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Differential D55429

Xen: Detect Extended Destination ID support
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Authored by cperciva on Sun, Feb 22, 4:10 AM.
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imp

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royger
Summary

Xen advertises support for the Extended Destination ID standard via
bit 5 (aka XEN_HVM_CPUID_EXT_DEST_ID) of the value returned in the
EAX register when Xen features are queried via CPUID.

MFC after: 2 weeks

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rG FreeBSD src repository
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Buildable 70927
Build 67810: arc lint + arc unit

Event Timeline

cperciva created this revision.Sun, Feb 22, 4:10 AM
Herald added a subscriber: imp. · View Herald TranscriptSun, Feb 22, 4:10 AM
cperciva requested review of this revision.Sun, Feb 22, 4:10 AM
cperciva added a parent revision: D55428: x86/cpuid: add CPUID flag for Extended Destination ID support.
Harbormaster completed remote builds in B70868: Diff 172428.Sun, Feb 22, 4:11 AM
cperciva added a child revision: D55430: vmm: Move defines from x86.c to x86/bhyve.h.Sun, Feb 22, 4:11 AM
cperciva added a reviewer: royger.Sun, Feb 22, 4:14 AM
cperciva updated this revision to Diff 172539.Mon, Feb 23, 7:53 PM

Only enable if ext_dest_id is set to -1.

Harbormaster completed remote builds in B70927: Diff 172539.Mon, Feb 23, 7:53 PM
royger added a comment.Tue, Feb 24, 2:57 PM

I think I'm missing the previous changes that introduce the support for KVM, as those haven't landed in the git repository yet. FWIW, while the CPUID has been reserved on Xen, the implementation is not done, so there's no way to test it on Xen.

sys/x86/x86/msi.c
398

Why are you doing the detection in MSI init code? The usage of the extended destination ID is not limited to MSI, and can also be used with IO-APIC RTEs. It should likely be done in a more generic place, maybe at interrupt initialization? So that it can be used by the IO-APIC.

cperciva added a comment.Wed, Feb 25, 7:16 AM
In D55429#1269504, @royger wrote:

I think I'm missing the previous changes that introduce the support for KVM, as those haven't landed in the git repository yet. FWIW, while the CPUID has been reserved on Xen, the implementation is not done, so there's no way to test it on Xen.

The KVM detection is just before this in the stack: https://reviews.freebsd.org/D55427 . And the code which uses ext_dest_id is in https://reviews.freebsd.org/D55426.

cperciva added inline comments.Wed, Feb 25, 7:19 AM
sys/x86/x86/msi.c
398

I'm doing it here because this is the file where I needed to use it (see the earlier patch).

But you're right that I forgot about IO-APIC RTEs. I need to understand our code for those better...

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Diff 172539

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sys/x86/x86/msi.c

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