On Fri, 2022-03-11 at 03:27 +0000, Sean Christopherson wrote: > 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 I am just curious. Are you aware that I worked on this few months ago? I am sure that you even reviewed some of my code back then. If so, could you have had at least mentioned this and/or pinged me to continue working on this instead of re-implementing it? Best regards, Maxim Levitsky
