From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46846C4338F for ; Mon, 26 Jul 2021 19:50:10 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C66BC60BD3 for ; Mon, 26 Jul 2021 19:50:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org C66BC60BD3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:36160 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m86c4-0004aO-Rv for qemu-devel@archiver.kernel.org; Mon, 26 Jul 2021 15:50:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45232) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m86KO-00078C-Gh for qemu-devel@nongnu.org; Mon, 26 Jul 2021 15:31:52 -0400 Received: from mail-ej1-x635.google.com ([2a00:1450:4864:20::635]:46914) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1m86KM-0007X7-Rv for qemu-devel@nongnu.org; Mon, 26 Jul 2021 15:31:52 -0400 Received: by mail-ej1-x635.google.com with SMTP id gs8so4690576ejc.13 for ; Mon, 26 Jul 2021 12:31:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=/a70QBgbIE7hQypRWMRCRGdEit5b4RjdP6E1ZyGbBkg=; b=pCcLMY3GUlaoIAVB7w0e1mQAQNpiQMFoDVSDuv93Gam6++hlTSQuaM+OsAs10q34Le 2goYlsAeK2/Ngg87zTJgWQHeLHqAxXj1Db3nxXnSKTQTjzu8I7Bv1f5/oMiGxLK+fqGk M4hdG/ENvOkB9tLN1I3DH8U/4hOcb9yM3uA5qcYHROkxgLkZ6ysYW73I/wECYyg87GV8 EJSMGmnw99Lvw3A9yEdtv0PzCyxZVj9FzOHApVZsRdoXgxEfrGyYpxkwtEMqL26pE7uH eJYaaCtmMZsXK/EGfPKKdKTlzGhdlLYEc+bcTeLh4FKBY54XkhN17d2s2jmvEiOXa6pc Yk6g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/a70QBgbIE7hQypRWMRCRGdEit5b4RjdP6E1ZyGbBkg=; b=dUvJ01OeCXazoc/a8uNotttgeKSSuveamq24mnPgQOu96ihLfFnNOn3x9KufveDyDZ JqEdVIuUKbirGJ5AovAfA/Ph7ubbd1Edhw5Y4glZOTFoO7UlOU+o6q+Vv6sfq+Bbszga 1mFU2Q8qfi0yd9G1DDFXASTzkVuOiUaVCSOmP2SMiLwJ2qHmGcjfVqrN6uhD85SWV6H4 IQepMbCw0vA41gd7M13bj7KFsQmdGQ3w6GpSN1uz9ucdhP/4iqRjHT9xrSYJ++a5EWkj cjKkOsc2zisbHmnO/T6aoUqyioCqBD+OPjEHXwEyy5oYLpmBJvh12WDuAoq2Sn8lbatr ZohA== X-Gm-Message-State: AOAM533V6BlOYMiuyAeaxwnTmrYfadl0EHwdYjg+cw+fKR6/ME0QfyXS p5ax+XdVMK2naembq3vO8d09ruWDQmV0sylirAiKKw== X-Google-Smtp-Source: ABdhPJzQM2JK9nFv+NhtoJpG7pusKxoBgveHAq8EX1UgdxXtnVlqPSBXzu8bGAVu19x6Mr9861TbnBXKCPELTqpSGDo= X-Received: by 2002:a17:906:a108:: with SMTP id t8mr18453360ejy.407.1627327909205; Mon, 26 Jul 2021 12:31:49 -0700 (PDT) MIME-Version: 1.0 References: <20210723203344.968563-1-richard.henderson@linaro.org> <20210723203344.968563-4-richard.henderson@linaro.org> <20210726145951.g3ywwhcfstmsi7vi@gator> In-Reply-To: From: Peter Maydell Date: Mon, 26 Jul 2021 20:31:07 +0100 Message-ID: Subject: Re: [PATCH v2 3/3] target/arm: Add sve-default-vector-length cpu property To: Richard Henderson Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2a00:1450:4864:20::635; envelope-from=peter.maydell@linaro.org; helo=mail-ej1-x635.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrew Jones , qemu-arm , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 26 Jul 2021 at 19:34, Richard Henderson wrote: > > On 7/26/21 4:59 AM, Andrew Jones wrote: > >> +SVE User-mode Default Vector Length Property > >> +-------------------------------------------- > >> + > >> +For qemu-aarch64, the cpu property `sve-default-vector-length=N` is > >> +defined to mirror the Linux kernel parameter file > >> +`/proc/sys/abi/sve_default_vector_length`. The default length, `N`, > >> +is in units of bytes and must be between 16 and 8192. > > > > Hmm. If a user inputs anything greater than 256, then won't it get > > silently reduced to 256? > > Yes. > > >> +If not specified, the default vector length is 64. > >> + > >> +If the default length is larger than the maximum vector length enabled > >> +with `sve` properties, the actual vector length will be reduced. > > > > Here it's pointed out that the default may be reduced, but it implies that > > that only happens if an sve property is also given. Won't users wonder > > why they're only getting vectors that are 256 bytes large even when they > > ask for more? > > I guess adding that 256 is the maximum length supported by qemu should be sufficient? Could you either provide a fixup diff for me to fold into this patch or else repost a new version? (I don't mind which; if it's just a docs tweak fixup diff is probably simplest.) thanks -- PMM