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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6ADBAC7EE23 for ; Wed, 31 May 2023 14:25:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233175AbjEaOZo (ORCPT ); Wed, 31 May 2023 10:25:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40150 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237761AbjEaOZk (ORCPT ); Wed, 31 May 2023 10:25:40 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B16A7E2 for ; Wed, 31 May 2023 07:25:38 -0700 (PDT) Received: from dggpemm500006.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4QWWgd4jvFzLq8l; Wed, 31 May 2023 22:22:37 +0800 (CST) Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Wed, 31 May 2023 22:25:36 +0800 Subject: Re: [PATCH 6/6] kexec: enable kexec_crash_size to support two crash kernel regions To: Baoquan He CC: Eric Biederman , , , Michael Holzheu , Andrew Morton References: <20230527123439.772-1-thunder.leizhen@huawei.com> <20230527123439.772-7-thunder.leizhen@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: <955d2ba6-2cb8-7ee1-031f-e9033b32a3c8@huawei.com> Date: Wed, 31 May 2023 22:25:36 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/5/31 17:53, Baoquan He wrote: > On 05/27/23 at 08:34pm, Zhen Lei wrote: >> The crashk_low_res should be considered by /sys/kernel/kexec_crash_size >> to support two crash kernel regions. Since crashk_res manages the memory >> with high address and crashk_low_res manages the memory with low address, >> crashk_low_res is shrunken only when all crashk_res is shrunken. And >> because when there is only one crash kernel region, crashk_res is always >> used. Therefore, if all crashk_res is shrunken and crashk_low_res still >> exists, swap them. > > This looks good, otherwise someone else won't stop attempting to add > support of crashk_low_res shrinking. Not sure if this will bring corner > case issue in testing, let's see. For the patch log, I tried to > rephrase, feel free to refer to. > > ===== > The crashk_low_res should be considered by /sys/kernel/kexec_crash_size > to support two crash kernel regions shrinking if existing. > > While doing it, crashk_low_res will only be shrunk when the entire > crashk_res is empty; and if the crashk_res is empty and crahk_low_res > is not, change crashk_low_res to be crashk_res. > ===== > > With the log updated, you can add: > > Acked-by: Baoquan He OK, I will update the log and add Acked-by in v2. > >> >> Signed-off-by: Zhen Lei >> --- >> kernel/kexec_core.c | 43 ++++++++++++++++++++++++++++++++++++++----- >> 1 file changed, 38 insertions(+), 5 deletions(-) >> >> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c >> index e82bc6d6634136a..c1d50f6566300d9 100644 >> --- a/kernel/kexec_core.c >> +++ b/kernel/kexec_core.c >> @@ -1091,6 +1091,11 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs) >> } >> } >> >> +static inline resource_size_t crash_resource_size(const struct resource *res) >> +{ >> + return !res->end ? 0 : resource_size(res); >> +} >> + >> ssize_t crash_get_memory_size(void) >> { >> ssize_t size = 0; >> @@ -1098,8 +1103,8 @@ ssize_t crash_get_memory_size(void) >> if (!kexec_trylock()) >> return -EBUSY; >> >> - if (crashk_res.end != crashk_res.start) >> - size = resource_size(&crashk_res); >> + size += crash_resource_size(&crashk_res); >> + size += crash_resource_size(&crashk_low_res); >> >> kexec_unlock(); >> return size; >> @@ -1135,7 +1140,7 @@ int __crash_shrink_memory(struct resource *old_res, unsigned long new_size) >> int crash_shrink_memory(unsigned long new_size) >> { >> int ret = 0; >> - unsigned long old_size; >> + unsigned long old_size, low_size; >> >> if (!kexec_trylock()) >> return -EBUSY; >> @@ -1144,14 +1149,42 @@ int crash_shrink_memory(unsigned long new_size) >> ret = -ENOENT; >> goto unlock; >> } >> - old_size = !crashk_res.end ? 0 : resource_size(&crashk_res); >> + >> + low_size = crash_resource_size(&crashk_low_res); >> + old_size = crash_resource_size(&crashk_res) + low_size; >> new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN); >> if (new_size >= old_size) { >> ret = (new_size == old_size) ? 0 : -EINVAL; >> goto unlock; >> } >> >> - ret = __crash_shrink_memory(&crashk_res, new_size); >> + /* >> + * (low_size > new_size) implies that low_size is greater than zero. >> + * This also means that if low_size is zero, the else branch is taken. >> + * >> + * If low_size is greater than 0, (low_size > new_size) indicates that >> + * crashk_low_res also needs to be shrunken. Otherwise, only crashk_res >> + * needs to be shrunken. >> + */ >> + if (low_size > new_size) { >> + ret = __crash_shrink_memory(&crashk_res, 0); >> + if (ret) >> + goto unlock; >> + >> + ret = __crash_shrink_memory(&crashk_low_res, new_size); >> + } else { >> + ret = __crash_shrink_memory(&crashk_res, new_size - low_size); >> + } >> + >> + /* Swap crashk_res and crashk_low_res if needed */ >> + if (!crashk_res.end && crashk_low_res.end) { >> + crashk_res.start = crashk_low_res.start; >> + crashk_res.end = crashk_low_res.end; >> + release_resource(&crashk_low_res); >> + crashk_low_res.start = 0; >> + crashk_low_res.end = 0; >> + insert_resource(&iomem_resource, &crashk_res); >> + } >> >> unlock: >> kexec_unlock(); >> -- >> 2.25.1 >> > > . > -- Regards, Zhen Lei