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Reply-To: Sean Christopherson <seanjc@google.com>
Date:   Fri, 11 Mar 2022 03:27:40 +0000
Message-Id: <20220311032801.3467418-1-seanjc@google.com>
Mime-Version: 1.0
Subject: [PATCH 00/21] KVM: x86: Event/exception fixes and cleanups
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Oliver Upton <oupton@google.com>,
        Peter Shier <pshier@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

The main goal of this series is to fix KVM's longstanding bug of not
honoring L1's exception intercepts wants when handling an exception that
occurs during delivery of a different exception.  E.g. if L0 and L1 are
using shadow paging, and L2 hits a #PF, and then hits another #PF while
vectoring the first #PF due to _L1_ not having a shadow page for the IDT,
KVM needs to check L1's intercepts before morphing the #PF => #PF => #DF
so that the #PF is routed to L1, not injected into L2 as a #DF.

nVMX has hacked around the bug for years by overriding the #PF injector
for shadow paging to go straight to VM-Exit, and nSVM has started doing
the same.  The hacks mostly work, but they're incomplete, confusing, and
lead to other hacky code, e.g. bailing from the emulator because #PF
injection forced a VM-Exit and suddenly KVM is back in L1.

Everything leading up to that are related fixes and cleanups I encountered
along the way; some through code inspection, some through tests (I truly
thought this series was finished 10 commits and 3 days ago...).

Nothing in here is all that urgent; all bugs tagged for stable have been
around for multiple releases (years in most cases).

Sean Christopherson (21):
  KVM: x86: Return immediately from x86_emulate_instruction() on code
    #DB
  KVM: nVMX: Unconditionally purge queued/injected events on nested
    "exit"
  KVM: VMX: Drop bits 31:16 when shoving exception error code into VMCS
  KVM: x86: Don't check for code breakpoints when emulating on exception
  KVM: nVMX: Treat General Detect #DB (DR7.GD=1) as fault-like
  KVM: nVMX: Prioritize TSS T-flag #DBs over Monitor Trap Flag
  KVM: x86: Treat #DBs from the emulator as fault-like (code and
    DR7.GD=1)
  KVM: x86: Use DR7_GD macro instead of open coding check in emulator
  KVM: nVMX: Ignore SIPI that arrives in L2 when vCPU is not in WFS
  KVM: nVMX: Unconditionally clear mtf_pending on nested VM-Exit
  KVM: VMX: Inject #PF on ENCLS as "emulated" #PF
  KVM: x86: Rename kvm_x86_ops.queue_exception to inject_exception
  KVM: x86: Make kvm_queued_exception a properly named, visible struct
  KVM: x86: Formalize blocking of nested pending exceptions
  KVM: x86: Use kvm_queue_exception_e() to queue #DF
  KVM: x86: Hoist nested event checks above event injection logic
  KVM: x86: Evaluate ability to inject SMI/NMI/IRQ after potential
    VM-Exit
  KVM: x86: Morph pending exceptions to pending VM-Exits at queue time
  KVM: VMX: Update MTF and ICEBP comments to document KVM's subtle
    behavior
  KVM: selftests: Use uapi header to get VMX and SVM exit reasons/codes
  KVM: selftests: Add an x86-only test to verify nested exception
    queueing

 arch/x86/include/asm/kvm-x86-ops.h            |   2 +-
 arch/x86/include/asm/kvm_host.h               |  33 +-
 arch/x86/kvm/emulate.c                        |   3 +-
 arch/x86/kvm/svm/nested.c                     | 100 ++---
 arch/x86/kvm/svm/svm.c                        |  18 +-
 arch/x86/kvm/vmx/nested.c                     | 322 +++++++++-----
 arch/x86/kvm/vmx/sgx.c                        |   2 +-
 arch/x86/kvm/vmx/vmx.c                        |  53 ++-
 arch/x86/kvm/x86.c                            | 409 ++++++++++++------
 arch/x86/kvm/x86.h                            |  10 +-
 tools/testing/selftests/kvm/.gitignore        |   1 +
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../selftests/kvm/include/x86_64/svm_util.h   |   5 +-
 .../selftests/kvm/include/x86_64/vmx.h        |  51 +--
 .../kvm/x86_64/nested_exceptions_test.c       | 307 +++++++++++++
 15 files changed, 914 insertions(+), 403 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86_64/nested_exceptions_test.c


base-commit: 4a204f7895878363ca8211f50ec610408c8c70aa
-- 
2.35.1.723.g4982287a31-goog