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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 D296BC0044D for ; Mon, 16 Mar 2020 08:30:52 +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 A1F0F20658 for ; Mon, 16 Mar 2020 08:30:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="oJuaSsk0"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="iljvpBfj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1F0F20658 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:To:From: Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=m0YXNnvnmXozhY3PTouofgQ7DoxtzE5NF7UrzIiVZQY=; b=oJuaSsk07iLlX8/kIJPUY6inZ t9htcMa+UBevgEnxoCrz6zaqYZgkPp/ABn+TETmV3uDBFPT04IQ/6rWtXxl4fgCAVknEjYDOr79zW fLkNibpd2CvGFZYVKyTJUt6pq0tbtNXhwFO8Yj5Z+C9ODeZ/K3QTz84p0dVC7enWM8VCg4ni9SXsx 9VJRzEv1KKGcgskNdom7J7vGdMEj6IG0FtSJdjo8wD5ZBEwE6LOueGEc+P5MkKTNjoo6EFVMNgxrf 6/lOq5ipx+HXCX4bIuPVP3A8GcLtUnoUE1XDKhlylR59OOY7twEEEih1MoNUPWWX37njekKs2gbbv nRljIIZSg==; 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 1jDl97-00085r-58; Mon, 16 Mar 2020 08:30:49 +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 1jDl93-00083o-3z for linux-arm-kernel@lists.infradead.org; Mon, 16 Mar 2020 08:30:46 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (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 A472820658; Mon, 16 Mar 2020 08:30:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584347444; bh=ShtIzAXjdARpIp5bk6R+u6x5+mPatLQqVE+H2TFyyiI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=iljvpBfjN2QMpa+akkgow4BQCj7qUXZxzO9BNLKJqukhpSaF5nQwMPp3dEN9PjoW1 3gBXFXuJUC19uMMOg7vzlyRrTuBNqoC9X/18UiBS5+4VMORwfPLMuJEm2R95vdqD7y wfoZd+uoGkyYhgnoSQySBYoJXMMLSO29tEYXU0Pk= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1jDl91-00D1aD-0w; Mon, 16 Mar 2020 08:30:43 +0000 MIME-Version: 1.0 Date: Mon, 16 Mar 2020 08:30:42 +0000 From: Marc Zyngier To: Arnd Bergmann Subject: Re: [PATCH v6 04/10] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages In-Reply-To: References: <1584200119-18594-1-git-send-email-mikelley@microsoft.com> <1584200119-18594-5-git-send-email-mikelley@microsoft.com> Message-ID: <632eb459dbe53a9b69df2a4f030a755b@kernel.org> X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/1.3.10 X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: arnd@arndb.de, mikelley@microsoft.com, will@kernel.org, ardb@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-efi@vger.kernel.org, linux-arch@vger.kernel.org, olaf@aepfle.de, apw@canonical.com, vkuznets@redhat.com, jasowang@redhat.com, marcelo.cerri@canonical.com, kys@microsoft.com, sunilmut@microsoft.com, boqun.feng@gmail.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200316_013045_202588_4993D977 X-CRM114-Status: GOOD ( 12.89 ) 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, gregkh , Andy Whitcroft , Vitaly Kuznetsov , "K. Y. Srinivasan" , Will Deacon , Ard Biesheuvel , Linux ARM Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-03-16 08:22, 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. I believe that guarantee came with 59bb47985c1db ("mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)"). > How about using get_free_pages() to implement this? This would certainly work, at the expense of a lot of wasted memory when PAGE_SIZE isn't 4k. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel