From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [RFC][v3][PATCH 1/6] xen:x86: record RMRR mappings Date: Mon, 18 Aug 2014 10:57:33 +0100 Message-ID: <53F1CE0D.7080005@citrix.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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <53F1AE4C.5050002@intel.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: "Chen, Tiejun" , Jan Beulich , ian.campbell@citrix.com, ian.jackson@eu.citrix.com, stefano.stabellini@eu.citrix.com, kevin.tian@intel.com, yang.z.zhang@intel.com Cc: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org 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: >>>> @@ -80,6 +81,18 @@ static int __init acpi_register_rmrr_unit(struct >>>> acpi_rmrr_unit *rmrr) >>>> return 0; >>>> } >>>> >>>> +/* Record RMRR mapping to ready expose VM. */ >>>> +static int __init rmrr_maps_register(struct acpi_rmrr_unit *rmrr) >>>> +{ >>> >>> You absolutely need some protection against calling this function more >>> than 128 times, or you need to do dynamic allocation of the storage. >> >> This together with ... >> >>>> --- 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. > >> >> 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 > e820entry) 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(... } But with appropriate error checking. ~Andrew