From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Tiejun" Subject: Re: [RFC][v3][PATCH 1/6] xen:x86: record RMRR mappings Date: Tue, 19 Aug 2014 10:14:43 +0800 Message-ID: <53F2B313.5010408@intel.com> References: <1408091238-18364-1-git-send-email-tiejun.chen@intel.com> <1408091238-18364-2-git-send-email-tiejun.chen@intel.com> <53EDD539.90403@citrix.com> <53EE436502000078000BA911@mail.emea.novell.com> <53F1AE4C.5050002@intel.com> <53F1CE0D.7080005@citrix.com> <53F2003B02000078000BAAC3@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53F2003B02000078000BAAC3@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich , andrew.cooper3@citrix.com Cc: kevin.tian@intel.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org, yang.z.zhang@intel.com List-Id: xen-devel@lists.xenproject.org On 2014/8/18 20:31, Jan Beulich wrote: >>>>> Andrew Cooper 08/18/14 11:57 AM >>> >> On 18/08/14 08:42, Chen, Tiejun wrote: >>> On 2014/8/16 0:29, Jan Beulich wrote: >>>>>>> On 15.08.14 at 11:39, wrote: >>>>>> --- a/xen/include/asm-x86/e820.h >>>>>> +++ b/xen/include/asm-x86/e820.h >>>>>> @@ -23,6 +23,8 @@ struct e820map { >>>>>> struct e820entry map[E820MAX]; >>>>>> }; >>>>>> >>>>>> +typedef struct e820map rmrr_maps_t; >>>>> >>>>> This type is a single map of RMRR regions, not multiple maps. >>>>> rmrr_map_t please. >>>> >>>> ... this once again stresses what I stated previously: Piggybacking >>>> on the E820 handling here is just the wrong approach. There's >>>> really no correlation with E820 other than us wanting to use the >>>> gathered information for (among other things) adjusting the guest >>>> E820 table. But that doesn't in any way require any re-use of >>>> non-suitable data structures. >>> >>> Why are you saying this is not suitable? >>> >>> We need a structure to represent a RMRR entry including three fields, >>> start, size and type, and especially, essentially RMRR entry belongs >>> to e820 table as one entry. >> >> Not in Xen. Only as reported to guests, in which case an e820-like >> structure is most appropriate. > > E280-like yes, but ... > >>>> In fact I don't see the need for this first patch anyway, as RMRRs >>>> are already being put on a linked list as they get found. I.e. the >>> >>> Yes, that list, acpi_rmrr_unit, can be exposed here. But before you >>> copy to guest, don't you need to grab those fields from that list then >>> convert them as a suitable structure (mostly this is still same as >>> ) to be copied into a buffer? >> >> Yes, but the hypercall handler can do this which avoids all need to >> store an intermediate representation in Xen. >> >> list_for_each_entry(rmrr, &acpi_rmrr_units, list) >> { > >e820entry e; >> > >e.start = ... >> > >copy_to_guest_offset(... >> } > > ... as said before, I don't think using the E820 structure as-is is the right > approach: Neither do we need byte-granular fields, nor do we need a type > here. > Please don't say simply that e820entry is not suitable, what's your preferred structure here? Looks you are saying something like, struct __packed rmrr_entry { uint64_t addr; uint64_t size; }; but compare that to the existing e820entry, struct __packed e820entry { uint64_t addr; uint64_t size; uint32_t type; }; Anyway, please show me your ideal structure then I'd like to follow-up that since it's no big deal. Thanks Tiejun