Re: [PATCH] x86/pvh: do not forward MADT Local APIC NMI structures to dom0

[Jan Beulich <jbeulich@suse.com>]

On 17.11.2022 11:23, Roger Pau Monné wrote:
> On Thu, Nov 17, 2022 at 10:27:41AM +0100, Jan Beulich wrote:
>> On 16.11.2022 17:42, Roger Pau Monne wrote:
>>> Currently Xen will passthrough any Local APIC NMI Structure found in
>>> the native ACPI MADT table to a PVH dom0.  This is wrong because PVH
>>> doesn't have access to the physical local APIC, and instead gets an
>>> emulated local APIC by Xen, that doesn't have the LINT0 or LINT1
>>> pins wired to anything.  Furthermore the ACPI Processor UIDs used in
>>> the APIC NMI Structures are likely to not match the ones generated by
>>> Xen for the Local x2APIC Structures, creating confusion to dom0.
>>
>> Plus we should have passed through Local x2APIC NMI Structures then as
>> well.
> 
> Sadly this is not possible for PVH dom0, Linux will use the ACPI
> Processor UID as vCPU ID in hypercalls, so if the UIDs don't start at
> 0 and are sequential Linux will panic during boot because vCPU
> operations will fail.

Sure - I was merely hinting at the original attempt having been incomplete
(besides being flawed as per the description here).

Jan