.GA394@wunner.de> From: Stefan Berger In-Reply-To: <20240303110511.GA394@wunner.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: OI6_Nf9C9sDZnPu6tuyLRIHCL7jge32j X-Proofpoint-GUID: OI6_Nf9C9sDZnPu6tuyLRIHCL7jge32j X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-03-03_06,2024-03-01_03,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 spamscore=0 priorityscore=1501 mlxlogscore=984 mlxscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 clxscore=1015 suspectscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2403030138 On 3/3/24 06:05, Lukas Wunner wrote: > On Thu, Feb 29, 2024 at 09:19:59PM -0500, Stefan Berger wrote: >> +static void vli_mmod_fast_521(u64 *result, const u64 *product, >> + const u64 *curve_prime, u64 *tmp) >> +{ >> + const unsigned int ndigits = 9; >> + size_t i; >> + >> + for (i = 0; i < ndigits; i++) >> + tmp[i] = product[i]; >> + tmp[8] &= 0x1ff; > > Hm, the other vli_mmod_fast_*() functions manually unroll those loops. > Wondering if that would make sense here as well? It's also possible Why would we do this? One could also argue why not use vli_set() instead of the loop... > to tell gcc to unroll a loop with a per-function... > > __attribute__((optimize("unroll-loops"))) > > ...but I'm not sure about clang portability. > > >> @@ -941,6 +966,12 @@ static bool vli_mmod_fast(u64 *result, u64 *product, >> + case 9: >> + if (!strcmp(curve->name, "nist_521")) { >> + vli_mmod_fast_521(result, product, curve_prime, tmp); >> + break; >> + } >> + fallthrough; > > If you reorder patch 4 and 5, you could check for curve->nbits == 521 here, > which might be cheaper than the string comparison. Sure. I thought it's a nist spec for this particular curve, so compare against 'nist' in the string. Though comparing against nbits also works, of course. > > >> -#define ECC_MAX_DIGITS (512 / 64) /* due to ecrdsa */ >> +#define ECC_MAX_DIGITS (576 / 64) /* due to NIST P521 */ > > Maybe DIV_ROUND_UP(521, 64) for clarity? Ok, will adjust. Regards, Stefan > > Thanks, > > Lukas >