linux-kernel - [PATCH v2 0/8] KVM: SVM: Fix exit

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Message-ID: <20251230211347.4099600-1-seanjc@google.com>
Date: Tue, 30 Dec 2025 13:13:39 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, 
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, 
	Dexuan Cui <decui@...rosoft.com>, Long Li <longli@...rosoft.com>
Cc: kvm@...r.kernel.org, linux-hyperv@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH v2 0/8] KVM: SVM: Fix exit_code bugs

Fix (mostly benign) bugs in SVM where KVM treats exit codes as 32-bit values
instead of 64-bit values.

The most dangerous aspect of the mess is that simply fixing KVM would likely
break KVM-on-KVM setups if only L1 is patched.  To try and avoid such
breakage while also fixing KVM, I opted to have KVM retain its checks on
only bits 31:0 if KVM is running as a VM (as detected by
X86_FEATURE_HYPERVISOR).

v2: 
 - Drop the nSVM #VMEXIT fixes (already merged).
 - Collect reviews. [Yosry]
 - Fix inverted svm_is_vmrun_failure() check. [Yosry]
 - Use __print_symbolic_u64() and __print_flags_u64() in tracepoints. [Test Bot]
 - Track exit_code as a u64 in KVM selftests.
 - Make HV_SVM_EXITCODE_ENL an ull like everything else. [Michael]
 - Add a compile-time assertion to verify HV_SVM_EXITCODE_ENL == SVM_EXIT_SW.

v1: https://lore.kernel.org/all/20251113225621.1688428-1-seanjc@google.com


Sean Christopherson (8):
  KVM: SVM: Add a helper to detect VMRUN failures
  KVM: SVM: Open code handling of unexpected exits in
    svm_invoke_exit_handler()
  KVM: SVM: Check for an unexpected VM-Exit after RETPOLINE "fast"
    handling
  KVM: SVM: Filter out 64-bit exit codes when invoking exit handlers on
    bare metal
  KVM: SVM: Treat exit_code as an unsigned 64-bit value through all of
    KVM
  KVM: SVM: Limit incorrect check on SVM_EXIT_ERR to running as a VM
  KVM: SVM: Harden exit_code against being used in Spectre-like attacks
  KVM: SVM: Assert that Hyper-V's HV_SVM_EXITCODE_ENL == SVM_EXIT_SW

 arch/x86/include/asm/svm.h                    |  3 +-
 arch/x86/include/uapi/asm/svm.h               | 32 ++++++------
 arch/x86/kvm/svm/hyperv.c                     |  7 ++-
 arch/x86/kvm/svm/nested.c                     | 29 ++++-------
 arch/x86/kvm/svm/sev.c                        | 36 +++++--------
 arch/x86/kvm/svm/svm.c                        | 51 +++++++++++--------
 arch/x86/kvm/svm/svm.h                        | 12 +++--
 arch/x86/kvm/trace.h                          |  6 +--
 include/hyperv/hvgdk.h                        |  2 +-
 tools/testing/selftests/kvm/include/x86/svm.h |  3 +-
 .../kvm/x86/svm_nested_soft_inject_test.c     |  4 +-
 11 files changed, 90 insertions(+), 95 deletions(-)


base-commit: 9448598b22c50c8a5bb77a9103e2d49f134c9578
-- 
2.52.0.351.gbe84eed79e-goog