[v2,0/2] APICv-related fixes for inhibits and tracepoint

Message

Alejandro Jimenez April 18, 2024, 2:18 a.m. UTC

v2: Add Sean's changes to [PATCH 1/2].

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Patch 1 fixes an issue when avic=0 (current default) where
APICV_INHIBIT_REASON_ABSENT remains set even after an in-kernel local APIC has
been created. e.g. tracing the inhibition tracepoint shows:

<...>-196432  [247] ..... 70380.628931: kvm_apicv_inhibit_changed: set reason=2, inhibits=0x4
<...>-196432  [247] ..... 70380.628941: kvm_apicv_inhibit_changed: set reason=0, inhibits=0x5

and the reason=2 inhibit is not removed after the local APIC is created.

Patch 2 modifies the wording in the pi_irte_update tracepoint to make it clear
that it is used by the posted interrupt implementation of both vendors. I have
reservations about modifying the tracepoint output and breaking user scripts,
but according to recent discussions tracepoints are not strictly a stable ABI,
so I'd consider this minor change to avoid confusion around this area.

Thank you,
Alejandro


Alejandro Jimenez (2):
  KVM: x86: Only set APICV_INHIBIT_REASON_ABSENT if APICv is enabled
  KVM: x86: Remove VT-d mention in posted interrupt tracepoint

 arch/x86/kvm/trace.h |  4 ++--
 arch/x86/kvm/x86.c   | 13 ++++++-------
 2 files changed, 8 insertions(+), 9 deletions(-)


base-commit: 2d181d84af38146748042a6974c577fc46c3f1c3

Comments

Sean Christopherson May 3, 2024, 9:32 p.m. UTC | #1

On Thu, 18 Apr 2024 02:18:21 +0000, Alejandro Jimenez wrote:
> v2: Add Sean's changes to [PATCH 1/2].
> 
> --
> 
> Patch 1 fixes an issue when avic=0 (current default) where
> APICV_INHIBIT_REASON_ABSENT remains set even after an in-kernel local APIC has
> been created. e.g. tracing the inhibition tracepoint shows:
> 
> [...]

Applied to kvm-x86 misc, with the previously mentioned fixups, thanks!

[1/2] KVM: x86: Only set APICV_INHIBIT_REASON_ABSENT if APICv is enabled
      https://github.com/kvm-x86/linux/commit/6982b34c21cb
[2/2] KVM: x86: Remove VT-d mention in posted interrupt tracepoint
      https://github.com/kvm-x86/linux/commit/51937f2aae18

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https://github.com/kvm-x86/linux/tree/next