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Fri, 26 Jun 2026 14:35:41 -0700 (PDT) Date: Fri, 26 Jun 2026 14:35:17 -0700 In-Reply-To: <20260626213534.3866178-1-seanjc@google.com> Mime-Version: 1.0 References: <20260626213534.3866178-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.rc0.799.gd6f94ed593-goog Message-ID: <20260626213534.3866178-5-seanjc@google.com> Subject: [PATCH v8 04/20] KVM: selftests: Initialize the default/global pRNG during kvm_selftest_init() From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Oliver Upton , Sean Christopherson Cc: Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, David Matlack , Josh Hilke Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260626_143543_565862_A28144D2 X-CRM114-Status: GOOD ( 10.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Initialize the default kvm_rng during selftest initialization so that the pRNG can be used by tests before creating a VM. As pointed out by Sashiko, failure to actually initialize the generate makes it decidedly not random. Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/lib/kvm_util.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index 875030c22d07..1016865d3f7a 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c @@ -24,6 +24,13 @@ u32 kvm_random_seed; struct kvm_random_state kvm_rng; static u32 last_kvm_seed; +static void kvm_seed_rng(u32 seed) +{ + kvm_random_seed = last_kvm_seed = seed; + pr_info("Random seed: 0x%x\n", kvm_random_seed); + kvm_rng = new_kvm_random_state(kvm_random_seed); +} + static size_t vcpu_mmap_sz(void); int __open_path_or_exit(const char *path, int flags, const char *enoent_help) @@ -515,11 +522,9 @@ struct kvm_vm *__vm_create(struct vm_shape shape, u32 nr_runnable_vcpus, slot0 = memslot2region(vm, 0); ucall_init(vm, slot0->region.guest_phys_addr + slot0->region.memory_size); - if (kvm_random_seed != last_kvm_seed) { - pr_info("Random seed: 0x%x\n", kvm_random_seed); - last_kvm_seed = kvm_random_seed; - } - kvm_rng = new_kvm_random_state(kvm_random_seed); + if (kvm_random_seed != last_kvm_seed) + kvm_seed_rng(kvm_random_seed); + sync_global_to_guest(vm, kvm_rng); kvm_arch_vm_post_create(vm, nr_runnable_vcpus); @@ -2279,8 +2284,7 @@ void __attribute((constructor)) kvm_selftest_init(void) sigaction(SIGILL, &sig_sa, NULL); sigaction(SIGFPE, &sig_sa, NULL); - kvm_random_seed = last_kvm_seed = random(); - pr_info("Random seed: 0x%x\n", kvm_random_seed); + kvm_seed_rng(random()); kvm_selftest_arch_init(); } -- 2.55.0.rc0.799.gd6f94ed593-goog