From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: sources of freebsd with xen-4.2 kernel updates Date: Mon, 30 Dec 2013 09:52:43 -0500 Message-ID: <20131230145243.GA14189@phenom.dumpdata.com> References: <52C12A5D.3030409@citrix.com> <6BFA750A-977E-4119-BC97-594754C42CE3@gmail.com> <52C15844.6050309@citrix.com> <3D73274A-8C14-49BF-8DF3-27CE840CC275@gmail.com> <20131230124221.GA14746@zion.uk.xensource.com> <52C16CAD.4040009@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <52C16CAD.4040009@citrix.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: Roger Pau =?iso-8859-1?Q?Monn=E9?= Cc: Igor Kozhukhov , Wei Liu , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Mon, Dec 30, 2013 at 01:53:01PM +0100, Roger Pau Monn=E9 wrote: > On 30/12/13 13:42, Wei Liu wrote: > > On Mon, Dec 30, 2013 at 04:18:28PM +0400, Igor Kozhukhov wrote: > >> > >> On Dec 30, 2013, at 3:25 PM, Roger Pau Monn=E9 wrote: > >> > >>> On 30/12/13 11:57, Igor Kozhukhov wrote: > >>>> Hi Roger, > >>>> > >>>> thanks for the link. > >>>> I have the same/(similar the same) implementation on illumos(OpenSol= aris). > >>>> > >>>> do you have plans for grant table v1 & v2 implementation on FreeBSD ? > >>> > >>> Grant table v1 is the current implementation, and I don't have plans > >>> currently to add support for v2 (cannot speak of others though). > >>> > >>> Linux has v2 implemented, but AFAIK there's no user of the new featur= es > >>> introduced by v2. Right now with v2 you just end up with less grants, > >>> because v2 grants metadata use twice as much memory as v1 grants, and > >>> the number of grant frames is limited by the hypervisor. > >>> > >> Thanks for your info. > >> > >> Could you please let me know - can we use v1 for PV and HVM guests ? > >> I looked v2 implementation on Linux and found that v1 is using for HVM= , and v2 for PV - but maybe i'm wrong. > >> > > = > > You can use V1 for all guests for sure. > > = > > My understanding is that the code in Linux's grant-table.c requests V2 > > form the hypervisor, but it will fall back to using V1 if V2 is not > > avaiable. > = > Linux explicitly requests v1 when running as an HVM guest (I have no > idea why), for the rest it tries v2 first and falls back to v1 if B/c it did not have the code to support mapping of the status page: commit 69e8f430e243d657c2053f097efebc2e2cd559f0 Author: Konrad Rzeszutek Wilk Date: Wed Jan 25 00:13:20 2012 -0500 xen/granttable: Disable grant v2 for HVM domains. = As proper scaffolding for supporting error status is not yet implemented. = BUG: unable to handle kernel NULL pointer dereference at 00000000000004= 00 IP: [] gnttab_end_foreign_access_ref_v2+0x29/0x40 PGD 32aa3067 PUD 32a87067 PMD 0 Oops: 0000 [#1] PREEMPT SMP CPU 0 Modules linked in: sg sr_mod cdrom ata_generic ata_piix libata scsi_mod= xen_blkfront xen_netfront fb_sys_fops sysimgblt sysfillr cmd = Pid: 2307, comm: ip Not tainted 3.3.0-rc1 #1 Xen HVM domU RIP: 0010:[] [] gnttab_end_foreign= _access_ref_v2+0x29/0x40 RSP: 0018:ffff88003be03d38 EFLAGS: 00010206 RAX: 0000000000000000 RBX: ffff880033210640 RCX: 0000000000000040 RDX: 0000000000002000 RSI: 0000000000000000 RDI: 0000000000000200 RBP: ffff88003be03d38 R08: 0000000000000101 R09: 0000000000000000 R10: dead000000100100 R11: 0000000000000000 R12: ffff88003be03e48 R13: 0000000000000001 R14: ffff880039461c00 R15: 0000000000000200 FS: 00007fb1f84ec700(0000) GS:ffff88003be00000(0000) knlGS:00000000000= 00000 ... It should be implemented at some point.. but since there are no real users of V2 it is a the bottom of the pile of 'todo'. > there's no v2 support: > = > http://lxr.free-electrons.com/source/drivers/xen/grant-table.c#L1116 > = > As Wei points out, you can safely use v1 for all kind of guests, at > least on x86. > = > Roger. > = > = > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel