linux-kernel - [PATCH 0/2] KVM: x86: Do runtime updates during KVM_SET

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Message-ID: <20251202015049.1167490-1-seanjc@google.com>
Date: Mon,  1 Dec 2025 17:50:47 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Igor Mammedov <imammedo@...hat.com>
Subject: [PATCH 0/2] KVM: x86: Do runtime updates during KVM_SET_CPUID2

Do runtime updates (if necessary) when userspace sets CPUID to fix a bug
where KVM drops a pending update (KVM will clear the dirty flag when doing
updates on the new/incoming CPUID).  The bug most visibly manifests as an
-EINVAL failure on KVM_SET_CPUID{,2} due to the old/current CPUID not
matching the new/incoming CPUID, but if userspace were to continue running
past the failure, the vCPU would run with stale CPUID/caps.

Sean Christopherson (2):
  KVM: x86: Apply runtime updates to current CPUID during
    KVM_SET_CPUID{,2}
  KVM: selftests: Add a CPUID testcase for KVM_SET_CPUID2 with runtime
    updates

 arch/x86/kvm/cpuid.c                         | 11 +++++++++--
 tools/testing/selftests/kvm/x86/cpuid_test.c | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)


base-commit: 115d5de2eef32ac5cd488404b44b38789362dbe6
-- 
2.52.0.107.ga0afd4fd5b-goog