Re: [Xen-devel] [PATCH v4] libxl: Add AHCI support for upstream qemu

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2015-07-09 at 12:36 +0200, Fabio Fantoni wrote:
> Il 09/07/2015 12:26, Ian Campbell ha scritto:
> > On Wed, 2015-07-08 at 16:31 +0200, Fabio Fantoni wrote:
> >> Usage:
> >> hdtype=ide|ahci (default=ide)
> >>
> >> If hdtype=ahci adds ich9 disk controller in ahci mode and uses it with
> >> upstream qemu to emulate disks instead of ide.
> >> It doesn't support cdroms which still using ide (cdroms will use
> >> "-device ide-cd" as new qemu parameter)
> >> Ahci requires new qemu parameter but for now other emulated disks cases
> >> remains with old ones (I did it in other patch, not needed by this one)
> >> I did it as libxl parameter disabled by default to avoid possible
> >> problems:
> >> - with save/restore/migration (restoring with ahci a domU that was with
> >> ide instead)
> >> - windows < 8 without pv drivers (a registry key change is needed for
> >> AHCI<->IDE change FWIK to avoid possible blue screen)
> >> - windows XP or older that many not support ahci by default.
> >> Setting AHCI with libxl parameter and default to disabled seems the best
> >> solution.
> >> AHCI increase hvm domUs boot performance. On linux hvm domU I saw up to
> >> only 20% of the previous total boot time, whereas boot time decrease a
> >> lot on W7 domUs for most of boots I have done. Small difference in boot
> >> time compared to ide mode on W8 and newer (probably other xen
> >> improvements or fixes are needed not ahci related)
> >>
> >> Signed-off-by: Fabio Fantoni <fabio.fantoni@xxxxxxx>
> >>
> >> ---
> >>
> >> Changes in v4:
> >> - libxl.h: LIBXL_HAVE_AHCI->LIBXL_HAVE_HVM_AHCI
> > In retrospect this should have been LIBXL_HAVE_HVM_HDTYPE. Since the
> > above was my suggestion if you agree I can make that simple change as I
> > commit.
> 
> Yes you can change it directly as this change not risk introduce bug, 
> thanks.

Thanks I'll do this.

> Is also Stabellini Acked-by (he did in v2) needed for qemu parameters 
> part (not changed in v3 and v4)?
> http://lists.xen.org/archives/html/xen-devel/2015-06/msg03551.html
> I not added in latest posted version because I don't know if can be 
> still valid.

Right. I had been planning to take that ack on v2 into consideration (as
validating the set of qemu parameters used) but in the absence of him
having specified that constraint explicitly or having acked the latest
version I wasn't going to add his Ack and I think you did the right
thing by dropping it.

I'll apply shortly.

Ian.


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