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 D9393C433EF for ; Sat, 22 Jan 2022 03:46:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231985AbiAVDqF (ORCPT ); Fri, 21 Jan 2022 22:46:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53446 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231754AbiAVDqE (ORCPT ); Fri, 21 Jan 2022 22:46:04 -0500 Received: from mail-yb1-xb2b.google.com (mail-yb1-xb2b.google.com [IPv6:2607:f8b0:4864:20::b2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7692DC06173D for ; Fri, 21 Jan 2022 19:46:04 -0800 (PST) Received: by mail-yb1-xb2b.google.com with SMTP id o80so33206831yba.6 for ; Fri, 21 Jan 2022 19:46:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=atishpatra.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GK+DRe45zgKVXKFo8gPG6uGiKgyXp2cTD0RJLmCvZSY=; b=QGr+ig/1NkNSQ/DVpGfdNvXcytkEpcUB2Z3Lt1CjofEcwFvFzBHGWU/x6bjfbD+BJM 28sNmiu9uZQkQfT183g4IwINmBs6qBDPjmUX9tPWIkCpWWqqVLq8KPBLi/4G28cYL2Qc XGeEdtOfShkYp+2YRobhPxXvQANlnoodCC1rs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GK+DRe45zgKVXKFo8gPG6uGiKgyXp2cTD0RJLmCvZSY=; b=Gz6/qoo4IGscTKcWeVzy1awheirQa/8gTtG0KNoyawlENmFw8UMqd5k2PiHYkqTWjZ Hn7wgE1kjrXTzbm3zwPnIci0nrLv592ZF5l6n694vLxzHzXV3iUyK75cXFsmy++vmz2Z KaVNDG3/1dlRNZIXRIE/mzXRNVsSp//WBtn0Q5N92hlBVPFXqRzP4SefIzA/q+hLjIOw jPqYBuW7VdpkmoDig6O4Ml/Kzra3I7Be9xH8BaYo4twjkaq++UieDU6mzFy/MZ3RVgUo 4hDp/18wvZ7whQsJTmZ7RJpNLslLy1VS//sFdPtLLJEtEqxZX5CMzBbf7k1ZDHP9UT6N Uf3g== X-Gm-Message-State: AOAM531Kryw32LpWOzQVK3Rb9Ognuwy+valoR+JaUITWoIqCeukkesbB bK3F0JTIEBREiiAAay/m2YSWMZSriPBoxYJcGUVQ X-Google-Smtp-Source: ABdhPJxqUxGbofs9AyGZqKNuQHUzAvH8Oar5nZINBL0NQkR2tr89y472EbgCFBjmW5/Z2aBrOhhnBxjAZN3ITVL7G/c= X-Received: by 2002:a25:b852:: with SMTP id b18mr10998199ybm.651.1642823163252; Fri, 21 Jan 2022 19:46:03 -0800 (PST) MIME-Version: 1.0 References: <20220121163618.351934-1-heiko@sntech.de> <20220121163618.351934-2-heiko@sntech.de> In-Reply-To: <20220121163618.351934-2-heiko@sntech.de> From: Atish Patra Date: Fri, 21 Jan 2022 19:45:52 -0800 Message-ID: Subject: Re: [PATCH v5 01/14] riscv: only use IPIs to handle cache-flushes on remote cpus To: Heiko Stuebner Cc: Palmer Dabbelt , Paul Walmsley , Albert Ou , linux-riscv , devicetree , "linux-kernel@vger.kernel.org List" , Rob Herring , Wei Fu , liush , Guo Ren , Anup Patel , Drew Fustini , Christoph Hellwig , Arnd Bergmann , Chen-Yu Tsai , Maxime Ripard , Daniel Lustig , Greg Favor , Andrea Mondelli , Jonathan Behrens , Xinhaoqu , Bill Huffman , Nick Kossifidis , Allen Baum , Josh Scheid , Richard Trauben , Samuel Holland , Christoph Muellner , Philipp Tomsich Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 21, 2022 at 8:37 AM Heiko Stuebner wrote: > > Right now, the flush_icache functions always use the SBI remote-fence > when SBI is available, leaving using IPIs as a fallback mechanism. > > IPIs on the other hand are more flexible, as the ipi_ops are initially > set to go through SBI but later will be overwritten to go through the > ACLINT/CLINT. > > In a discussion we had, Nick was of the opinion that "In general we > should prefer doing IPIs on S-mode through CLINT instead of going > through SBI/M-mode, Yes. Once Anup's ACLINT drivers are merged, that should be the preferred approach. https://github.com/avpatel/linux/commit/416c667fd77d6f1fc310cbf727ec127aaf96cae2 >so IMHO we should only be using > on_each_cpu_mask(ipi_remote_fence_i) on flush_icache_all()/ > flush_icache_mm() and remove any explicit calls to sbi_remote_fence_i(), That's a bit confusing because we will be using SBI calls for all other fences while using IPIs for fence.i > because this way we continue using SBI for doing remote fences even after > CLINT/ACLINT driver is registered, instead of using direct IPIs through > CLINT/ACLINT." > > So follow this suggestion and just do ipi calls to have the proper kernel > parts do them, > > This also fixes the null-ptr dereference happening when flush_icache_all() > is called before sbi_init(). > IMHO, this series should only fix the null-ptr dereference issue. The IPI based fence (for all) should only be disabled along with the ACLINT driver that actually enables S-mode IPIs. > Suggested-by: Nick Kossifidis > Signed-off-by: Heiko Stuebner > --- > arch/riscv/mm/cacheflush.c | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) > > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c > index 6cb7d96ad9c7..c35375cd52ec 100644 > --- a/arch/riscv/mm/cacheflush.c > +++ b/arch/riscv/mm/cacheflush.c > @@ -17,11 +17,7 @@ static void ipi_remote_fence_i(void *info) > void flush_icache_all(void) > { > local_flush_icache_all(); > - > - if (IS_ENABLED(CONFIG_RISCV_SBI)) > - sbi_remote_fence_i(NULL); > - else > - on_each_cpu(ipi_remote_fence_i, NULL, 1); > + on_each_cpu(ipi_remote_fence_i, NULL, 1); > } > EXPORT_SYMBOL(flush_icache_all); > > @@ -66,8 +62,6 @@ void flush_icache_mm(struct mm_struct *mm, bool local) > * with flush_icache_deferred(). > */ > smp_mb(); > - } else if (IS_ENABLED(CONFIG_RISCV_SBI)) { > - sbi_remote_fence_i(&others); > } else { > on_each_cpu_mask(&others, ipi_remote_fence_i, NULL, 1); > } > -- > 2.30.2 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv -- Regards, Atish 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9F212C433F5 for ; Sat, 22 Jan 2022 03:46:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; 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Fri, 21 Jan 2022 19:46:03 -0800 (PST) MIME-Version: 1.0 References: <20220121163618.351934-1-heiko@sntech.de> <20220121163618.351934-2-heiko@sntech.de> In-Reply-To: <20220121163618.351934-2-heiko@sntech.de> From: Atish Patra Date: Fri, 21 Jan 2022 19:45:52 -0800 Message-ID: Subject: Re: [PATCH v5 01/14] riscv: only use IPIs to handle cache-flushes on remote cpus To: Heiko Stuebner Cc: Palmer Dabbelt , Paul Walmsley , Albert Ou , linux-riscv , devicetree , "linux-kernel@vger.kernel.org List" , Rob Herring , Wei Fu , liush , Guo Ren , Anup Patel , Drew Fustini , Christoph Hellwig , Arnd Bergmann , Chen-Yu Tsai , Maxime Ripard , Daniel Lustig , Greg Favor , Andrea Mondelli , Jonathan Behrens , Xinhaoqu , Bill Huffman , Nick Kossifidis , Allen Baum , Josh Scheid , Richard Trauben , Samuel Holland , Christoph Muellner , Philipp Tomsich X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220121_194605_592552_CFFBE4F7 X-CRM114-Status: GOOD ( 25.99 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Fri, Jan 21, 2022 at 8:37 AM Heiko Stuebner wrote: > > Right now, the flush_icache functions always use the SBI remote-fence > when SBI is available, leaving using IPIs as a fallback mechanism. > > IPIs on the other hand are more flexible, as the ipi_ops are initially > set to go through SBI but later will be overwritten to go through the > ACLINT/CLINT. > > In a discussion we had, Nick was of the opinion that "In general we > should prefer doing IPIs on S-mode through CLINT instead of going > through SBI/M-mode, Yes. Once Anup's ACLINT drivers are merged, that should be the preferred approach. https://github.com/avpatel/linux/commit/416c667fd77d6f1fc310cbf727ec127aaf96cae2 >so IMHO we should only be using > on_each_cpu_mask(ipi_remote_fence_i) on flush_icache_all()/ > flush_icache_mm() and remove any explicit calls to sbi_remote_fence_i(), That's a bit confusing because we will be using SBI calls for all other fences while using IPIs for fence.i > because this way we continue using SBI for doing remote fences even after > CLINT/ACLINT driver is registered, instead of using direct IPIs through > CLINT/ACLINT." > > So follow this suggestion and just do ipi calls to have the proper kernel > parts do them, > > This also fixes the null-ptr dereference happening when flush_icache_all() > is called before sbi_init(). > IMHO, this series should only fix the null-ptr dereference issue. The IPI based fence (for all) should only be disabled along with the ACLINT driver that actually enables S-mode IPIs. > Suggested-by: Nick Kossifidis > Signed-off-by: Heiko Stuebner > --- > arch/riscv/mm/cacheflush.c | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) > > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c > index 6cb7d96ad9c7..c35375cd52ec 100644 > --- a/arch/riscv/mm/cacheflush.c > +++ b/arch/riscv/mm/cacheflush.c > @@ -17,11 +17,7 @@ static void ipi_remote_fence_i(void *info) > void flush_icache_all(void) > { > local_flush_icache_all(); > - > - if (IS_ENABLED(CONFIG_RISCV_SBI)) > - sbi_remote_fence_i(NULL); > - else > - on_each_cpu(ipi_remote_fence_i, NULL, 1); > + on_each_cpu(ipi_remote_fence_i, NULL, 1); > } > EXPORT_SYMBOL(flush_icache_all); > > @@ -66,8 +62,6 @@ void flush_icache_mm(struct mm_struct *mm, bool local) > * with flush_icache_deferred(). > */ > smp_mb(); > - } else if (IS_ENABLED(CONFIG_RISCV_SBI)) { > - sbi_remote_fence_i(&others); > } else { > on_each_cpu_mask(&others, ipi_remote_fence_i, NULL, 1); > } > -- > 2.30.2 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv -- Regards, Atish _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv