Re: [Xen-devel] [PATCH v2 1/2] AMD/IOMMU: correct handling when XT's prereq features are unavailable

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

On Fri, Feb 28, 2020 at 01:10:59PM +0100, Jan Beulich wrote:
> We should neither cause IOMMU initialization as a whole to fail in this
> case (we should still be able to bring up the system in non-x2APIC or
> x2APIC physical mode), nor should the remainder of the function be
> skipped (as the main part of it won't get entered a 2nd time)

I'm not sure I see why it won't get entered a second time. AFAICT
init_done won't be set if amd_iommu_init fails, and hence will be
called again with xt == false in iov_detect?

> in such an
> event. It is merely necessary for the function to indicate to the caller
> (iov_supports_xt()) that setup failed as far as x2APIC is concerned.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

LGTM, but it needs to go in with 2/2 AFAICT, or else you would report
interrupt remapping enabled and x2APIC also enabled but won't handle
correctly a 32 bit destination field.

Thanks, Roger.

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