linux/virt, branch v6.0

KVM: Drop unnecessary initialization of "ops" in kvm_ioctl_create_device()

2022-08-19T08:05:43Z

The variable is initialized but it is only used after its assignment. Reviewed-by: Sean Christopherson Signed-off-by: Li kunyu Message-Id: <20220819021535.483702-1-kunyu@nfschina.com> Signed-off-by: Paolo Bonzini

KVM: Drop unnecessary initialization of "npages" in hva_to_pfn_slow()

2022-08-19T08:05:43Z

The variable is initialized but it is only used after its assignment. Reviewed-by: Sean Christopherson Signed-off-by: Li kunyu Message-Id: <20220819022804.483914-1-kunyu@nfschina.com> Signed-off-by: Paolo Bonzini

KVM: Rename mmu_notifier_* to mmu_invalidate_*

2022-08-19T08:05:41Z

The motivation of this renaming is to make these variables and related helper functions less mmu_notifier bound and can also be used for non mmu_notifier based page invalidation. mmu_invalidate_* was chosen to better describe the purpose of 'invalidating' a page that those variables are used for. - mmu_notifier_seq/range_start/range_end are renamed to mmu_invalidate_seq/range_start/range_end. - mmu_notifier_retry{_hva} helper functions are renamed to mmu_invalidate_retry{_hva}. - mmu_notifier_count is renamed to mmu_invalidate_in_progress to avoid confusion with mn_active_invalidate_count. - While here, also update kvm_inc/dec_notifier_count() to kvm_mmu_invalidate_begin/end() to match the change for mmu_notifier_count. No functional change intended. Signed-off-by: Chao Peng Message-Id: <20220816125322.1110439-3-chao.p.peng@linux.intel.com> Signed-off-by: Paolo Bonzini

KVM: Move coalesced MMIO initialization (back) into kvm_create_vm()

2022-08-19T08:02:31Z

Invoke kvm_coalesced_mmio_init() from kvm_create_vm() now that allocating and initializing coalesced MMIO objects is separate from registering any associated devices. Moving coalesced MMIO cleans up the last oddity where KVM does VM creation/initialization after kvm_create_vm(), and more importantly after kvm_arch_post_init_vm() is called and the VM is added to the global vm_list, i.e. after the VM is fully created as far as KVM is concerned. Originally, kvm_coalesced_mmio_init() was called by kvm_create_vm(), but the original implementation was completely devoid of error handling. Commit 6ce5a090a9a0 ("KVM: coalesced_mmio: fix kvm_coalesced_mmio_init()'s error handling" fixed the various bugs, and in doing so rightly moved the call to after kvm_create_vm() because kvm_coalesced_mmio_init() also registered the coalesced MMIO device. Commit 2b3c246a682c ("KVM: Make coalesced mmio use a device per zone") cleaned up that mess by having each zone register a separate device, i.e. moved device registration to its logical home in kvm_vm_ioctl_register_coalesced_mmio(). As a result, kvm_coalesced_mmio_init() is now a "pure" initialization helper and can be safely called from kvm_create_vm(). Opportunstically drop the #ifdef, KVM provides stubs for kvm_coalesced_mmio_{init,free}() when CONFIG_KVM_MMIO=n (s390). Signed-off-by: Sean Christopherson Message-Id: <20220816053937.2477106-4-seanjc@google.com> Signed-off-by: Paolo Bonzini

KVM: Unconditionally get a ref to /dev/kvm module when creating a VM

2022-08-19T08:02:31Z

Unconditionally get a reference to the /dev/kvm module when creating a VM instead of using try_get_module(), which will fail if the module is in the process of being forcefully unloaded. The error handling when try_get_module() fails doesn't properly unwind all that has been done, e.g. doesn't call kvm_arch_pre_destroy_vm() and doesn't remove the VM from the global list. Not removing VMs from the global list tends to be fatal, e.g. leads to use-after-free explosions. The obvious alternative would be to add proper unwinding, but the justification for using try_get_module(), "rmmod --wait", is completely bogus as support for "rmmod --wait", i.e. delete_module() without O_NONBLOCK, was removed by commit 3f2b9c9cdf38 ("module: remove rmmod --wait option.") nearly a decade ago. It's still possible for try_get_module() to fail due to the module dying (more like being killed), as the module will be tagged MODULE_STATE_GOING by "rmmod --force", i.e. delete_module(..., O_TRUNC), but playing nice with forced unloading is an exercise in futility and gives a falsea sense of security. Using try_get_module() only prevents acquiring _new_ references, it doesn't magically put the references held by other VMs, and forced unloading doesn't wait, i.e. "rmmod --force" on KVM is all but guaranteed to cause spectacular fireworks; the window where KVM will fail try_get_module() is tiny compared to the window where KVM is building and running the VM with an elevated module refcount. Addressing KVM's inability to play nice with "rmmod --force" is firmly out-of-scope. Forcefully unloading any module taints kernel (for obvious reasons) _and_ requires the kernel to be built with CONFIG_MODULE_FORCE_UNLOAD=y, which is off by default and comes with the amusing disclaimer that it's "mainly for kernel developers and desperate users". In other words, KVM is free to scoff at bug reports due to using "rmmod --force" while VMs may be running. Fixes: 5f6de5cbebee ("KVM: Prevent module exit until all VMs are freed") Cc: stable@vger.kernel.org Cc: David Matlack Signed-off-by: Sean Christopherson Message-Id: <20220816053937.2477106-3-seanjc@google.com> Signed-off-by: Paolo Bonzini

KVM: Properly unwind VM creation if creating debugfs fails

2022-08-19T08:02:30Z

Properly unwind VM creation if kvm_create_vm_debugfs() fails. A recent change to invoke kvm_create_vm_debug() in kvm_create_vm() was led astray by buggy try_get_module() handling adding by commit 5f6de5cbebee ("KVM: Prevent module exit until all VMs are freed"). The debugfs error path effectively inherits the bad error path of try_module_get(), e.g. KVM leaves the to-be-free VM on vm_list even though KVM appears to do the right thing by calling module_put() and falling through. Opportunistically hoist kvm_create_vm_debugfs() above the call to kvm_arch_post_init_vm() so that the "post-init" arch hook is actually invoked after the VM is initialized (ignoring kvm_coalesced_mmio_init() for the moment). x86 is the only non-nop implementation of the post-init hook, and it doesn't allocate/initialize any objects that are reachable via debugfs code (spawns a kthread worker for the NX huge page mitigation). Leave the buggy try_get_module() alone for now, it will be fixed in a separate commit. Fixes: b74ed7a68ec1 ("KVM: Actually create debugfs in kvm_create_vm()") Reported-by: syzbot+744e173caec2e1627ee0@syzkaller.appspotmail.com Cc: Oliver Upton Signed-off-by: Sean Christopherson Reviewed-by: Oliver Upton Message-Id: <20220816053937.2477106-2-seanjc@google.com> Signed-off-by: Paolo Bonzini

KVM: Actually create debugfs in kvm_create_vm()

2022-08-10T19:08:28Z

Doing debugfs creation after vm creation leaves things in a quasi-initialized state for a while. This is further complicated by the fact that we tear down debugfs from kvm_destroy_vm(). Align debugfs and stats init/destroy with the vm init/destroy pattern to avoid any headaches. Note the fix for a benign mistake in error handling for calls to kvm_arch_create_vm_debugfs() rolled in. Since all implementations of the function return 0 unconditionally it isn't actually a bug at the moment. Lastly, tear down debugfs/stats data in the kvm_create_vm_debugfs() error path. Previously it was safe to assume that kvm_destroy_vm() would take out the garbage, that is no longer the case. Signed-off-by: Oliver Upton Message-Id: <20220720092259.3491733-6-oliver.upton@linux.dev> Signed-off-by: Paolo Bonzini

KVM: Pass the name of the VM fd to kvm_create_vm_debugfs()

2022-08-10T19:08:28Z

At the time the VM fd is used in kvm_create_vm_debugfs(), the fd has been allocated but not yet installed. It is only really useful as an identifier in strings for the VM (such as debugfs). Treat it exactly as such by passing the string name of the fd to kvm_create_vm_debugfs(), futureproofing against possible misuse of the VM fd. Suggested-by: Sean Christopherson Signed-off-by: Oliver Upton Message-Id: <20220720092259.3491733-5-oliver.upton@linux.dev> Signed-off-by: Paolo Bonzini

KVM: Get an fd before creating the VM

2022-08-10T19:08:27Z

Allocate a VM's fd at the very beginning of kvm_dev_ioctl_create_vm() so that KVM can use the fd value to generate strigns, e.g. for debugfs, when creating and initializing the VM. Signed-off-by: Oliver Upton Message-Id: <20220720092259.3491733-4-oliver.upton@linux.dev> Signed-off-by: Paolo Bonzini

KVM: Shove vcpu stats_id init into kvm_vcpu_init()

2022-08-10T19:08:27Z

Initialize stats_id alongside other kvm_vcpu fields to make it more difficult to unintentionally access stats_id before it's set. No functional change intended. Signed-off-by: Oliver Upton Message-Id: <20220720092259.3491733-3-oliver.upton@linux.dev> Signed-off-by: Paolo Bonzini