Re: [Xen-devel] [PATCH v2][RFC] libxl: Add AHCI support for upstream qemu

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 11/06/2015 12:28, Fabio Fantoni ha scritto:
> Il 11/06/2015 12:06, Zir Blazer ha scritto:
> > Since I'm not a developer I may be peeking my nose a bit too far, but 
> > based on what I know, I think that enabling AHCI by default would be 
> > a compatibility suicide. I'm not sure about Linux and Windows 
> > Vista/7/8+, but at least for Windows XP based VMs, it would be a 
> > terrible idea.
> Also use windows xp without security updates (support ended one year 
> ago) is a "suicide".
> I already did this patch considering windows domU problems (I'm using 
> mainly them for now), ahci used with option (ahci=0|1) instead replace 
> and default is disabled.
> I tried it with different windows (excluding xp...abandoned)
> I also tried with new winpv drivers 
> (http://www.xenproject.org/developers/teams/windows-pv-drivers.html)
> With this patch applied ahci will be not used and will be used only 
> setting ahci=1, is it a good idea or is there problem also in this case?
I did many other tests in different linux hvm domUs (fedora and ubuntu) 
and windows (7, 8.1, 10) without found problems.
Is this patch acceptable for xen 4.6?

> Thanks for any reply and sorry for my bad english.
>
> > Back during WXP years, the vanilla install ISO didn't had any AHCI 
> > Drivers integrated at all. If you set the SATA Controller to AHCI, 
> > the WXP installation wouldn't detect any Hard Disk at all. If you 
> > really wanted to use AHCI during its early days, you would need a 
> > Floppy Disk with the AHCI Drivers of your SATA Controller 
> > (Chipset/South Bridge or third party controller), that you could use 
> > by pressing the F6 key right after booting the install CD:
> > http://www.pc-tips-and-tricks.com/images/Install-windows-xp-02.jpg
> >
> > If you didn't had a Floppy Disk Driver or were lazy, the typical 
> > choice was to set the SATA Controller to IDE and install WXP, 
> > skipping anything AHCI related.
> > At some point an application called nLite appeared, which allowed you 
> > to make your custom Windows XP ISO. You could easily modify a lot of 
> > default options, integrate hotfixes, and even Drivers, and after you 
> > were happy with your changes, you could then make your custom ISO and 
> > burn it to a CD (Or from a USB Flash Drive with other tools to make 
> > it booteable). So, with nLite, it was rather easy to integrated the 
> > AHCI Drivers of your SATA Controller to the install ISO. This way, if 
> > you were doing a fresh install, reinstall or repair, there was no 
> > excuse to not use AHCI.
> > However, since for VM usage AHCI was not available at all until QEMU 
> > implemented it recently, by default you will be always using IDE, so 
> > there was no actual need to make a customized WXP install ISO with 
> > AHCI Drivers that you were never going to use. Besides, Windows XP 
> > doesn't even install nor have ready any AHCI Drivers if you're in IDE 
> > mode, so if you're going to switch to use AHCI by default, every 
> > existing WXP VM would greet you with a BSOD after upgrading Xen.
> >
> > So, with this proposal you would have two issues: First, doing a new 
> > install of Windows XP on a VM , since by default it shouldn't detect 
> > any HD at all in AHCI. Second, that existing WXP VMs will BSOD on 
> > boot. For as long as you can switch to IDE mode everything should 
> > still be working as always, but it would mean that at the very least 
> > you would have to modify the DomU config file to replace default AHCI 
> > with old IDE.
> > Regarding using Windows XP with AHCI:
> > First, as stated before, if you want to install it on a new VM, you 
> > need the AHCI Drivers. Since it seems that at some point support for 
> > Floppy Disk got removed from Xen (I tried recently to use a Floppy 
> > Disk image with fda= as stated somewhere on the wiki, but it did 
> > nothing. Nor I found any recent documentation claiming that you can 
> > mount a Floppy Disk image at all), the only choice is to make a 
> > custom ISO with nLite with the AHCI Drivers integrated in it. Since 
> > the emulated Southbridge is an Intel ICH9, I believe that the Drivers 
> > that should be needed are these:
> > http://www.win-raid.com/t22f23-Guide-Integration-of-Intels-AHCI-RAID-drivers-into-a-Windows-XP-W-k-W-k-CD.html 
> >
> > Check for the a) and c) options for WXP/2003 in 32 and 64 Bits variants.
> >
> > Also, it is important to note that the plain ICH9 Southbridge 
> > according to Intel DOES NOT OFFICIALLY HAVE AHCI SUPPORT, ICH9R does.
> > http://en.wikipedia.org/wiki/I/O_Controller_Hub#ICH9
> >
> > The previous Drivers are claimed to have been modified to force 
> > support for ICH9 since AHCI is there, just that the original Drivers 
> > doesn't want to use it. Typical artificial market segmentation 
> > strategies. Still, if QEMU is emulating the plain ICH9 and you can't 
> > get Windows to see drives in AHCI mode after integrating the AHCI 
> > Drivers, that may be why.
> >
> > Second, it is possible to switch from IDE to AHCI on WXP without 
> > reinstalling, but doing it is rather hacky and instructions are very 
> > Chipset and vendor dependant, which may (Or not) include editing 
> > Windows registry. Here are instructions that claim to work for Intel 
> > Southbridges, which since we're using ICH9, may possibily work for 
> > Xen based WXP VMs:
> > http://www.prime-expert.com/articles/a11/change-from-ide-to-ahci-without-reinstalling-windows-xp.php 
> >
> > But should these not work, chances are that you will need to add a 
> > rescue ISO to your DomU config file to repair the broken install, 
> > since I'm not 100% sure if you can even get it to boot in Safe Mode 
> > if it BSODs at boot.
> >
> > I think that's all what I could figure out. If you're using the GPLPV 
> > Drivers I don't know if there are any changes regarding running in 
> > AHCI mode.
> >
> >
> > ----------------------------------------
> > > Date: Mon, 8 Jun 2015 16:17:39 +0200
> > > From: fabio.fantoni@xxxxxxx
> > > To: stefano.stabellini@xxxxxxxxxxxxx
> > > CC: xen-devel@xxxxxxxxxxxxxxxxxxx; wei.liu2@xxxxxxxxxx; 
> > > Ian.Campbell@xxxxxxxxxx; Ian.Jackson@xxxxxxxxxxxxx; 
> > > Paul.Durrant@xxxxxxxxxx; anthony.perard@xxxxxxxxxx
> > > Subject: Re: [Xen-devel] [PATCH v2][RFC] libxl: Add AHCI support for 
> > > upstream qemu
> > > Il 08/06/2015 16:00, Stefano Stabellini ha scritto:
> > > > On Tue, 19 May 2015, Fabio Fantoni wrote:
> > > > > Il 19/05/2015 12:40, Wei Liu ha scritto:
> > > > > > On Mon, May 18, 2015 at 07:22:01PM +0200, Fabio Fantoni wrote:
> > > > > > > Il 18/05/2015 17:53, Wei Liu ha scritto:
> > > > > > > > On Thu, May 14, 2015 at 01:11:13PM +0200, Fabio Fantoni wrote:
> > > > > > > > > Usage:
> > > > > > > > > ahci=0|1 (default=0)
> > > > > > > > >
> > > > > > > > > If enabled adds ich9 disk controller in ahci mode and uses it 
> > > > > > > > > with
> > > > > > > > > upstream qemu to emulate disks instead of ide.
> > > > > > > > Is ICH9 available in our default setup?
> > > > > > > >
> > > > > > > > Why do we not always enable AHCI?
> > > > > > > ahci seems require ich9 controller (default in q35 but not in 
> > > > > > > older used
> > > > > > > by
> > > > > > > xen), I think that change it ide->ahci automatically for all 
> > > > > > > cases may
> > > > > > > causes problems, probably in save/restore and more probably in 
> > > > > > > windows <=7
> > > > > > > without pv where change ide<->ahci require a registry change for 
> > > > > > > not have
> > > > > > > blue screen.
> > > > > > I guess we now have a QEMU with Q35. But migrating from previous
> > > > > > previous versions will indeed need to be taken care of.
> > > > > This patch don't add q35 cipset support but only ich9 ahci disk 
> > > > > controller in
> > > > > older and only cipset supported in xen.
> > > > This is pretty nice actually, thanks for the patch!
> > > >
> > > >
> > > > > Time ago I tried to add q35 support in xen but I had some problems 
> > > > > I was
> > > > > unable to solves and nobody helped me.
> > > > > Q35 have newer ich9 ahci disk controller as default, on older 
> > > > > cipset must be
> > > > > added (done in this patch).
> > > > > qemu, kvm ovmf already support q35, xen need changes at least in 
> > > > > hvmloader
> > > > > (that I'm probably unable to do) and libxl (that I started time 
> > > > > ago without
> > > > > good result), Add ahci support and switch all qemu parameters in 
> > > > > libxl to new
> > > > > -device is a good start also for future q35 support (are both part 
> > > > > needed
> > > > > based on my old q35 tests on xen)
> > > > Yeah, going q35 opens a whole new can of worms. I think that adding 
> > > > the
> > > > ich9 chipset to the existing machine is a good compromise.
> > > >
> > > >
> > > > > > > > > It doesn't support cdroms which still use ide (cdroms will use
> > > > > > > > > "-device
> > > > > > > > > ide-cd" as new qemu parameters)
> > > > > > > > > Ahci requires new qemu parameters but for now other emulated 
> > > > > > > > > disks
> > > > > > > > > cases
> > > > > > > > > remains with old ones because automatic bus selection seems 
> > > > > > > > > bugged in
> > > > > > > > > qemu using new parameters. (I'll retry)
> > > > > > > > Buggy as in? Have you reported to QEMU upstream?
> > > > > > > Already reported long time ago in xen-devel and qemu-devel, the 
> > > > > > > only reply
> > > > > > > from qemu-devel was to use fixed bus and is what I did in v2 of 
> > > > > > > this
> > > > > > > patch.
> > > > > > > Can someone tell me if can be a problem fixed bus?
> > > > > > I don't have enough knowledge on this. Maybe Anthony and Stefano 
> > > > > > have
> > > > > > more insight.
> > > > Let me get this straight: cdrom still works but goes via ide. In
> > > > addition AHCI disks can be attached. Seems good to me.
> > > >
> > > > Have you tested Windows?
> > > >
> > > > If this works with Windows too, I would expose an ahci option
> > > > (default=off) in the config file. If ahci=on, then all disks could be
> > > > exposed via ahci. Does this seem sensible? In a couple of releases, if
> > > > it works well, we could make ahci=on the default.
> > > I tested both linux and windows, mainly windows domUs (7 and 8.1).
> > > Windows < 8 FWIK needs a registry key change for switch ide<->ahci
> > > without bluescreen (this is the reason because I did ahci=0|1 instead
> > > change it by default) but trying with windows 7 with pv is possible
> > > change without bluescreen, probably the problem is only without pv but
> > > ahci option default disabled resolve it (for the users don't set ahci=0
> > > on xen upgrade process).
> > > Based on what I know and all tests I did this patch seems the best way
> > > for add ahci support but I think that a experts (like you) review is 
> > > better.
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxx
> > > http://lists.xen.org/xen-devel

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