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[2620:137:e000::1:20]) by mx.google.com with ESMTP id nc38-20020a1709071c2600b0078e06df0d29si1853250ejc.705.2022.10.12.23.01.37; Wed, 12 Oct 2022 23:02:12 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=RrmEQeGM; spf=pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-crypto-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229516AbiJMF5I (ORCPT + 99 others); Thu, 13 Oct 2022 01:57:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229490AbiJMF5I (ORCPT ); Thu, 13 Oct 2022 01:57:08 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92662127BFC; Wed, 12 Oct 2022 22:57:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 32E4A616FF; Thu, 13 Oct 2022 05:57:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3278EC433C1; Thu, 13 Oct 2022 05:57:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665640626; bh=I/882b5jXItKMfRHTuet95Qg1YMdUHzLfSQFTAbLnZk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RrmEQeGMLGZxFzxAoV3/b27ViZsZ8sPvyFH/rb2Q+/aYAfc/s0zTvJrBv+xrQQRV4 0qG69iZJMsEcMZnpgsrJaoKT9z+O2t/01SsBIniei54pZSa25FiTifJWxvrb9JjoNp L2sQCKRWpyRXOClD7dkdHCgDqIYJhYMsLYvgMBOfzTn/iQ/pL2sOVhSMBdVMl38uqC 6XF3lV82UZWkDg/sA/t8RD0EVIMho9D3k/cWZYSdBLdZlQZEibhhr7LmOu09r6rEAK QzbV6SVHHq4ZM+fRhCMeuGpnJIRaZYihVMDqRycfku3X2UiWqOPldMP0bCbKaudRoB bVtOecleheOag== Date: Wed, 12 Oct 2022 22:57:04 -0700 From: Eric Biggers To: Robert Elliott Cc: herbert@gondor.apana.org.au, davem@davemloft.net, tim.c.chen@linux.intel.com, ap420073@gmail.com, ardb@kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 04/19] crypto: x86/sha - limit FPU preemption Message-ID: References: <20221006223151.22159-1-elliott@hpe.com> <20221012215931.3896-1-elliott@hpe.com> <20221012215931.3896-5-elliott@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221012215931.3896-5-elliott@hpe.com> X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Wed, Oct 12, 2022 at 04:59:16PM -0500, Robert Elliott wrote: > diff --git a/arch/x86/crypto/sha1_ssse3_glue.c b/arch/x86/crypto/sha1_ssse3_glue.c > index 44340a1139e0..a9f5779b41ca 100644 > --- a/arch/x86/crypto/sha1_ssse3_glue.c > +++ b/arch/x86/crypto/sha1_ssse3_glue.c > @@ -26,6 +26,8 @@ > #include > #include > > +#define FPU_BYTES 4096U /* avoid kernel_fpu_begin/end scheduler/rcu stalls */ > + > static int sha1_update(struct shash_desc *desc, const u8 *data, > unsigned int len, sha1_block_fn *sha1_xform) > { > @@ -41,9 +43,18 @@ static int sha1_update(struct shash_desc *desc, const u8 *data, > */ > BUILD_BUG_ON(offsetof(struct sha1_state, state) != 0); > > - kernel_fpu_begin(); > - sha1_base_do_update(desc, data, len, sha1_xform); > - kernel_fpu_end(); > + do { > + unsigned int chunk = min(len, FPU_BYTES); > + > + if (chunk) { > + kernel_fpu_begin(); > + sha1_base_do_update(desc, data, chunk, sha1_xform); > + kernel_fpu_end(); > + } > + > + len -= chunk; > + data += chunk; > + } while (len); 'len' can't be 0 at the beginning of this loop, so the 'if (chunk)' check isn't needed. And it wouldn't make sense even if 'len' could be 0, since a while loop could just be used in that case. - Eric