Changes in trace_remote.c

01f492e1817e858d1712f2489d0afbaa552f417b - Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Fri, 17 Apr 2026 16:18:03 +0200

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvmPull kvm updates from Paolo Bonzini: "Arm: - Add support for tracing in the standalone EL2 hypervisor code, which should help both debugging and performance analysis. This uses the new infrastructure for 'remote' trace buffers that can be exposed by non-kernel entities such as firmware, and which came through the tracing tree - Add support for GICv5 Per Processor Interrupts (PPIs), as the starting point for supporting the new GIC architecture in KVM - Finally add support for pKVM protected guests, where pages are unmapped from the host as they are faulted into the guest and can be shared back from the guest using pKVM hypercalls. Protected guests are created using a new machine type identifier. As the elusive guestmem has not yet delivered on its promises, anonymous memory is also supported This is only a first step towards full isolation from the host; for example, the CPU register state and DMA accesses are not yet isolated. Because this does not really yet bring fully what it promises, it is hidden behind CONFIG_ARM_PKVM_GUEST + 'kvm-arm.mode=protected', and also triggers TAINT_USER when a VM is created. Caveat emptor - Rework the dreaded user_mem_abort() function to make it more maintainable, reducing the amount of state being exposed to the various helpers and rendering a substantial amount of state immutable - Expand the Stage-2 page table dumper to support NV shadow page tables on a per-VM basis - Tidy up the pKVM PSCI proxy code to be slightly less hard to follow - Fix both SPE and TRBE in non-VHE configurations so that they do not generate spurious, out of context table walks that ultimately lead to very bad HW lockups - A small set of patches fixing the Stage-2 MMU freeing in error cases - Tighten-up accepted SMC immediate value to be only #0 for host SMCCC calls - The usual cleanups and other selftest churn LoongArch: - Use CSR_CRMD_PLV for kvm_arch_vcpu_in_kernel() - Add DMSINTC irqchip in kernel support RISC-V: - Fix steal time shared memory alignment checks - Fix vector context allocation leak - Fix array out-of-bounds in pmu_ctr_read() and pmu_fw_ctr_read_hi() - Fix double-free of sdata in kvm_pmu_clear_snapshot_area() - Fix integer overflow in kvm_pmu_validate_counter_mask() - Fix shift-out-of-bounds in make_xfence_request() - Fix lost write protection on huge pages during dirty logging - Split huge pages during fault handling for dirty logging - Skip CSR restore if VCPU is reloaded on the same core - Implement kvm_arch_has_default_irqchip() for KVM selftests - Factored-out ISA checks into separate sources - Added hideleg to struct kvm_vcpu_config - Factored-out VCPU config into separate sources - Support configuration of per-VM HGATP mode from KVM user space s390: - Support for ESA (31-bit) guests inside nested hypervisors - Remove restriction on memslot alignment, which is not needed anymore with the new gmap code - Fix LPSW/E to update the bear (which of course is the breaking event address register) x86: - Shut up various UBSAN warnings on reading module parameter before they were initialized - Don't zero-allocate page tables that are used for splitting hugepages in the TDP MMU, as KVM is guaranteed to set all SPTEs in the page table and thus write all bytes - As an optimization, bail early when trying to unsync 4KiB mappings if the target gfn can just be mapped with a 2MiB hugepage x86 generic: - Copy single-chunk MMIO write values into struct kvm_vcpu (more precisely struct kvm_mmio_fragment) to fix use-after-free stack bugs where KVM would dereference stack pointer after an exit to userspace - Clean up and comment the emulated MMIO code to try to make it easier to maintain (not necessarily "easy", but "easier") - Move VMXON+VMXOFF and EFER.SVME toggling out of KVM (not *all* of VMX and SVM enabling) as it is needed for trusted I/O - Advertise support for AVX512 Bit Matrix Multiply (BMM) instructions - Immediately fail the build if a required #define is missing in one of KVM's headers that is included multiple times - Reject SET_GUEST_DEBUG with -EBUSY if there's an already injected exception, mostly to prevent syzkaller from abusing the uAPI to trigger WARNs, but also because it can help prevent userspace from unintentionally crashing the VM - Exempt SMM from CPUID faulting on Intel, as per the spec - Misc hardening and cleanup changes x86 (AMD): - Fix and optimize IRQ window inhibit handling for AVIC; make it per-vCPU so that KVM doesn't prematurely re-enable AVIC if multiple vCPUs have to-be-injected IRQs - Clean up and optimize the OSVW handling, avoiding a bug in which KVM would overwrite state when enabling virtualization on multiple CPUs in parallel. This should not be a problem because OSVW should usually be the same for all CPUs - Drop a WARN in KVM_MEMORY_ENCRYPT_REG_REGION where KVM complains about a "too large" size based purely on user input - Clean up and harden the pinning code for KVM_MEMORY_ENCRYPT_REG_REGION - Disallow synchronizing a VMSA of an already-launched/encrypted vCPU, as doing so for an SNP guest will crash the host due to an RMP violation page fault - Overhaul KVM's APIs for detecting SEV+ guests so that VM-scoped queries are required to hold kvm->lock, and enforce it by lockdep. Fix various bugs where sev_guest() was not ensured to be stable for the whole duration of a function or ioctl - Convert a pile of kvm->lock SEV code to guard() - Play nicer with userspace that does not enable KVM_CAP_EXCEPTION_PAYLOAD, for which KVM needs to set CR2 and DR6 as a response to ioctls such as KVM_GET_VCPU_EVENTS (even if the payload would end up in EXITINFO2 rather than CR2, for example). Only set CR2 and DR6 when consumption of the payload is imminent, but on the other hand force delivery of the payload in all paths where userspace retrieves CR2 or DR6 - Use vcpu->arch.cr2 when updating vmcb12's CR2 on nested #VMEXIT instead of vmcb02->save.cr2. The value is out of sync after a save/restore or after a #PF is injected into L2 - Fix a class of nSVM bugs where some fields written by the CPU are not synchronized from vmcb02 to cached vmcb12 after VMRUN, and so are not up-to-date when saved by KVM_GET_NESTED_STATE - Fix a class of bugs where the ordering between KVM_SET_NESTED_STATE and KVM_SET_{S}REGS could cause vmcb02 to be incorrectly initialized after save+restore - Add a variety of missing nSVM consistency checks - Fix several bugs where KVM failed to correctly update VMCB fields on nested #VMEXIT - Fix several bugs where KVM failed to correctly synthesize #UD or #GP for SVM-related instructions - Add support for save+restore of virtualized LBRs (on SVM) - Refactor various helpers and macros to improve clarity and (hopefully) make the code easier to maintain - Aggressively sanitize fields when copying from vmcb12, to guard against unintentionally allowing L1 to utilize yet-to-be-defined features - Fix several bugs where KVM botched rAX legality checks when emulating SVM instructions. There are remaining issues in that KVM doesn't handle size prefix overrides for 64-bit guests - Fail emulation of VMRUN/VMLOAD/VMSAVE if mapping vmcb12 fails instead of somewhat arbitrarily synthesizing #GP (i.e. don't double down on AMD's architectural but sketchy behavior of generating #GP for "unsupported" addresses) - Cache all used vmcb12 fields to further harden against TOCTOU bugs x86 (Intel): - Drop obsolete branch hint prefixes from the VMX instruction macros - Use ASM_INPUT_RM() in __vmcs_writel() to coerce clang into using a register input when appropriate - Code cleanups guest_memfd: - Don't mark guest_memfd folios as accessed, as guest_memfd doesn't support reclaim, the memory is unevictable, and there is no storage to write back to LoongArch selftests: - Add KVM PMU test cases s390 selftests: - Enable more memory selftests x86 selftests: - Add support for Hygon CPUs in KVM selftests - Fix a bug in the MSR test where it would get false failures on AMD/Hygon CPUs with exactly one of RDPID or RDTSCP - Add an MADV_COLLAPSE testcase for guest_memfd as a regression test for a bug where the kernel would attempt to collapse guest_memfd folios against KVM's will"* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (373 commits) KVM: x86: use inlines instead of macros for is_sev_*guest x86/virt: Treat SVM as unsupported when running as an SEV+ guest KVM: SEV: Goto an existing error label if charging misc_cg for an ASID fails KVM: SVM: Move lock-protected allocation of SEV ASID into a separate helper KVM: SEV: use mutex guard in snp_handle_guest_req() KVM: SEV: use mutex guard in sev_mem_enc_unregister_region() KVM: SEV: use mutex guard in sev_mem_enc_ioctl() KVM: SEV: use mutex guard in snp_launch_update() KVM: SEV: Assert that kvm->lock is held when querying SEV+ support KVM: SEV: Document that checking for SEV+ guests when reclaiming memory is "safe" KVM: SEV: Hide "struct kvm_sev_info" behind CONFIG_KVM_AMD_SEV=y KVM: SEV: WARN on unhandled VM type when initializing VM KVM: LoongArch: selftests: Add PMU overflow interrupt test KVM: LoongArch: selftests: Add basic PMU event counting test KVM: LoongArch: selftests: Add cpucfg read/write helpers LoongArch: KVM: Add DMSINTC inject msi to vCPU LoongArch: KVM: Add DMSINTC device support LoongArch: KVM: Make vcpu_is_preempted() as a macro rather than function LoongArch: KVM: Move host CSR_GSTAT save and restore in context switch LoongArch: KVM: Move host CSR_EENTRY save and restore in context switch ... List of files: /linux/kernel/trace/trace_remote.c

e4bf304f000e6fcceaf60b1455a5124b783b3a66 - Merge tag 'trace-ringbuffer-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Thu, 16 Apr 2026 00:59:46 +0200

Merge tag 'trace-ringbuffer-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracePull ring-buffer updates from Steven Rostedt: - Add remote buffers for pKVM pKVM has a hypervisor component that is used to protect the guest from the host kernel. This hypervisor is a black box to the kernel as the kernel is to user space. The remote buffers are used to have a memory mapping between the hypervisor and the kernel where kernel may send commands to enable tracing within the hypervisor. Then the kernel will read this memory mapping just like user space can read the memory mapped ring buffer of the kernel tracing system. Since the hypervisor only has a single context, it doesn't need to worry about races between normal context, interrupt context and NMIs like the kernel does. The ring buffer it uses doesn't need to be as complex. The remote buffers are a simple version of the ring buffer that works in a single context. They are still per-CPU and use sub buffers. The data layout is the same as the kernel's ring buffer to share the same parsing. Currently, only ARM64 implements pKVM, but there's work to implement it also in x86. The remote buffer code is separated out from the ARM implementation so that it can be used in the future by x86. The ARM64 updates for pKVM is in the ARM/KVM tree and it merged in the remote buffers of this tree. - Make the backup instance non reusable The backup instance is a copy of the persistent ring buffer so that the persistent ring buffer could start recording again without using the data from the previous boot. The backup isn't for normal tracing. It is made read-only, and after it is consumed, it is automatically removed. - Have backup copy persistent instance before it starts recording To allow the persistent ring buffer to start recording from the kernel command line commands, move the copy of the backup instance to before the the command line options start recording. - Report header_page overwrite field as "char" and not "int' The rust parser of the header_page file was triggering a warning when it defined the overwrite variable as "int" but it was only a single byte in size. - Fix memory barriers for the trace_buffer CPU mask When a CPU comes online, the bit is set to allow readers to know that the CPU buffer is allocated. The bit is set after the allocation is done, and a smp_wmb() is performed after the allocation and before the setting of the bit. But instead of adding a smp_rmb() to all readers, since once a buffer is created for a CPU it is not deleted if that CPU goes offline, so this allocation is almost always done at boot up before any readers exist. If for the unlikely case where a CPU comes online for the first time after the system boot has finished, send an IPI to all CPUs to force the smp_rmb() for each CPU. - Show clock function being used in debugging ring buffer data When the ring buffer checks are enabled and the ring buffer detects an inconsistency in the times of the invents, print out the clock being used when the error occurred. There was a very hard to hit bug that would happen every so often and it ended up being only triggered when the jiffies clock was being used. If the bug showed the clock being used, it would have been much easier to find the problem (which was an internal function was being traced which caused the clock accounting to go off).* tag 'trace-ringbuffer-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (26 commits) ring-buffer: Prevent off-by-one array access in ring_buffer_desc_page() ring-buffer: Report header_page overwrite as char tracing: Allow backup to save persistent ring buffer before it starts tracing/Documentation: Add a section about backup instance tracing: Remove the backup instance automatically after read tracing: Make the backup instance non-reusable ring-buffer: Enforce read ordering of trace_buffer cpumask and buffers ring-buffer: Show what clock function is used on timestamp errors tracing: Check for undefined symbols in simple_ring_buffer tracing: load/unload page callbacks for simple_ring_buffer Documentation: tracing: Add tracing remotes tracing: selftests: Add trace remote tests tracing: Add a trace remote module for testing tracing: Introduce simple_ring_buffer ring-buffer: Export buffer_data_page and macros tracing: Add helpers to create trace remote events tracing: Add events/ root files to trace remotes tracing: Add events to trace remotes tracing: Add init callback to trace remotes tracing: Add non-consuming read to trace remotes ... List of files: /linux/kernel/trace/trace_remote.c

e74c3a8891c05f88eeb87121de7e12dc95766a4a - Merge tag 'kvmarm-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD

Mon, 13 Apr 2026 11:49:54 +0200

Merge tag 'kvmarm-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEADKVM/arm64 updates for 7.1* New features:- Add support for tracing in the standalone EL2 hypervisor code, which should help both debugging and performance analysis. This comes with a full infrastructure for 'remote' trace buffers that can be exposed by non-kernel entities such as firmware.- Add support for GICv5 Per Processor Interrupts (PPIs), as the starting point for supporting the new GIC architecture in KVM.- Finally add support for pKVM protected guests, with anonymous memory being used as a backing store. About time!* Improvements and bug fixes:- Rework the dreaded user_mem_abort() function to make it more maintainable, reducing the amount of state being exposed to the various helpers and rendering a substantial amount of state immutable.- Expand the Stage-2 page table dumper to support NV shadow page tables on a per-VM basis.- Tidy up the pKVM PSCI proxy code to be slightly less hard to follow.- Fix both SPE and TRBE in non-VHE configurations so that they do not generate spurious, out of context table walks that ultimately lead to very bad HW lockups.- A small set of patches fixing the Stage-2 MMU freeing in error cases.- Tighten-up accepted SMC immediate value to be only #0 for host SMCCC calls.- The usual cleanups and other selftest churn. List of files: /linux/kernel/trace/trace_remote.c

2de32a25a3f721052c9aaf753a65b96f63c2c7d9 - Merge branch kvm-arm64/hyp-tracing into kvmarm-master/next

Wed, 08 Apr 2026 13:21:51 +0200

Merge branch kvm-arm64/hyp-tracing into kvmarm-master/next* kvm-arm64/hyp-tracing: (40 commits) : . : EL2 tracing support, adding both 'remote' ring-buffer : infrastructure and the tracing itself, courtesy of : Vincent Donnefort. From the cover letter: : : "The growing set of features supported by the hypervisor in protected : mode necessitates debugging and profiling tools. Tracefs is the : ideal candidate for this task: : : * It is simple to use and to script. : : * It is supported by various tools, from the trace-cmd CLI to the : Android web-based perfetto. : : * The ring-buffer, where are stored trace events consists of linked : pages, making it an ideal structure for sharing between kernel and : hypervisor. : : This series first introduces a new generic way of creating remote events and : remote buffers. Then it adds support to the pKVM hypervisor." : . tracing: selftests: Extend hotplug testing for trace remotes tracing: Non-consuming read for trace remotes with an offline CPU tracing: Adjust cmd_check_undefined to show unexpected undefined symbols tracing: Restore accidentally removed SPDX tag KVM: arm64: avoid unused-variable warning tracing: Generate undef symbols allowlist for simple_ring_buffer KVM: arm64: tracing: add ftrace dependency tracing: add more symbols to whitelist tracing: Update undefined symbols allow list for simple_ring_buffer KVM: arm64: Fix out-of-tree build for nVHE/pKVM tracing tracing: selftests: Add hypervisor trace remote tests KVM: arm64: Add selftest event support to nVHE/pKVM hyp KVM: arm64: Add hyp_enter/hyp_exit events to nVHE/pKVM hyp KVM: arm64: Add event support to the nVHE/pKVM hyp and trace remote KVM: arm64: Add trace reset to the nVHE/pKVM hyp KVM: arm64: Sync boot clock with the nVHE/pKVM hyp KVM: arm64: Add trace remote for the nVHE/pKVM hyp KVM: arm64: Add tracing capability for the nVHE/pKVM hyp KVM: arm64: Support unaligned fixmap in the pKVM hyp KVM: arm64: Initialise hyp_nr_cpus for nVHE hyp ...Signed-off-by: Marc Zyngier List of files: /linux/kernel/trace/trace_remote.c

ce47b798ed1e44a6ae2c2966cdf7cba6b428083e - tracing: Non-consuming read for trace remotes with an offline CPU

Wed, 01 Apr 2026 06:50:59 +0200

tracing: Non-consuming read for trace remotes with an offline CPUWhen a trace_buffer is created while a CPU is offline, this CPU iscleared from the trace_buffer CPU mask, preventing the creation of anon-consuming iterator (ring_buffer_iter). For trace remotes, it meansthe iterator fails to be allocated (-ENOMEM) even though there areavailable ring buffers in the trace_buffer.For non-consuming reads of trace remotes, skip missing ring_buffer_iterto allow reading the available ring buffers.Acked-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Link: https://patch.msgid.link/20260401045100.3394299-2-vdonnefort@google.comSigned-off-by: Marc Zyngier List of files: /linux/kernel/trace/trace_remote.c

775cb093bc50649e83ad00ce5347d6fbd4aa8387 - tracing: Add events/ root files to trace remotes

Mon, 09 Mar 2026 17:24:56 +0100

tracing: Add events/ root files to trace remotesJust like for the kernel events directory, add 'enable', 'header_page'and 'header_event' at the root of the trace remote events/ directory.Link: https://patch.msgid.link/20260309162516.2623589-11-vdonnefort@google.comReviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) List of files: /linux/kernel/trace/trace_remote.c

072529158e604cc964feb78dcf094c6975828146 - tracing: Add events to trace remotes

Mon, 09 Mar 2026 17:24:55 +0100

tracing: Add events to trace remotesAn event is predefined point in the writer code that allows to logdata. Following the same scheme as kernel events, add remote events,described to user-space within the events/ tracefs directory found inthe corresponding trace remote.Remote events are expected to be described during the trace remoteregistration.Add also a .enable_event callback for trace_remote to toggle the eventlogging, if supported.Link: https://patch.msgid.link/20260309162516.2623589-10-vdonnefort@google.comReviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) List of files: /linux/kernel/trace/trace_remote.c

bf2ba0f8ca1af14aaaa765cbb93caf564d383aad - tracing: Add init callback to trace remotes

Mon, 09 Mar 2026 17:24:54 +0100

tracing: Add init callback to trace remotesAdd a .init call back so the trace remote callers can add entries to thetracefs directory.Link: https://patch.msgid.link/20260309162516.2623589-9-vdonnefort@google.comReviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) List of files: /linux/kernel/trace/trace_remote.c

330b0cceb30634864d1e9c661eb5524c52d70c07 - tracing: Add non-consuming read to trace remotes

Mon, 09 Mar 2026 17:24:53 +0100

tracing: Add non-consuming read to trace remotesAllow reading the trace file for trace remotes. This performs anon-consuming read of the trace buffer.Link: https://patch.msgid.link/20260309162516.2623589-8-vdonnefort@google.comReviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) List of files: /linux/kernel/trace/trace_remote.c

9af4ab0e11e336e2671d303ffcc6578e3546d9fc - tracing: Add reset to trace remotes

Mon, 09 Mar 2026 17:24:52 +0100

tracing: Add reset to trace remotesAllow to reset the trace remote buffer by writing to the Tracefs "trace"file. This is similar to the regular Tracefs interface.Link: https://patch.msgid.link/20260309162516.2623589-7-vdonnefort@google.comReviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) List of files: /linux/kernel/trace/trace_remote.c

96e43537af5461b26f50904c6055046ba65d742f - tracing: Introduce trace remotes

Mon, 09 Mar 2026 17:24:51 +0100

tracing: Introduce trace remotesA trace remote relies on ring-buffer remotes to read and controlcompatible tracing buffers, written by entity such as firmware orhypervisor.Add a Tracefs directory remotes/ that contains all instances of traceremotes. Each instance follows the same hierarchy as any other to easethe support by existing user-space tools.This currently does not provide any event support, which will comelater.Link: https://patch.msgid.link/20260309162516.2623589-6-vdonnefort@google.comReviewed-by: Steven Rostedt (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) List of files: /linux/kernel/trace/trace_remote.c