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: Received: from mail.kernel.org ([198.145.29.99]:53400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730016AbgCPIa2 (ORCPT ); Mon, 16 Mar 2020 04:30:28 -0400 Date: Mon, 16 Mar 2020 09:30:24 +0100 From: gregkh 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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: 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 Message-ID: <20200316083024.jBizwS2SyqAS5qNmIYbRrI-F75pQ4OzkCdRUMMNKpSE@z> 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