From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh Subject: Re: [PATCH v6 04/10] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages Date: Mon, 16 Mar 2020 09:30:24 +0100 Message-ID: <20200316083024.GA3204377@kroah.com> References: <1584200119-18594-1-git-send-email-mikelley@microsoft.com> <1584200119-18594-5-git-send-email-mikelley@microsoft.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Arnd Bergmann Cc: Michael Kelley , Will Deacon , Ard Biesheuvel , Catalin Marinas , Mark Rutland , Marc Zyngier , Linux ARM , "linux-kernel@vger.kernel.org" , linux-hyperv@vger.kernel.org, linux-efi , linux-arch , olaf@aepfle.de, Andy Whitcroft , Vitaly Kuznetsov , Jason Wang , marcelo.cerri@canonical.com, "K. Y. Srinivasan" , sunilmut@microsoft.com, Boqun Feng List-Id: linux-arch.vger.kernel.org On Mon, Mar 16, 2020 at 09:22:43AM +0100, Arnd Bergmann wrote: > On Sat, Mar 14, 2020 at 4:36 PM Michael Kelley wrote: > > /* > > + * Functions for allocating and freeing memory with size and > > + * alignment HV_HYP_PAGE_SIZE. These functions are needed because > > + * the guest page size may not be the same as the Hyper-V page > > + * size. We depend upon kmalloc() aligning power-of-two size > > + * allocations to the allocation size boundary, so that the > > + * allocated memory appears to Hyper-V as a page of the size > > + * it expects. > > + * > > + * These functions are used by arm64 specific code as well as > > + * arch independent Hyper-V drivers. > > + */ > > + > > +void *hv_alloc_hyperv_page(void) > > +{ > > + BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE); > > + return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL); > > +} > > +EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page); > > I don't think there is any guarantee that kmalloc() returns page-aligned > allocations in general. How about using get_free_pages() > to implement this? Even if it was guaranteed, a pointless wrapper like this is not needed or ok, and shouldn't be created, just use kmalloc. thanks, greg k-h 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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 3F101C18E5B for ; Mon, 16 Mar 2020 08:30:36 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 9FDB620658 for ; Mon, 16 Mar 2020 08:30:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="FEUAIPo/"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="aO/QdzZI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FDB620658 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=zTwoLv8W/IV/3/voIaHdJnMvoxiRWbOG9rfL0BqKZdI=; b=FEUAIPo/MP7YNk 5CK9zrE2xSap5/LpaURhF1+Fzx2IuAoAiYTapbwg82uOhQ6DVyeWFk+n6wi81m+4ph+xJWhkmiaLK bu6RVUJafNR5BUFA/k4eO7Y38X4SQocE5+PbjSZ/XH08fXFwqkxCkRn6ZAkITbl+xGYk2FbdT3Laq g2KjRRhOnUj0pvPMQVK9ZTUuFe0uDSwXky6pZ7ZYnwfIuBuXtpQmOoYxXo8i3ps3kyO4uaiEvERTQ r1BnJXv70UX9kHYr7A+BbWmAuagFwAEyAzolhHjK3t8awY9R4X/vwp+INb3DMJLHwyTtuJ4WC2vOm wtUB6cEz12+QuSSfL4AA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jDl8p-0007qm-MU; Mon, 16 Mar 2020 08:30:31 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jDl8k-0007oq-Ny for linux-arm-kernel@lists.infradead.org; Mon, 16 Mar 2020 08:30:28 +0000 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C03CF20658; Mon, 16 Mar 2020 08:30:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584347426; bh=GJ8GsEypd+i+4W9htj3qLpzQtn+OsOQ9mGSyV2/R7dA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=aO/QdzZIFo1XvwNhvNiWRREapqKvMl1JtbC2hByDGtwxxWiPLc8FMNy1H3SN2m+Lv HrJyKp++eqtMyv7/6pUJ4mP2NYJy9OfRPytBOLRGsbhN+9dElVQQ92E7u4rwZ03INc K2y4pim3uAIqEEP/OBj07CjTShjFfqgLzx2t7lM4= Date: Mon, 16 Mar 2020 09:30:24 +0100 From: gregkh To: Arnd Bergmann Subject: Re: [PATCH v6 04/10] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages Message-ID: <20200316083024.GA3204377@kroah.com> References: <1584200119-18594-1-git-send-email-mikelley@microsoft.com> <1584200119-18594-5-git-send-email-mikelley@microsoft.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200316_013026_824417_19696FE3 X-CRM114-Status: GOOD ( 15.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-arch , linux-hyperv@vger.kernel.org, linux-efi , Boqun Feng , Catalin Marinas , Jason Wang , sunilmut@microsoft.com, "linux-kernel@vger.kernel.org" , Michael Kelley , marcelo.cerri@canonical.com, olaf@aepfle.de, Marc Zyngier , Andy Whitcroft , Vitaly Kuznetsov , "K. Y. Srinivasan" , Will Deacon , Ard Biesheuvel , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Mar 16, 2020 at 09:22:43AM +0100, Arnd Bergmann wrote: > On Sat, Mar 14, 2020 at 4:36 PM Michael Kelley wrote: > > /* > > + * Functions for allocating and freeing memory with size and > > + * alignment HV_HYP_PAGE_SIZE. These functions are needed because > > + * the guest page size may not be the same as the Hyper-V page > > + * size. We depend upon kmalloc() aligning power-of-two size > > + * allocations to the allocation size boundary, so that the > > + * allocated memory appears to Hyper-V as a page of the size > > + * it expects. > > + * > > + * These functions are used by arm64 specific code as well as > > + * arch independent Hyper-V drivers. > > + */ > > + > > +void *hv_alloc_hyperv_page(void) > > +{ > > + BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE); > > + return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL); > > +} > > +EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page); > > I don't think there is any guarantee that kmalloc() returns page-aligned > allocations in general. How about using get_free_pages() > to implement this? Even if it was guaranteed, a pointless wrapper like this is not needed or ok, and shouldn't be created, just use kmalloc. thanks, greg k-h _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel