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 96F74C3DA4A for ; Mon, 29 Jul 2024 16:51:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=+cXxOiDKrFT9b5NlMgR7bH2wonHbOte3VUO2//bA1jM=; b=fgpt8+RYqXSbzhGVs1eJltsWkG MbYoplJyQ58aJqAb3BH7s/Njbb3bPXz7XBU1MMhcn0EMAo33muY/mIZhXpy9CdYojoXugV11+onUs XIFL+TAwM5mU5tSwpjZle69DnhTlz5OJSlocSbZnhNNI5rVTOuZ+kygT4Vlnq6qwv0FaAs1SuTR+q vXIyLjZW0/MWCbjW89s6eYfQHxAsrHd6D7Bh8ZV1RZ6g8+fsA8vpZ6w4WHMMmW/EfeMoiJXbG+iwS W4IkBWcytMHXlDAp6ZcGBXkQKzVjWMWegq/q7MMyD/20nDS5qjdDuEUgDhfN/QB/LkDIQ51zPFVCS N1r5JekA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sYTaw-0000000C8Cg-4Agn; Mon, 29 Jul 2024 16:51:34 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sYTaU-0000000C85f-13LZ for linux-arm-kernel@lists.infradead.org; Mon, 29 Jul 2024 16:51:08 +0000 Received: from [10.137.186.190] (unknown [131.107.159.62]) by linux.microsoft.com (Postfix) with ESMTPSA id 576B620B7165; Mon, 29 Jul 2024 09:51:04 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 576B620B7165 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1722271864; bh=+cXxOiDKrFT9b5NlMgR7bH2wonHbOte3VUO2//bA1jM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=cAnu5aOEkHh7wxXbogTb1Cop95sAfjfbO6Fw31tIR4cHaVDOUVNcmci5CV+FTodxU 2hFQZTn0VXTMRnbETa7vKc9SRTH3mFJ8pocSP9iggoq5Wp3rZGswCxndPgnRoMD0px 8uhorG0O/RjITxfLaGDscHaSu2QcqX6qnqfiH1uM= Message-ID: Date: Mon, 29 Jul 2024 09:51:07 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 6/7] Drivers: hv: vmbus: Get the IRQ number from DT To: Arnd Bergmann , Krzysztof Kozlowski , bhelgaas@google.com, Borislav Petkov , Catalin Marinas , Dave Hansen , Dexuan Cui , Haiyang Zhang , "H. Peter Anvin" , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , "K. Y. Srinivasan" , Len Brown , Lorenzo Pieralisi , Ingo Molnar , "Rafael J . Wysocki" , Rob Herring , Thomas Gleixner , Wei Liu , Will Deacon , linux-acpi@vger.kernel.org, Linux-Arch , linux-arm-kernel@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org Cc: apais@microsoft.com, benhill@microsoft.com, ssengar@microsoft.com, sunilmut@microsoft.com, vdso@hexbites.dev References: <20240726225910.1912537-1-romank@linux.microsoft.com> <20240726225910.1912537-7-romank@linux.microsoft.com> <7418bfcd-c572-4574-accc-7f2ae117529f@kernel.org> Content-Language: en-US From: Roman Kisel In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240729_095106_478900_F62F537E X-CRM114-Status: GOOD ( 23.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/27/2024 2:17 AM, Arnd Bergmann wrote: > On Sat, Jul 27, 2024, at 10:56, Krzysztof Kozlowski wrote: >> On 27/07/2024 00:59, Roman Kisel wrote: >>> @@ -2338,6 +2372,21 @@ static int vmbus_device_add(struct platform_device *pdev) >>> cur_res = &res->sibling; >>> } >>> >>> + /* >>> + * Hyper-V always assumes DMA cache coherency, and the DMA subsystem >>> + * might default to 'not coherent' on some architectures. >>> + * Avoid high-cost cache coherency maintenance done by the CPU. >>> + */ >>> +#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ >>> + defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \ >>> + defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) >>> + >>> + if (!of_property_read_bool(np, "dma-coherent")) >>> + pr_warn("Assuming cache coherent DMA transactions, no 'dma-coherent' node supplied\n"); >> >> Why do you need this property at all, if it is allways dma-coherent? Are >> you supporting dma-noncoherent somewhere? > > It's just a sanity check that the DT is well-formed. > > Since the dma-coherent property is interpreted by common code, it's > not up to hv to change the default for the platform. I'm not sure > if the presence of CONFIG_ARCH_HAS_SYNC_DMA_* options is the correct > check to determine that an architecture defaults to noncoherent > though, as the function may be needed to do something else. I used the ifdef as the dma_coherent field is declared under these macros: #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) extern bool dma_default_coherent; static inline bool dev_is_dma_coherent(struct device *dev) { return dev->dma_coherent; } #else #define dma_default_coherent true static inline bool dev_is_dma_coherent(struct device *dev) { return true; } i.e., there is no API to set dma_coherent. As I see it, the options are either warn the user if they forgot to add `dma-coherent` if (!dev_is_dma_coherent(dev)) pr_warn("add dma-coherent to be faster\n"), or warn and force the flag to true. Maybe just warn the user I think now... The code will be cleaner (no need to emulate a-would-be set_dma_coherent) , and the user will know how to make the system perform at its best. Appreciate sharing the reservations about that piece! > > The global "dma_default_coherent' may be a better thing to check > for. This is e.g. set on powerpc64, riscv and on specific mips > platforms, but it's never set on arm64 as far as I can tell. > > Arnd -- Thank you, Roman