kernel/linux.git/tools/testing/selftests/kvm/include/test_util.h, branch v6.18.22

KVM: selftests: Add wrapper macro to handle and assert on expected SIGBUS

2025-10-10T21:25:29+00:00

Extract the guest_memfd test's SIGBUS handling functionality into a common TEST_EXPECT_SIGBUS() macro in anticipation of adding more SIGBUS testcases. Eating a SIGBUS isn't terrible difficult, but it requires a non-trivial amount of boilerplate code, and using a macro allows selftests to print out the exact action that failed to generate a SIGBUS without the developer needing to remember to add a useful error message. Explicitly mark the SIGBUS handler as "used", as gcc-14 at least likes to discard the function before linking. Opportunistically use TEST_FAIL(...) instead of TEST_ASSERT(false, ...), and fix the write path of the guest_memfd test to use the local "val" instead of hardcoding the literal value a second time. Suggested-by: Ackerley Tng Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Reviewed-by: Lisa Wang Tested-by: Lisa Wang Link: https://lore.kernel.org/r/20251003232606.4070510-12-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: access_tracking_perf_test: Add option to skip the sanity check

2025-05-16T18:45:12+00:00

Add an option to skip sanity check of number of still idle pages, and set it by default to skip, in case hypervisor or NUMA balancing is detected. Signed-off-by: Maxim Levitsky Co-developed-by: James Houghton Signed-off-by: James Houghton Reviewed-by: Maxim Levitsky Link: https://lore.kernel.org/r/20250508184649.2576210-3-jthoughton@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Add printf attribute to _no_printf()

2025-01-08T20:56:31+00:00

Annotate the KVM selftests' _no_printf() with the printf format attribute so that the compiler can help check parameters provided to pr_debug() and pr_info() irrespective of DEBUG and QUIET being defined. [reinette: move attribute right after storage class, rework changelog] Signed-off-by: Isaku Yamahata Signed-off-by: Reinette Chatre Link: https://lore.kernel.org/r/898ec01580f6f4af5655805863239d6dce0d3fb3.1734128510.git.reinette.chatre@intel.com Signed-off-by: Sean Christopherson

KVM: selftests: Provide an API for getting a random bool from an RNG

2024-04-29T19:50:42+00:00

Move memstress' random bool logic into common code to avoid reinventing the wheel for basic yes/no decisions. Provide an outer wrapper to handle the basic/common case of just wanting a 50/50 chance of something happening. Link: https://lore.kernel.org/r/20240314185459.2439072-3-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: selftests: Provide a global pseudo-RNG instance for all tests

2024-04-29T19:50:41+00:00

Add a global guest_random_state instance, i.e. a pseudo-RNG, so that an RNG is available for *all* tests. This will allow randomizing behavior in core library code, e.g. x86 will utilize the pRNG to conditionally force emulation of writes from within common guest code. To allow for deterministic runs, and to be compatible with existing tests, allow tests to override the seed used to initialize the pRNG. Note, the seed *must* be overwritten before a VM is created in order for the seed to take effect, though it's perfectly fine for a test to initialize multiple VMs with different seeds. And as evidenced by memstress_guest_code(), it's also a-ok to instantiate more RNGs using the global seed (or a modified version of it). The goal of the global RNG is purely to ensure that _a_ source of random numbers is available, it doesn't have to be the _only_ RNG. Link: https://lore.kernel.org/r/20240314185459.2439072-2-seanjc@google.com Signed-off-by: Sean Christopherson

KVM: arm64: selftests: Split arch_timer test code

2024-02-26T04:43:58+00:00

Split the arch-neutral test code out of aarch64/arch_timer.c and put them into a common arch_timer.c. This is a preparation to share timer test codes in riscv. Suggested-by: Andrew Jones Signed-off-by: Haibo Xu Reviewed-by: Andrew Jones Signed-off-by: Anup Patel

KVM: selftests: Generalize check_clocksource() from kvm_clock_test

2024-02-01T16:58:13+00:00

Several existing x86 selftests need to check that the underlying system clocksource is TSC or based on TSC but every test implements its own check. As a first step towards unification, extract check_clocksource() from kvm_clock_test and split it into two functions: arch-neutral 'sys_get_cur_clocksource()' and x86-specific 'sys_clocksource_is_tsc()'. Fix a couple of pre-existing issues in kvm_clock_test: memory leakage in check_clocksource() and using TEST_ASSERT() instead of TEST_REQUIRE(). The change also makes the test fail when system clocksource can't be read from sysfs. Signed-off-by: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20240109141121.1619463-2-vkuznets@redhat.com [sean: eliminate if-elif pattern just to set a bool true] Signed-off-by: Sean Christopherson

KVM: selftests: Annotate guest ucall, printf, and assert helpers with __printf()

2023-12-01T16:15:41+00:00

Annotate guest printf helpers with __printf() so that the compiler will warn about incorrect formatting at compile time (see git log for how easy it is to screw up with the formatting). Suggested-by: Maxim Levitsky Link: https://lore.kernel.org/r/20231129224916.532431-5-seanjc@google.com Signed-off-by: Sean Christopherson

Merge branch 'kvm-guestmemfd' into HEAD

2023-11-14T13:31:31+00:00

Introduce several new KVM uAPIs to ultimately create a guest-first memory subsystem within KVM, a.k.a. guest_memfd. Guest-first memory allows KVM to provide features, enhancements, and optimizations that are kludgly or outright impossible to implement in a generic memory subsystem. The core KVM ioctl() for guest_memfd is KVM_CREATE_GUEST_MEMFD, which similar to the generic memfd_create(), creates an anonymous file and returns a file descriptor that refers to it. Again like "regular" memfd files, guest_memfd files live in RAM, have volatile storage, and are automatically released when the last reference is dropped. The key differences between memfd files (and every other memory subystem) is that guest_memfd files are bound to their owning virtual machine, cannot be mapped, read, or written by userspace, and cannot be resized. guest_memfd files do however support PUNCH_HOLE, which can be used to convert a guest memory area between the shared and guest-private states. A second KVM ioctl(), KVM_SET_MEMORY_ATTRIBUTES, allows userspace to specify attributes for a given page of guest memory. In the long term, it will likely be extended to allow userspace to specify per-gfn RWX protections, including allowing memory to be writable in the guest without it also being writable in host userspace. The immediate and driving use case for guest_memfd are Confidential (CoCo) VMs, specifically AMD's SEV-SNP, Intel's TDX, and KVM's own pKVM. For such use cases, being able to map memory into KVM guests without requiring said memory to be mapped into the host is a hard requirement. While SEV+ and TDX prevent untrusted software from reading guest private data by encrypting guest memory, pKVM provides confidentiality and integrity *without* relying on memory encryption. In addition, with SEV-SNP and especially TDX, accessing guest private memory can be fatal to the host, i.e. KVM must be prevent host userspace from accessing guest memory irrespective of hardware behavior. Long term, guest_memfd may be useful for use cases beyond CoCo VMs, for example hardening userspace against unintentional accesses to guest memory. As mentioned earlier, KVM's ABI uses userspace VMA protections to define the allow guest protection (with an exception granted to mapping guest memory executable), and similarly KVM currently requires the guest mapping size to be a strict subset of the host userspace mapping size. Decoupling the mappings sizes would allow userspace to precisely map only what is needed and with the required permissions, without impacting guest performance. A guest-first memory subsystem also provides clearer line of sight to things like a dedicated memory pool (for slice-of-hardware VMs) and elimination of "struct page" (for offload setups where userspace _never_ needs to DMA from or into guest memory). guest_memfd is the result of 3+ years of development and exploration; taking on memory management responsibilities in KVM was not the first, second, or even third choice for supporting CoCo VMs. But after many failed attempts to avoid KVM-specific backing memory, and looking at where things ended up, it is quite clear that of all approaches tried, guest_memfd is the simplest, most robust, and most extensible, and the right thing to do for KVM and the kernel at-large. The "development cycle" for this version is going to be very short; ideally, next week I will merge it as is in kvm/next, taking this through the KVM tree for 6.8 immediately after the end of the merge window. The series is still based on 6.6 (plus KVM changes for 6.7) so it will require a small fixup for changes to get_file_rcu() introduced in 6.7 by commit 0ede61d8589c ("file: convert to SLAB_TYPESAFE_BY_RCU"). The fixup will be done as part of the merge commit, and most of the text above will become the commit message for the merge. Pending post-merge work includes: - hugepage support - looking into using the restrictedmem framework for guest memory - introducing a testing mechanism to poison memory, possibly using the same memory attributes introduced here - SNP and TDX support There are two non-KVM patches buried in the middle of this series: fs: Rename anon_inode_getfile_secure() and anon_inode_getfd_secure() mm: Add AS_UNMOVABLE to mark mapping as completely unmovable The first is small and mostly suggested-by Christian Brauner; the second a bit less so but it was written by an mm person (Vlastimil Babka).

KVM: selftests: Add support for creating private memslots

2023-11-14T13:01:06+00:00

Add support for creating "private" memslots via KVM_CREATE_GUEST_MEMFD and KVM_SET_USER_MEMORY_REGION2. Make vm_userspace_mem_region_add() a wrapper to its effective replacement, vm_mem_add(), so that private memslots are fully opt-in, i.e. don't require update all tests that add memory regions. Pivot on the KVM_MEM_PRIVATE flag instead of the validity of the "gmem" file descriptor so that simple tests can let vm_mem_add() do the heavy lifting of creating the guest memfd, but also allow the caller to pass in an explicit fd+offset so that fancier tests can do things like back multiple memslots with a single file. If the caller passes in a fd, dup() the fd so that (a) __vm_mem_region_delete() can close the fd associated with the memory region without needing yet another flag, and (b) so that the caller can safely close its copy of the fd without having to first destroy memslots. Co-developed-by: Ackerley Tng Signed-off-by: Ackerley Tng Signed-off-by: Sean Christopherson Message-Id: <20231027182217.3615211-27-seanjc@google.com> Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Signed-off-by: Paolo Bonzini