mainlining shenanigans
8d25b7beca
kvm_arch_vcpu_ioctl_run is already doing srcu_read_lock/unlock in two places, namely vcpu_run and post_kvm_run_save, and a third is actually needed around the call to vcpu->arch.complete_userspace_io to avoid the following splat: WARNING: suspicious RCU usage arch/x86/kvm/pmu.c:190 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by CPU 28/KVM/370841: #0: ff11004089f280b8 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x87/0x730 [kvm] Call Trace: <TASK> dump_stack_lvl+0x59/0x73 reprogram_fixed_counter+0x15d/0x1a0 [kvm] kvm_pmu_trigger_event+0x1a3/0x260 [kvm] ? free_moved_vector+0x1b4/0x1e0 complete_fast_pio_in+0x8a/0xd0 [kvm] This splat is not at all unexpected, since complete_userspace_io callbacks can execute similar code to vmexits. For example, SVM with nrips=false will call into the emulator from svm_skip_emulated_instruction(). While it's tempting to never acquire kvm->srcu for an uninitialized vCPU, practically speaking there's no penalty to acquiring kvm->srcu "early" as the KVM_MP_STATE_UNINITIALIZED path is a one-time thing per vCPU. On the other hand, seemingly innocuous helpers like kvm_apic_accept_events() and sync_regs() can theoretically reach code that might access SRCU-protected data structures, e.g. sync_regs() can trigger forced existing of nested mode via kvm_vcpu_ioctl_x86_set_vcpu_events(). Reported-by: Like Xu <likexu@tencent.com> Co-developed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.