Re: [Xen-devel] [PATCH v3 7/7] xen/dom0: Add a dom0-iommu=none option

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Jan 16, 2019 at 09:00:50AM +0000, Andrew Cooper wrote:
> For development purposes, it is very convenient to boot Xen as a PVH guest,
> with an XTF PV or PVH "dom0".  The edit-compile-go cycle is a matter of
> seconds, and you can reasonably insert printk() debugging in places which
> which would be completely infeasible when booting fully-fledged guests.
> 
> However, the PVH dom0 path insists on having a working IOMMU, which doesn't
> exist when virtualised as a PVH guest, and isn't necessary for XTF anyway.
> 
> Introduce a developer mode to skip the IOMMU requirement.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> 
> v2:
>  * Retain `none` as opposed to repurposing `passthrough`.  It turns out
>    that they are different.
>  * Update cmdline_strcmp() to look only for commas.
> v3:
>  * Rebase over splitting cmdline_strcmp() out into a standalone fix.
> ---
>  docs/misc/xen-command-line.pandoc | 8 +++++++-
>  xen/drivers/passthrough/iommu.c   | 5 ++++-
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/misc/xen-command-line.pandoc 
> b/docs/misc/xen-command-line.pandoc
> index ccfad4c..410a7f6 100644
> --- a/docs/misc/xen-command-line.pandoc
> +++ b/docs/misc/xen-command-line.pandoc
> @@ -667,7 +667,7 @@ Controls for how dom0 is constructed on x86 systems.
>      information during the dom0 build.  It defaults to false.
>  
>  ### dom0-iommu
> -    = List of [ passthrough=<bool>, strict=<bool>, map-reserved=<bool> ]
> +    = List of [ passthrough=<bool>, strict=<bool>, map-reserved=<bool>, none 
> ]

I would also be fine with using dom0-iommu = [ <bool>, ... ] but
that's also fine and less confusing.

Thanks, Roger.

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