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Re: [PATCH] x86/IOMMU: mark IOMMU / intremap not in use when ACPI tables are missing
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 21 Oct 2021 09:37:23 +0200
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- Cc: Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 21 Oct 2021 07:37:39 +0000
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On 21.10.2021 09:21, Jan Beulich wrote:
> On 20.10.2021 22:01, Andrew Cooper wrote:
>> However, I don't think skipping parsing is a sensible move. Intremap is
>> utterly mandatory if during boot, we discover that our APIC ID is >254,
>> and iommu=no-intremap must be ignored in this case, or if the MADT says
>> we have CPUs beyond that limit and the user hasn't specified nr_cpus=1
>> or equivalent.
>
> Reading this made me realize that the change breaks other behavior.
> The conditional really needs to be iommu_enable || iommu_intremap -
> at least AMD code added in support for x2APIC already treats the
> latter to not be a sub-option of the former (iov_supports_xt(),
> acpi_ivrs_init()), and e.g. intel_iommu_supports_eim() also checks
> the latter alone.
Actually the check in iov_supports_xt() is wrong - it needs to use
&&, not ||. I'll make a 2nd patch ...
Jan
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