user/sven/linux.git/include/linux/kvm_host.h, branch v6.9.5

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2024-03-15T20:03:13Z

Pull kvm updates from Paolo Bonzini: "S390: - Changes to FPU handling came in via the main s390 pull request - Only deliver to the guest the SCLP events that userspace has requested - More virtual vs physical address fixes (only a cleanup since virtual and physical address spaces are currently the same) - Fix selftests undefined behavior x86: - Fix a restriction that the guest can't program a PMU event whose encoding matches an architectural event that isn't included in the guest CPUID. The enumeration of an architectural event only says that if a CPU supports an architectural event, then the event can be programmed *using the architectural encoding*. The enumeration does NOT say anything about the encoding when the CPU doesn't report support the event *in general*. It might support it, and it might support it using the same encoding that made it into the architectural PMU spec - Fix a variety of bugs in KVM's emulation of RDPMC (more details on individual commits) and add a selftest to verify KVM correctly emulates RDMPC, counter availability, and a variety of other PMC-related behaviors that depend on guest CPUID and therefore are easier to validate with selftests than with custom guests (aka kvm-unit-tests) - Zero out PMU state on AMD if the virtual PMU is disabled, it does not cause any bug but it wastes time in various cases where KVM would check if a PMC event needs to be synthesized - Optimize triggering of emulated events, with a nice ~10% performance improvement in VM-Exit microbenchmarks when a vPMU is exposed to the guest - Tighten the check for "PMI in guest" to reduce false positives if an NMI arrives in the host while KVM is handling an IRQ VM-Exit - Fix a bug where KVM would report stale/bogus exit qualification information when exiting to userspace with an internal error exit code - Add a VMX flag in /proc/cpuinfo to report 5-level EPT support - Rework TDP MMU root unload, free, and alloc to run with mmu_lock held for read, e.g. to avoid serializing vCPUs when userspace deletes a memslot - Tear down TDP MMU page tables at 4KiB granularity (used to be 1GiB). KVM doesn't support yielding in the middle of processing a zap, and 1GiB granularity resulted in multi-millisecond lags that are quite impolite for CONFIG_PREEMPT kernels - Allocate write-tracking metadata on-demand to avoid the memory overhead when a kernel is built with i915 virtualization support but the workloads use neither shadow paging nor i915 virtualization - Explicitly initialize a variety of on-stack variables in the emulator that triggered KMSAN false positives - Fix the debugregs ABI for 32-bit KVM - Rework the "force immediate exit" code so that vendor code ultimately decides how and when to force the exit, which allowed some optimization for both Intel and AMD - Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if vCPU creation ultimately failed, causing extra unnecessary work - Cleanup the logic for checking if the currently loaded vCPU is in-kernel - Harden against underflowing the active mmu_notifier invalidation count, so that "bad" invalidations (usually due to bugs elsehwere in the kernel) are detected earlier and are less likely to hang the kernel x86 Xen emulation: - Overlay pages can now be cached based on host virtual address, instead of guest physical addresses. This removes the need to reconfigure and invalidate the cache if the guest changes the gpa but the underlying host virtual address remains the same - When possible, use a single host TSC value when computing the deadline for Xen timers in order to improve the accuracy of the timer emulation - Inject pending upcall events when the vCPU software-enables its APIC to fix a bug where an upcall can be lost (and to follow Xen's behavior) - Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen events fails, e.g. if the guest has aliased xAPIC IDs RISC-V: - Support exception and interrupt handling in selftests - New self test for RISC-V architectural timer (Sstc extension) - New extension support (Ztso, Zacas) - Support userspace emulation of random number seed CSRs ARM: - Infrastructure for building KVM's trap configuration based on the architectural features (or lack thereof) advertised in the VM's ID registers - Support for mapping vfio-pci BARs as Normal-NC (vaguely similar to x86's WC) at stage-2, improving the performance of interacting with assigned devices that can tolerate it - Conversion of KVM's representation of LPIs to an xarray, utilized to address serialization some of the serialization on the LPI injection path - Support for _architectural_ VHE-only systems, advertised through the absence of FEAT_E2H0 in the CPU's ID register - Miscellaneous cleanups, fixes, and spelling corrections to KVM and selftests LoongArch: - Set reserved bits as zero in CPUCFG - Start SW timer only when vcpu is blocking - Do not restart SW timer when it is expired - Remove unnecessary CSR register saving during enter guest - Misc cleanups and fixes as usual Generic: - Clean up Kconfig by removing CONFIG_HAVE_KVM, which was basically always true on all architectures except MIPS (where Kconfig determines the available depending on CPU capabilities). It is replaced either by an architecture-dependent symbol for MIPS, and IS_ENABLED(CONFIG_KVM) everywhere else - Factor common "select" statements in common code instead of requiring each architecture to specify it - Remove thoroughly obsolete APIs from the uapi headers - Move architecture-dependent stuff to uapi/asm/kvm.h - Always flush the async page fault workqueue when a work item is being removed, especially during vCPU destruction, to ensure that there are no workers running in KVM code when all references to KVM-the-module are gone, i.e. to prevent a very unlikely use-after-free if kvm.ko is unloaded - Grab a reference to the VM's mm_struct in the async #PF worker itself instead of gifting the worker a reference, so that there's no need to remember to *conditionally* clean up after the worker Selftests: - Reduce boilerplate especially when utilize selftest TAP infrastructure - Add basic smoke tests for SEV and SEV-ES, along with a pile of library support for handling private/encrypted/protected memory - Fix benign bugs where tests neglect to close() guest_memfd files" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (246 commits) selftests: kvm: remove meaningless assignments in Makefiles KVM: riscv: selftests: Add Zacas extension to get-reg-list test RISC-V: KVM: Allow Zacas extension for Guest/VM KVM: riscv: selftests: Add Ztso extension to get-reg-list test RISC-V: KVM: Allow Ztso extension for Guest/VM RISC-V: KVM: Forward SEED CSR access to user space KVM: riscv: selftests: Add sstc timer test KVM: riscv: selftests: Change vcpu_has_ext to a common function KVM: riscv: selftests: Add guest helper to get vcpu id KVM: riscv: selftests: Add exception handling support LoongArch: KVM: Remove unnecessary CSR register saving during enter guest LoongArch: KVM: Do not restart SW timer when it is expired LoongArch: KVM: Start SW timer only when vcpu is blocking LoongArch: KVM: Set reserved bits as zero in CPUCFG KVM: selftests: Explicitly close guest_memfd files in some gmem tests KVM: x86/xen: fix recursive deadlock in timer injection KVM: pfncache: simplify locking and make more self-contained KVM: x86/xen: remove WARN_ON_ONCE() with false positives in evtchn delivery KVM: x86/xen: inject vCPU upcall vector when local APIC is enabled KVM: x86/xen: improve accuracy of Xen timers ...

Merge tag 'kvm-x86-xen-6.9' of https://github.com/kvm-x86/linux into HEAD

2024-03-11T14:42:55Z

KVM Xen and pfncache changes for 6.9: - Rip out the half-baked support for using gfn_to_pfn caches to manage pages that are "mapped" into guests via physical addresses. - Add support for using gfn_to_pfn caches with only a host virtual address, i.e. to bypass the "gfn" stage of the cache. The primary use case is overlay pages, where the guest may change the gfn used to reference the overlay page, but the backing hva+pfn remains the same. - Add an ioctl() to allow mapping Xen's shared_info page using an hva instead of a gpa, so that userspace doesn't need to reconfigure and invalidate the cache/mapping if the guest changes the gpa (but userspace keeps the resolved hva the same). - When possible, use a single host TSC value when computing the deadline for Xen timers in order to improve the accuracy of the timer emulation. - Inject pending upcall events when the vCPU software-enables its APIC to fix a bug where an upcall can be lost (and to follow Xen's behavior). - Fall back to the slow path instead of warning if "fast" IRQ delivery of Xen events fails, e.g. if the guest has aliased xAPIC IDs. - Extend gfn_to_pfn_cache's mutex to cover (de)activation (in addition to refresh), and drop a now-redundant acquisition of xen_lock (that was protecting the shared_info cache) to fix a deadlock due to recursively acquiring xen_lock.

Merge tag 'kvm-x86-misc-6.9' of https://github.com/kvm-x86/linux into HEAD

2024-03-11T14:24:56Z

KVM x86 misc changes for 6.9: - Explicitly initialize a variety of on-stack variables in the emulator that triggered KMSAN false positives (though in fairness in KMSAN, it's comically difficult to see that the uninitialized memory is never truly consumed). - Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading DR6 and DR7. - Rework the "force immediate exit" code so that vendor code ultimately decides how and when to force the exit. This allows VMX to further optimize handling preemption timer exits, and allows SVM to avoid sending a duplicate IPI (SVM also has a need to force an exit). - Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if vCPU creation ultimately failed, and add WARN to guard against similar bugs. - Provide a dedicated arch hook for checking if a different vCPU was in-kernel (for directed yield), and simplify the logic for checking if the currently loaded vCPU is in-kernel. - Misc cleanups and fixes.

Merge tag 'kvm-x86-asyncpf-6.9' of https://github.com/kvm-x86/linux into HEAD

2024-03-11T14:22:41Z

KVM async page fault changes for 6.9: - Always flush the async page fault workqueue when a work item is being removed, especially during vCPU destruction, to ensure that there are no workers running in KVM code when all references to KVM-the-module are gone, i.e. to prevent a use-after-free if kvm.ko is unloaded. - Grab a reference to the VM's mm_struct in the async #PF worker itself instead of gifting the worker a reference, e.g. so that there's no need to remember to *conditionally* clean up after the worker.

KVM: Get rid of return value from kvm_arch_create_vm_debugfs()

2024-02-23T21:44:58Z

The general expectation with debugfs is that any initialization failure is nonfatal. Nevertheless, kvm_arch_create_vm_debugfs() allows implementations to return an error and kvm_create_vm_debugfs() allows that to fail VM creation. Change to a void return to discourage architectures from making debugfs failures fatal for the VM. Seems like everyone already had the right idea, as all implementations already return 0 unconditionally. Acked-by: Marc Zyngier Acked-by: Paolo Bonzini Link: https://lore.kernel.org/r/20240216155941.2029458-1-oliver.upton@linux.dev Signed-off-by: Oliver Upton

KVM: x86/mmu: Retry fault before acquiring mmu_lock if mapping is changing

2024-02-23T18:14:34Z

Retry page faults without acquiring mmu_lock, and without even faulting the page into the primary MMU, if the resolved gfn is covered by an active invalidation. Contending for mmu_lock is especially problematic on preemptible kernels as the mmu_notifier invalidation task will yield mmu_lock (see rwlock_needbreak()), delay the in-progress invalidation, and ultimately increase the latency of resolving the page fault. And in the worst case scenario, yielding will be accompanied by a remote TLB flush, e.g. if the invalidation covers a large range of memory and vCPUs are accessing addresses that were already zapped. Faulting the page into the primary MMU is similarly problematic, as doing so may acquire locks that need to be taken for the invalidation to complete (the primary MMU has finer grained locks than KVM's MMU), and/or may cause unnecessary churn (getting/putting pages, marking them accessed, etc). Alternatively, the yielding issue could be mitigated by teaching KVM's MMU iterators to perform more work before yielding, but that wouldn't solve the lock contention and would negatively affect scenarios where a vCPU is trying to fault in an address that is NOT covered by the in-progress invalidation. Add a dedicated lockess version of the range-based retry check to avoid false positives on the sanity check on start+end WARN, and so that it's super obvious that checking for a racing invalidation without holding mmu_lock is unsafe (though obviously useful). Wrap mmu_invalidate_in_progress in READ_ONCE() to ensure that pre-checking invalidation in a loop won't put KVM into an infinite loop, e.g. due to caching the in-progress flag and never seeing it go to '0'. Force a load of mmu_invalidate_seq as well, even though it isn't strictly necessary to avoid an infinite loop, as doing so improves the probability that KVM will detect an invalidation that already completed before acquiring mmu_lock and bailing anyways. Do the pre-check even for non-preemptible kernels, as waiting to detect the invalidation until mmu_lock is held guarantees the vCPU will observe the worst case latency in terms of handling the fault, and can generate even more mmu_lock contention. E.g. the vCPU will acquire mmu_lock, detect retry, drop mmu_lock, re-enter the guest, retake the fault, and eventually re-acquire mmu_lock. This behavior is also why there are no new starvation issues due to losing the fairness guarantees provided by rwlocks: if the vCPU needs to retry, it _must_ drop mmu_lock, i.e. waiting on mmu_lock doesn't guarantee forward progress in the face of _another_ mmu_notifier invalidation event. Note, adding READ_ONCE() isn't entirely free, e.g. on x86, the READ_ONCE() may generate a load into a register instead of doing a direct comparison (MOV+TEST+Jcc instead of CMP+Jcc), but practically speaking the added cost is a few bytes of code and maaaaybe a cycle or three. Reported-by: Yan Zhao Closes: https://lore.kernel.org/all/ZNnPF4W26ZbAyGto@yzhao56-desk.sh.intel.com Reported-by: Friedrich Weber Cc: Kai Huang Cc: Yan Zhao Cc: Yuan Yao Cc: Xu Yilun Acked-by: Kai Huang Reviewed-by: Yan Zhao Link: https://lore.kernel.org/r/20240222012640.2820927-1-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: Add dedicated arch hook for querying if vCPU was preempted in-kernel

2024-02-23T00:26:26Z

Plumb in a dedicated hook for querying whether or not a vCPU was preempted in-kernel. Unlike literally every other architecture, x86's VMX can check if a vCPU is in kernel context if and only if the vCPU is loaded on the current pCPU. x86's kvm_arch_vcpu_in_kernel() works around the limitation by querying kvm_get_running_vcpu() and redirecting to vcpu->arch.preempted_in_kernel as needed. But that's unnecessary, confusing, and fragile, e.g. x86 has had at least one bug where KVM incorrectly used a stale preempted_in_kernel. No functional change intended. Reviewed-by: Yuan Yao Link: https://lore.kernel.org/r/20240110003938.490206-2-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA

2024-02-20T15:37:46Z

Some pfncache pages may actually be overlays on guest memory that have a fixed HVA within the VMM. It's pointless to invalidate such cached mappings if the overlay is moved so allow a cache to be activated directly with the HVA to cater for such cases. A subsequent patch will make use of this facility. Signed-off-by: Paul Durrant Reviewed-by: David Woodhouse Link: https://lore.kernel.org/r/20240215152916.1158-10-paul@xen.org Signed-off-by: Sean Christopherson

KVM: s390: Refactor kvm_is_error_gpa() into kvm_is_gpa_in_memslot()

2024-02-20T15:37:45Z

Rename kvm_is_error_gpa() to kvm_is_gpa_in_memslot() and invert the polarity accordingly in order to (a) free up kvm_is_error_gpa() to match with kvm_is_error_{hva,page}(), and (b) to make it more obvious that the helper is doing a memslot lookup, i.e. not simply checking for INVALID_GPA. No functional change intended. Link: https://lore.kernel.org/r/20240215152916.1158-9-paul@xen.org Signed-off-by: Sean Christopherson

KVM: pfncache: remove KVM_GUEST_USES_PFN usage

2024-02-20T15:37:43Z

As noted in [1] the KVM_GUEST_USES_PFN usage flag is never set by any callers of kvm_gpc_init(), and for good reason: the implementation is incomplete/broken. And it's not clear that there will ever be a user of KVM_GUEST_USES_PFN, as coordinating vCPUs with mmu_notifier events is non-trivial. Remove KVM_GUEST_USES_PFN and all related code, e.g. dropping KVM_GUEST_USES_PFN also makes the 'vcpu' argument redundant, to avoid having to reason about broken code as __kvm_gpc_refresh() evolves. Moreover, all existing callers specify KVM_HOST_USES_PFN so the usage check in hva_to_pfn_retry() and hence the 'usage' argument to kvm_gpc_init() are also redundant. [1] https://lore.kernel.org/all/ZQiR8IpqOZrOpzHC@google.com Signed-off-by: Paul Durrant Reviewed-by: David Woodhouse Link: https://lore.kernel.org/r/20240215152916.1158-6-paul@xen.org [sean: explicitly call out that guest usage is incomplete] Signed-off-by: Sean Christopherson