linux.git/tools/testing/selftests/kvm/demand_paging_test.c, branch master

KVM: selftests: Add kvm_gettid() wrapper and convert users

2026-07-07T18:24:44+00:00

Add a KVM wrapper for the gettid() syscall so that tests don't have to open code the syscall() themselves. Unfortunately, not all flavors of libc that KVM selftests support provide gettid(). Convert all existing users of the syscall to the new wrapper. Note, per the gettid() manpage[1], "This call is always successful", i.e. prefixing kvm_ to the syscall name is aligned with the goal of providing syscall wrappers that guarantee success. No functional changes intended. Link: https://man7.org/linux/man-pages/man2/gettid.2.html [1] Suggested-by: Sean Christopherson Signed-off-by: Josh Hilke [sean: massage changelog] Link: https://patch.msgid.link/20260626213534.3866178-16-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Use u64 instead of uint64_t

2026-04-20T21:54:16+00:00

Use u64 instead of uint64_t to make the KVM selftests code more concise and more similar to the kernel (since selftests are primarily developed by kernel developers). This commit was generated with the following command: git ls-files tools/testing/selftests/kvm | xargs sed -i 's/uint64_t/u64/g' Then by manually adjusting whitespace to make checkpatch.pl happy. Include in include/kvm_util_types.h, iinclude/test_util.h, and include/x86/pmu.h to pick up the tools-defined u64. Arguably, all headers (especially kvm_util_types.h) should have already been including stdint.h to get uint64_t from the libc headers, but the missing dependency only rears its head once KVM uses u64 instead of uint64_t. No functional change intended. Signed-off-by: David Matlack [sean: rename pread_uint64() => pread_u64, expand on types.h include] Link: https://patch.msgid.link/20260420212004.3938325-5-seanjc@google.com Signed-off-by: Sean Christopherson

Merge tag 'kvm-x86-selftests_utils-6.10' of https://github.com/kvm-x86/linux into HEAD

2024-05-12T07:18:11+00:00

KVM selftests treewide updates for 6.10: - Define _GNU_SOURCE for all selftests to fix a warning that was introduced by a change to kselftest_harness.h late in the 6.9 cycle, and because forcing every test to #define _GNU_SOURCE is painful. - Provide a global psuedo-RNG instance for all tests, so that library code can generate random, but determinstic numbers. - Use the global pRNG to randomly force emulation of select writes from guest code on x86, e.g. to help validate KVM's emulation of locked accesses. - Rename kvm_util_base.h back to kvm_util.h, as the weird layer of indirection was added purely to avoid manually #including ucall_common.h in a handful of locations. - Allocate and initialize x86's GDT, IDT, TSS, segments, and default exception handlers at VM creation, instead of forcing tests to manually trigger the related setup.

Revert "kvm: selftests: move base kvm_util.h declarations to kvm_util_base.h"

2024-04-29T19:54:13+00:00

Effectively revert the movement of code from kvm_util.h => kvm_util_base.h, as the TL;DR of the justification for the move was to avoid #idefs and/or circular dependencies between what ended up being ucall_common.h and what was (and now again, is), kvm_util.h. But avoiding #ifdef and circular includes is trivial: don't do that. The cost of removing kvm_util_base.h is a few extra includes of ucall_common.h, but that cost is practically nothing. On the other hand, having a "base" version of a header that is really just the header itself is confusing, and makes it weird/hard to choose names for headers that actually are "base" headers, e.g. to hold core KVM selftests typedefs. For all intents and purposes, this reverts commit 7d9a662ed9f0403e7b94940dceb81552b8edb931. Reviewed-by: Ackerley Tng Link: https://lore.kernel.org/r/20240314232637.2538648-2-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Define _GNU_SOURCE for all selftests code

2024-04-29T19:49:10+00:00

Define _GNU_SOURCE is the base CFLAGS instead of relying on selftests to manually #define _GNU_SOURCE, which is repetitive and error prone. E.g. kselftest_harness.h requires _GNU_SOURCE for asprintf(), but if a selftest includes kvm_test_harness.h after stdio.h, the include guards result in the effective version of stdio.h consumed by kvm_test_harness.h not defining asprintf(): In file included from x86_64/fix_hypercall_test.c:12: In file included from include/kvm_test_harness.h:11: ../kselftest_harness.h:1169:2: error: call to undeclared function 'asprintf'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] 1169 | asprintf(&test_name, "%s%s%s.%s", f->name, | ^ When including the rseq selftest's "library" code, #undef _GNU_SOURCE so that rseq.c controls whether or not it wants to build with _GNU_SOURCE. Reported-by: Muhammad Usama Anjum Acked-by: Claudio Imbrenda Acked-by: Oliver Upton Acked-by: Anup Patel Reviewed-by: Muhammad Usama Anjum Link: https://lore.kernel.org/r/20240423190308.2883084-1-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Use EPOLL in userfaultfd_util reader threads

2024-04-09T21:30:14+00:00

With multiple reader threads POLLing a single UFFD, the demand paging test suffers from the thundering herd problem: performance degrades as the number of reader threads is increased. Solve this issue [1] by switching the the polling mechanism to EPOLL + EPOLLEXCLUSIVE. Also, change the error-handling convention of uffd_handler_thread_fn. Instead of just printing errors and returning early from the polling loop, check for them via TEST_ASSERT(). "return NULL" is reserved for a successful exit from uffd_handler_thread_fn, i.e. one triggered by a write to the exit pipe. Performance samples generated by the command in [2] are given below. Num Reader Threads, Paging Rate (POLL), Paging Rate (EPOLL) 1 249k 185k 2 201k 235k 4 186k 155k 16 150k 217k 32 89k 198k [1] Single-vCPU performance does suffer somewhat. [2] ./demand_paging_test -u MINOR -s shmem -v 4 -o -r Signed-off-by: Anish Moorthy Acked-by: James Houghton Link: https://lore.kernel.org/r/20240215235405.368539-13-amoorthy@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Allow many vCPUs and reader threads per UFFD in demand paging test

2024-04-09T21:28:53+00:00

At the moment, demand_paging_test does not support profiling/testing multiple vCPU threads concurrently faulting on a single uffd because (a) "-u" (run test in userfaultfd mode) creates a uffd for each vCPU's region, so that each uffd services a single vCPU thread. (b) "-u -o" (userfaultfd mode + overlapped vCPU memory accesses) simply doesn't work: the test tries to register the same memory to multiple uffds, causing an error. Add support for many vcpus per uffd by (1) Keeping "-u" behavior unchanged. (2) Making "-u -a" create a single uffd for all of guest memory. (3) Making "-u -o" implicitly pass "-a", solving the problem in (b). In cases (2) and (3) all vCPU threads fault on a single uffd. With potentially multiple vCPUs per UFFD, it makes sense to allow configuring the number of reader threads per UFFD as well: add the "-r" flag to do so. Signed-off-by: Anish Moorthy Acked-by: James Houghton Link: https://lore.kernel.org/r/20240215235405.368539-12-amoorthy@google.com [sean: fix kernel style violations, use calloc() for arrays] Signed-off-by: Sean Christopherson

KVM: selftests: Report per-vcpu demand paging rate from demand paging test

2024-04-09T21:16:48+00:00

Using the overall demand paging rate to measure performance can be slightly misleading when vCPU accesses are not overlapped. Adding more vCPUs will (usually) increase the overall demand paging rate even if performance remains constant or even degrades on a per-vcpu basis. As such, it makes sense to report both the total and per-vcpu paging rates. Signed-off-by: Anish Moorthy Link: https://lore.kernel.org/r/20240215235405.368539-11-amoorthy@google.com [sean: fix formatting] Signed-off-by: Sean Christopherson

KVM: selftests: Remove redundant newlines

2024-01-29T16:39:14+00:00

TEST_* functions append their own newline. Remove newlines from TEST_* callsites to avoid extra newlines in output. Signed-off-by: Andrew Jones Link: https://lore.kernel.org/r/20231206170241.82801-8-ajones@ventanamicro.com Signed-off-by: Sean Christopherson

KVM: selftests: Allow specify physical cpu list in demand paging test

2023-06-07T00:29:49+00:00

Mimic the dirty log test and allow the user to pin demand paging test tasks to physical CPUs. Put the help message into a general helper as suggested by Sean. Signed-off-by: Peter Xu [sean: rebase, tweak arg ordering, add "print" to helper, print program name] Link: https://lore.kernel.org/r/20230607001226.1398889-1-seanjc@google.com Signed-off-by: Sean Christopherson