Commits
Jan Dakinevich authored and Konstantin Khorenko committed 6bee5035ac2
ms/KVM: x86: always stop emulation on page fault inject_emulated_exception() returns true if and only if nested page fault happens. However, page fault can come from guest page tables walk, either nested or not nested. In both cases we should stop an attempt to read under RIP and give guest to step over its own page fault handler. This is also visible when an emulated instruction causes a #GP fault and the VMware backdoor is enabled. To handle the VMware backdoor, KVM intercepts #GP faults; with only the next patch applied, x86_emulate_instruction() injects a #GP but returns EMULATE_FAIL instead of EMULATE_DONE. EMULATE_FAIL causes handle_exception_nmi() (or gp_interception() for SVM) to re-inject the original #GP because it thinks emulation failed due to a non-VMware opcode. This patch prevents the issue as x86_emulate_instruction() will return EMULATE_DONE after injecting the #GP. Fixes: 6ea6e84309ca ("KVM: x86: inject exceptions produced by x86_decode_insn") Cc: stable@vger.kernel.org Cc: Denis Lunev <den@virtuozzo.com> Cc: Roman Kagan <rkagan@virtuozzo.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Signed-off-by: Jan Dakinevich <jan.dakinevich@virtuozzo.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> https://jira.sw.ru/browse/PSBM-68018 (cherry-picked from 8530a79c5a9f4e29e6ffb35ec1a79d81f4968ec8) ===================== Patchset description: fix emulation error on Windows bootup This series intended to fix (again) a bug that was a subject of the following change: 6ea6e84 ("KVM: x86: inject exceptions produced by x86_decode_insn") Suddenly, that fix had a couple mistakes. First, ctxt->have_exception was not set if fault happened during instruction decoding. Second, returning value of inject_emulated_instruction was used to make the decision to reenter guest, but this could happen iff on nested page fault, that is not the scope where this bug could occur. https://lkml.org/lkml/2019/8/29/152 Jan Dakinevich (2): KVM: x86: always stop emulation on page fault KVM: x86: set ctxt->have_exception in x86_decode_insn() Paolo Bonzini (1): KVM: x86: inject exceptions produced by x86_decode_insn