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| author | Sean Christopherson <seanjc@google.com> | 2022-02-23 16:53:02 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-04-02 05:34:39 -0400 |
| commit | df06dae3f2a8bfb83683abf88d3dcde23fc8093d (patch) | |
| tree | b0ab56a8dc998cf99132ba5335b24c90d9dc7681 /Documentation/virt | |
| parent | 79593c086eb95eb2886f36ee6f78a1d6845e1bdf (diff) | |
| download | linux-df06dae3f2a8bfb83683abf88d3dcde23fc8093d.tar.gz | |
KVM: Don't actually set a request when evicting vCPUs for GFN cache invd
Don't actually set a request bit in vcpu->requests when making a request purely to force a vCPU to exit the guest. Logging a request but not actually consuming it would cause the vCPU to get stuck in an infinite loop during KVM_RUN because KVM would see the pending request and bail from VM-Enter to service the request. Note, it's currently impossible for KVM to set KVM_REQ_GPC_INVALIDATE as nothing in KVM is wired up to set guest_uses_pa=true. But, it'd be all too easy for arch code to introduce use of kvm_gfn_to_pfn_cache_init() without implementing handling of the request, especially since getting test coverage of MMU notifier interaction with specific KVM features usually requires a directed test. Opportunistically rename gfn_to_pfn_cache_invalidate_start()'s wake_vcpus to evict_vcpus. The purpose of the request is to get vCPUs out of guest mode, it's supposed to _avoid_ waking vCPUs that are blocking. Opportunistically rename KVM_REQ_GPC_INVALIDATE to be more specific as to what it wants to accomplish, and to genericize the name so that it can used for similar but unrelated scenarios, should they arise in the future. Add a comment and documentation to explain why the "no action" request exists. Add compile-time assertions to help detect improper usage. Use the inner assertless helper in the one s390 path that makes requests without a hardcoded request. Cc: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20220223165302.3205276-1-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/kvm/vcpu-requests.rst | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/vcpu-requests.rst b/Documentation/virt/kvm/vcpu-requests.rst index b61d48aec36c..db43ee571f5a 100644 --- a/Documentation/virt/kvm/vcpu-requests.rst +++ b/Documentation/virt/kvm/vcpu-requests.rst @@ -135,6 +135,16 @@ KVM_REQ_UNHALT such as a pending signal, which does not indicate the VCPU's halt emulation should stop, and therefore does not make the request. +KVM_REQ_OUTSIDE_GUEST_MODE + + This "request" ensures the target vCPU has exited guest mode prior to the + sender of the request continuing on. No action needs be taken by the target, + and so no request is actually logged for the target. This request is similar + to a "kick", but unlike a kick it guarantees the vCPU has actually exited + guest mode. A kick only guarantees the vCPU will exit at some point in the + future, e.g. a previous kick may have started the process, but there's no + guarantee the to-be-kicked vCPU has fully exited guest mode. + KVM_REQUEST_MASK ---------------- |