> -----Original Message-----
> From: Ian Jackson <ian.jack...@citrix.com>
> Sent: 15 June 2020 17:38
> To: Roger Pau Monne <roger....@citrix.com>
> Cc: Grzegorz Uriasz <gorba...@gmail.com>; Jan Beulich <jbeul...@suse.com>;
> Andrew Cooper
> <andrew.coop...@citrix.com>; Kevin Tian <kevin.t...@intel.com>; Paul Durrant
> <p...@xen.org>; Wei Liu
> <w...@xen.org>; ja...@bartmin.ski; marma...@invisiblethingslab.com;
> j.nowa...@student.uw.edu.pl; Anthony
> Perard <anthony.per...@citrix.com>; xen-devel@lists.xenproject.org;
> cont...@puzio.waw.pl
> Subject: Re: [PATCH] libxl: tooling expects wrong errno
>
> Roger Pau Monne writes ("Re: [PATCH] libxl: tooling expects wrong errno"):
> > On Mon, Jun 15, 2020 at 03:59:50PM +0100, Ian Jackson wrote:
> > > Grzegorz Uriasz writes ("[PATCH] libxl: tooling expects wrong errno"):
> > > > When iommu is not enabled for a given domain then pci passthrough
> > > > hypercalls such as xc_test_assign_device return EOPNOTSUPP.
> > > > The code responsible for this is in "iommu_do_domctl" inside
> > > > xen/drivers/passthrough/iommu.c
> > > > This patch fixes the error message reported by libxl when assigning
> > > > pci devices to domains without iommu.
> > > >
> > > > Signed-off-by: Grzegorz Uriasz <gorba...@gmail.com>
> > > > Tested-by: Grzegorz Uriasz <gorba...@gmail.com>
> > > > ---
> > > > tools/libxl/libxl_pci.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
> > > > index 957ff5c8e9..bc5843b137 100644
> > > > --- a/tools/libxl/libxl_pci.c
> > > > +++ b/tools/libxl/libxl_pci.c
> > > > @@ -1561,7 +1561,7 @@ void libxl__device_pci_add(libxl__egc *egc,
> > > > uint32_t domid,
> > > > LOGD(ERROR, domid,
> > > > "PCI device %04x:%02x:%02x.%u %s?",
> > > > pcidev->domain, pcidev->bus, pcidev->dev,
> > > > pcidev->func,
> > > > - errno == ENOSYS ? "cannot be assigned - no IOMMU"
> > > > + errno == EOPNOTSUPP ? "cannot be assigned - no IOMMU"
> > > > : "already assigned to a different guest");
> > > > goto out;
> > > > }
> > >
> > > Thanks. I have addressed some Xen IOMMU maintainers. Can you confirm
> > > whether this is right ?
> >
> > Not an IOMMU maintainer myself, but I've taken a look at the code and
> > I think Grzegorz is right. iommu_do_domctl will return -EOPNOTSUPP if
> > the IOMMU is not enabled for the domain. Another option would be to
> > check for EBUSY (which will certainly be returned when the device is
> > busy) and log the error code with a message when it's different than
> > EBUSY?
> >
> > There are many possible error here, for example the device itself
> > might not be behind an IOMMU, in which case Xen will return -ENODEV at
> > least on the Intel case.
>
> Thanks for the analysis. So:
>
> Acked-by: Ian Jackson <ian.jack...@eu.citrix.com>
>
> This would seem to be a backport candidate. AFAICT check has been
> there, looking for ENOSYS, since this code was introduced in
> 826eb17271d3c647516d9944c47b0779afedea25
> libxl: suppress device assignment to HVM guest when there is no IOMMU
> ?
>
> But that commit has a Tested-by. Maybe Xen changed its error return
> at some point ?
>
Yes, it happened in 71e617a6b8f69849c70eda1b3c58f1ff6b244e5a
use is_iommu_enabled() where appropriate...
Paul
> Ian.
