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SubjectRe: x86/apic: MSI address malformed for "flat" driver
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On 9/7/2018 12:11 PM, Thomas Gleixner wrote:
> On Thu, 6 Sep 2018, Philipp Eppelt wrote:
>>
>> The "flat" driver defines the MSI addressing scheme to be used as
>> logical addressing in flat mode. The MSI msg address is composed
>> accordingly, but sets MSI_ADDR_REDIRECTION_CPU which is a zero at bit[3].
>
> Correct. That's what it means:
>
> * When RH is 0, the interrupt is directed to the processor listed in the
> Destination ID field.
>
> So for DM:
>
> * If RH is 0, then the DM bit is ignored and the message is sent ahead
> independent of whether the physical or logical destination mode is
> used.
>
> which is means that the delivery does not do any magic redirections,
> because the Redirection Hint is off. If RH is set, then the delivery can
> redirect according to the rules in the DM section. We are not using that
> because we want targeted single CPU delivery.
>
> The interpretation of the DID field is purely depending on the local APIC
> itself by matching the APIC ID against the DID field. And the local APIC ID
> of CPU0 is 1 << 0, i.e. 0x1 which matches the MSI message you see.

I believe you are wrong here and the local APIC ID of CPU0 is 0.

processor : 0
vendor_id : GenuineIntel
...
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
apicid : 0

The fact that the code works means that DM is not ignored when RH is 0.
In other words, RH=0 DM=1 means logical destination mode.

--
Cyril

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