linux-kernel - [PATCH 00/10] KVM: Avoid literal numbers as return values

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Message-ID: <20251205074537.17072-1-jgross@suse.com>
Date: Fri,  5 Dec 2025 08:45:27 +0100
From: Juergen Gross <jgross@...e.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	x86@...nel.org,
	linux-coco@...ts.linux.dev
Cc: Juergen Gross <jgross@...e.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Kiryl Shutsemau <kas@...nel.org>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Paul Durrant <paul@....org>
Subject: [PATCH 00/10] KVM: Avoid literal numbers as return values

This series is the first part of replacing the use of literal numbers
(0 and 1) as return values with either true/false or with defines.

This work is a prelude of getting rid of the magic value "1" for
"return to guest". I started in x86 KVM host code doing that and soon
stumbled over lots of other use cases of the magic "1" as return value,
especially in MSR emulation where a comment even implied this "1" was
due to the "return to guest" semantics.

A detailed analysis of all related code paths revealed that there was
indeed a rather clean interface between the functions using the MSR
emulation "1" and those using the "return to guest" "1". 

A few functions just using "0" and "1" instead of bool are changed,
tooi (patches 1-4).

The rest of the series is cleaning up the MSR emulation code by using
new proper defines for return values 0 and 1.

The whole series should not result in any functional change.

Juergen Gross (10):
  KVM: Switch coalesced_mmio_in_range() to return bool
  KVM/x86: Use bool for the err parameter of kvm_complete_insn_gp()
  KVM/x86: Let x86_emulate_ops.set_cr() return a bool
  KVM/x86: Let x86_emulate_ops.set_dr() return a bool
  KVM/x86: Add KVM_MSR_RET_* defines for values 0 and 1
  KVM/x86: Use defines for APIC related MSR emulation
  KVM/x86: Use defines for Hyper-V related MSR emulation
  KVM/x86: Use defines for VMX related MSR emulation
  KVM/x86: Use defines for SVM related MSR emulation
  KVM/x86: Use defines for common related MSR emulation

 arch/x86/include/asm/kvm_host.h |  14 +-
 arch/x86/kvm/emulate.c          |   2 +-
 arch/x86/kvm/hyperv.c           | 110 +++++++-------
 arch/x86/kvm/kvm_emulate.h      |   4 +-
 arch/x86/kvm/lapic.c            |  48 +++----
 arch/x86/kvm/mtrr.c             |  12 +-
 arch/x86/kvm/pmu.c              |  12 +-
 arch/x86/kvm/smm.c              |   2 +-
 arch/x86/kvm/svm/pmu.c          |  12 +-
 arch/x86/kvm/svm/svm.c          |  54 +++----
 arch/x86/kvm/vmx/main.c         |   2 +-
 arch/x86/kvm/vmx/nested.c       |  18 +--
 arch/x86/kvm/vmx/pmu_intel.c    |  20 +--
 arch/x86/kvm/vmx/tdx.c          |  18 +--
 arch/x86/kvm/vmx/tdx.h          |   2 +-
 arch/x86/kvm/vmx/vmx.c          | 122 ++++++++--------
 arch/x86/kvm/x86.c              | 246 ++++++++++++++++----------------
 arch/x86/kvm/x86.h              |  10 +-
 arch/x86/kvm/xen.c              |  14 +-
 virt/kvm/coalesced_mmio.c       |  14 +-
 20 files changed, 372 insertions(+), 364 deletions(-)

-- 
2.51.0