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[54.240.197.234]) by smtp.gmail.com with ESMTPSA id y21sm492413edu.48.2020.03.25.11.09.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Mar 2020 11:09:44 -0700 (PDT) To: Jan Beulich References: <20200322161418.31606-1-julien@xen.org> <20200322161418.31606-4-julien@xen.org> <80c98b3e-efa7-66e6-bd47-61bc0560f535@suse.com> From: Julien Grall Message-ID: <993d82aa-9f19-0b27-a562-53f4c9b2a7a4@xen.org> Date: Wed, 25 Mar 2020 18:09:43 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <80c98b3e-efa7-66e6-bd47-61bc0560f535@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Subject: Re: [Xen-devel] [PATCH 03/17] xen/mm: Move the MM types in a separate header X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Wei Liu , Andrew Cooper , Julien Grall , Ian Jackson , George Dunlap , xen-devel@lists.xenproject.org Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Hi Jan, On 25/03/2020 15:00, Jan Beulich wrote: > On 22.03.2020 17:14, julien@xen.org wrote: >> From: Julien Grall >> >> It is getting incredibly difficult to use typesafe GFN/MFN/PFN in the >> headers because of circular dependency. For instance, asm-x86/page.h >> cannot include xen/mm.h. >> >> In order to convert more code to use typesafe, the types are now moved >> in a separate header that requires only a few dependencies. > > We definitely need to do this, so thanks for investing the > time. I think though that we want to settle up front (and > perhaps record in a comment in the new header) what is or > is not suitable to go into the new header. After all you're > moving not just type definitions, but also simple helper > functions. I am expecting headers to use the typesafe helpers (such mfn_add) in the long term. So I would like the new header to contain the type definitions and any wrappers that would turn 'generic' operations safe. I am not entirely sure yet how to formalize the rules in the header. Any ideas? > >> --- a/xen/include/xen/mm.h >> +++ b/xen/include/xen/mm.h >> @@ -1,50 +1,7 @@ >> /****************************************************************************** >> * include/xen/mm.h >> * >> - * Definitions for memory pages, frame numbers, addresses, allocations, etc. >> - * >> * Copyright (c) 2002-2006, K A Fraser >> - * >> - * +---------------------+ >> - * Xen Memory Management >> - * +---------------------+ >> - * >> - * Xen has to handle many different address spaces. It is important not to >> - * get these spaces mixed up. The following is a consistent terminology which >> - * should be adhered to. >> - * >> - * mfn: Machine Frame Number >> - * The values Xen puts into its own pagetables. This is the host physical >> - * memory address space with RAM, MMIO etc. >> - * >> - * gfn: Guest Frame Number >> - * The values a guest puts in its own pagetables. For an auto-translated >> - * guest (hardware assisted with 2nd stage translation, or shadowed), gfn != >> - * mfn. For a non-translated guest which is aware of Xen, gfn == mfn. >> - * >> - * pfn: Pseudophysical Frame Number >> - * A linear idea of a guest physical address space. For an auto-translated >> - * guest, pfn == gfn while for a non-translated guest, pfn != gfn. >> - * >> - * dfn: Device DMA Frame Number (definitions in include/xen/iommu.h) >> - * The linear frame numbers of device DMA address space. All initiators for >> - * (i.e. all devices assigned to) a guest share a single DMA address space >> - * and, by default, Xen will ensure dfn == pfn. >> - * >> - * WARNING: Some of these terms have changed over time while others have been >> - * used inconsistently, meaning that a lot of existing code does not match the >> - * definitions above. New code should use these terms as described here, and >> - * over time older code should be corrected to be consistent. >> - * >> - * An incomplete list of larger work area: >> - * - Phase out the use of 'pfn' from the x86 pagetable code. Callers should >> - * know explicitly whether they are talking about mfns or gfns. >> - * - Phase out the use of 'pfn' from the ARM mm code. A cursory glance >> - * suggests that 'mfn' and 'pfn' are currently used interchangeably, where >> - * 'mfn' is the appropriate term to use. >> - * - Phase out the use of gpfn/gmfn where pfn/mfn are meant. This excludes >> - * the x86 shadow code, which uses gmfn/smfn pairs with different, >> - * documented, meanings. >> */ >> >> #ifndef __XEN_MM_H__ >> @@ -54,100 +11,11 @@ >> #include >> #include >> #include >> -#include >> #include >> +#include > > Is there anything left in the header here which requires the > explicit inclusion of xen/kernel.h? The header was introduced for the sole purpose of the typesafe version of the min/max helpers. So it should be possible to drop the include. I will have a look and remove it if we can. Cheers, -- Julien Grall