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 C9E65C678D4 for ; Mon, 6 Mar 2023 10:04:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230195AbjCFKEC (ORCPT ); Mon, 6 Mar 2023 05:04:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229652AbjCFKD6 (ORCPT ); Mon, 6 Mar 2023 05:03:58 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C2FA185 for ; Mon, 6 Mar 2023 02:03:56 -0800 (PST) Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4PVZ0j3vHPz6J6KM; Mon, 6 Mar 2023 18:03:49 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Mon, 6 Mar 2023 10:03:52 +0000 Date: Mon, 6 Mar 2023 10:03:52 +0000 From: Jonathan Cameron To: Ira Weiny CC: , Michael Tsirkin , Fan Ni , , , Alison Schofield , Michael Roth , Philippe =?ISO-8859-1?Q?Mathieu-Daud=E9?= , Dave Jiang , Markus Armbruster , "Daniel P . =?ISO-8859-1?Q?Berrang=E9?=" , Eric Blake , Mike Maslenkin , =?ISO-8859-1?Q?Marc-Andr=E9?= Lureau , Thomas Huth Subject: Re: [PATCH v4 6/6] hw/cxl: Add clear poison mailbox command support. Message-ID: <20230306100352.00004a51@Huawei.com> In-Reply-To: <6402e9787cad0_606a629499@iweiny-mobl.notmuch> References: <20230303150908.27889-1-Jonathan.Cameron@huawei.com> <20230303150908.27889-7-Jonathan.Cameron@huawei.com> <6402e9787cad0_606a629499@iweiny-mobl.notmuch> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100001.china.huawei.com (7.191.160.183) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On Fri, 3 Mar 2023 22:47:20 -0800 Ira Weiny wrote: > Jonathan Cameron wrote: > > Current implementation is very simple so many of the corner > > cases do not exist (e.g. fragmenting larger poison list entries) > > One coding style change at the bottom and I'm still hung up on that loop > logic... > > > > > Signed-off-by: Jonathan Cameron > > --- > > v4: > > - Fix off by one on check of edge of vmr (cut and paste from similar > > but long fixed in the volatile memory series) > > - Drop unnecessary overflow check. > > - Ensure that even in case of overflow we still delete the element > > replaced (in the hole punching case) > > --- > > hw/cxl/cxl-mailbox-utils.c | 77 +++++++++++++++++++++++++++++++++++++ > > hw/mem/cxl_type3.c | 36 +++++++++++++++++ > > include/hw/cxl/cxl_device.h | 1 + > > 3 files changed, 114 insertions(+) > > > > diff --git a/hw/cxl/cxl-mailbox-utils.c b/hw/cxl/cxl-mailbox-utils.c > > index 64a3f3c1bf..0b30307fa3 100644 > > --- a/hw/cxl/cxl-mailbox-utils.c > > +++ b/hw/cxl/cxl-mailbox-utils.c > > @@ -65,6 +65,7 @@ enum { > > MEDIA_AND_POISON = 0x43, > > #define GET_POISON_LIST 0x0 > > #define INJECT_POISON 0x1 > > + #define CLEAR_POISON 0x2 > > }; > > > > /* 8.2.8.4.5.1 Command Return Codes */ > > @@ -511,6 +512,80 @@ static CXLRetCode cmd_media_inject_poison(struct cxl_cmd *cmd, > > return CXL_MBOX_SUCCESS; > > } > > > > +static CXLRetCode cmd_media_clear_poison(struct cxl_cmd *cmd, > > + CXLDeviceState *cxl_dstate, > > + uint16_t *len) > > +{ > > + CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate); > > + CXLPoisonList *poison_list = &ct3d->poison_list; > > + CXLType3Class *cvc = CXL_TYPE3_GET_CLASS(ct3d); > > + struct clear_poison_pl { > > + uint64_t dpa; > > + uint8_t data[64]; > > + }; > > + CXLPoison *ent; > > + uint64_t dpa; > > + > > + struct clear_poison_pl *in = (void *)cmd->payload; > > + > > + dpa = ldq_le_p(&in->dpa); > > + if (dpa + 64 > cxl_dstate->mem_size) { > > + return CXL_MBOX_INVALID_PA; > > + } > > + > > + /* Always exit loop on entry removal so no need for safe variant */ > > Commenting this is nice but I don't think it is needed. > > > + QLIST_FOREACH(ent, poison_list, node) { > > + /* > > + * Test for contained in entry. Simpler than general case > > + * as clearing 64 bytes and entries 64 byte aligned > > + */ > > + if ((dpa < ent->start) || (dpa >= ent->start + ent->length)) { > > + continue; > > + } > > + /* Do accounting early as we know one will go away */ > > + ct3d->poison_list_cnt--; > > Sorry to get so hung up on this but while I think this code now works I > still think it is odd and will be an issue to maintain. > > FWIW I don't think we have to keep 'ent' in the list here... > > > + if (dpa > ent->start) { > > + CXLPoison *frag; > > + /* Cannot overflow as replacing existing entry */ > > + > > + frag = g_new0(CXLPoison, 1); > > + > > + frag->start = ent->start; > > + frag->length = dpa - ent->start; > > + frag->type = ent->type; > > + > > + QLIST_INSERT_HEAD(poison_list, frag, node); > > + ct3d->poison_list_cnt++; > > + } > > + if (dpa + 64 < ent->start + ent->length) { > > + CXLPoison *frag; > > + > > + if (ct3d->poison_list_cnt == CXL_POISON_LIST_LIMIT) { > > + cxl_set_poison_list_overflowed(ct3d); > > + } else { > > + frag = g_new0(CXLPoison, 1); > > + > > + frag->start = dpa + 64; > > + frag->length = ent->start + ent->length - frag->start; > > + frag->type = ent->type; > > + QLIST_INSERT_HEAD(poison_list, frag, node); > > + ct3d->poison_list_cnt++; > > + } > > + } > > + /* Any fragments have been added, free original entry */ > > + QLIST_REMOVE(ent, node); > > + g_free(ent); > > + break; > > + } > > Why not this? Fair enough. I think this is a case of code evolving to a state that is non optimal in the end so I'll refactor it to something like you have suggested. I think we caan simplify it further by dragging the cacheline clear up to before the list manipulation. > > ... > CXLPoison *ent, found = NULL; > > ... > QLIST_FOREACH(ent, poison_list, node) { > /* > * Test for contained in entry. Simpler than general case > * as clearing 64 bytes and entries are 64 byte aligned > */ > if ((dpa >= ent->start) && (dpa < ent->start + ent->length)) { > found = ent; > break; > } > } > > /* > * Do we even need 'found'? Or is ent null if not found? > * I'm not sure how QLIST's work. > */ > if (found) { > CXLPoison *frag; > > QLIST_REMOVE(found, node); > ct3d->poison_list_cnt--; > > /* If not clearing the start, create new beginning of range */ > if (dpa > found->start) { > frag = g_new0(CXLPoison, 1); > frag->start = found->start; > frag->length = dpa - found->start; > frag->type = found->type; > QLIST_INSERT_HEAD(poison_list, frag, node); > ct3d->poison_list_cnt++; > } > > /* If needed, and space available, create new end of range */ > if (dpa + 64 < found->start + found->length) { > if (ct3d->poison_list_cnt == CXL_POISON_LIST_LIMIT) { > cxl_set_poison_list_overflowed(ct3d); > } else { > frag = g_new0(CXLPoison, 1); > > frag->start = dpa + 64; > frag->length = found->start + found->length - frag->start; > frag->type = found->type; > QLIST_INSERT_HEAD(poison_list, frag, node); > ct3d->poison_list_cnt++; > } > } > g_free(found); > } > ... > > > + /* Clearing a region with no poison is not an error so always do so */ > > + if (cvc->set_cacheline) > > For QEMU coding style you still need '{' '}'. Gah. > > Ira Thanks, Jonathan