From: Cyril Novikov <cnovikov@lynx.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Philipp Eppelt <philipp.eppelt@kernkonzept.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: x86/apic: MSI address malformed for "flat" driver
Date: Mon, 10 Sep 2018 23:02:46 -0700 [thread overview]
Message-ID: <27bccfd2-0ede-cd3a-2717-741d3dffebdf@lynx.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1809072012310.1402@nanos.tec.linutronix.de>
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
next prev parent reply other threads:[~2018-09-11 6:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 9:22 x86/apic: MSI address malformed for "flat" driver Philipp Eppelt
2018-09-07 19:11 ` Thomas Gleixner
2018-09-11 6:02 ` Cyril Novikov [this message]
2018-09-11 12:29 ` Thomas Gleixner
2018-10-01 14:24 ` Philipp Eppelt
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