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Tue, 10 Oct 2023 09:13:12 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGs2fH4NHjpkUxflX5p7dSmGCMRr2l+ZvyM5EgqLstCWYTU6mdw3EFtRmwc7jHyDGY6IYO9kg== X-Received: by 2002:a05:600c:ad0:b0:405:375d:b860 with SMTP id c16-20020a05600c0ad000b00405375db860mr17819250wmr.21.1696954392437; Tue, 10 Oct 2023 09:13:12 -0700 (PDT) Received: from starship ([89.237.100.246]) by smtp.gmail.com with ESMTPSA id m10-20020a7bce0a000000b00405953973c3sm16790678wmc.6.2023.10.10.09.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Oct 2023 09:13:11 -0700 (PDT) Message-ID: <7c2a77bb3ec9f85f684218eb80654adcdfefd60d.camel@redhat.com> Subject: Re: [PATCH 1/1] selftests: KVM: add test to print boottime wallclock From: Maxim Levitsky To: Dongli Zhang , kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org, pbonzini@redhat.com, shuah@kernel.org, seanjc@google.com, dwmw2@infradead.org, joe.jin@oracle.com Date: Tue, 10 Oct 2023 19:13:10 +0300 In-Reply-To: <20231006175715.105517-1-dongli.zhang@oracle.com> References: <20231006175715.105517-1-dongli.zhang@oracle.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org У пт, 2023-10-06 у 10:57 -0700, Dongli Zhang пише: > As inspired by the discussion in [1], the boottime wallclock may drift due > to the fact that the masterclock (or host monotonic clock) and kvmclock are > calculated based on the algorithms in different domains. > > This is to introduce a testcase to print the boottime wallclock > periodically to help diagnose the wallclock drift issue in the future. > > The idea is to wrmsr the MSR_KVM_WALL_CLOCK_NEW, and read the boottime > wallclock nanoseconds immediately. > > References: > [1] https://lore.kernel.org/all/20231001111313.77586-1-nsaenz@amazon.com > > Cc: David Woodhouse > Signed-off-by: Dongli Zhang > --- > tools/testing/selftests/kvm/Makefile | 3 +- > .../selftests/kvm/x86_64/boottime_wallclock.c | 100 ++++++++++++++++++ > 2 files changed, 102 insertions(+), 1 deletion(-) > create mode 100644 tools/testing/selftests/kvm/x86_64/boottime_wallclock.c > > diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile > index a3bb36fb3cfc..fea05b0118de 100644 > --- a/tools/testing/selftests/kvm/Makefile > +++ b/tools/testing/selftests/kvm/Makefile > @@ -60,7 +60,8 @@ LIBKVM_riscv += lib/riscv/ucall.c > TEST_PROGS_x86_64 += x86_64/nx_huge_pages_test.sh > > # Compiled test targets > -TEST_GEN_PROGS_x86_64 = x86_64/cpuid_test > +TEST_GEN_PROGS_x86_64 = x86_64/boottime_wallclock > +TEST_GEN_PROGS_x86_64 += x86_64/cpuid_test > TEST_GEN_PROGS_x86_64 += x86_64/cr4_cpuid_sync_test > TEST_GEN_PROGS_x86_64 += x86_64/dirty_log_page_splitting_test > TEST_GEN_PROGS_x86_64 += x86_64/get_msr_index_features > diff --git a/tools/testing/selftests/kvm/x86_64/boottime_wallclock.c b/tools/testing/selftests/kvm/x86_64/boottime_wallclock.c > new file mode 100644 > index 000000000000..cc48c9b19920 > --- /dev/null > +++ b/tools/testing/selftests/kvm/x86_64/boottime_wallclock.c > @@ -0,0 +1,100 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (C) 2023 Oracle and/or its affiliates. > + */ > + > +#include > +#include > + > +#include "kvm_util.h" > +#include "processor.h" > + > +static int period = 10; > + > +#define GUEST_SYNC_WALLCLOCK(__stage, __val) \ > + GUEST_SYNC_ARGS(__stage, __val, 0, 0, 0) > + > +static void guest_main(vm_paddr_t wc_pa, struct pvclock_wall_clock *wc) > +{ > + uint64_t wallclock; > + > + while (true) { > + wrmsr(MSR_KVM_WALL_CLOCK_NEW, wc_pa); > + > + wallclock = wc->sec * NSEC_PER_SEC + wc->nsec; > + > + GUEST_SYNC_WALLCLOCK(0, wallclock); Won't this fill the output very fast? Do you think it will be worth it to wait some time (e.g 1 second or at least 1/10 of a second) between each print? > + } > +} > + > +static void handle_sync(struct ucall *uc) > +{ > + uint64_t wallclock; > + > + wallclock = uc->args[2]; > + > + pr_info("Boottime wallclock value: %"PRIu64" ns\n", wallclock); > +} > + > +static void handle_abort(struct ucall *uc) > +{ > + REPORT_GUEST_ASSERT(*uc); > +} > + > +static void enter_guest(struct kvm_vcpu *vcpu) > +{ > + struct ucall uc; > + > + while (true) { > + vcpu_run(vcpu); > + > + TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO); > + > + switch (get_ucall(vcpu, &uc)) { > + case UCALL_SYNC: > + handle_sync(&uc); > + break; > + case UCALL_ABORT: > + handle_abort(&uc); > + return; > + default: > + TEST_ASSERT(0, "unhandled ucall: %ld\n", uc.cmd); > + return; > + } > + > + sleep(period); > + } > +} > + > +int main(int argc, char *argv[]) > +{ > + struct kvm_vcpu *vcpu; > + struct kvm_vm *vm; > + vm_vaddr_t wc_gva; > + vm_paddr_t wc_gpa; > + int opt; > + > + while ((opt = getopt(argc, argv, "p:h")) != -1) { > + switch (opt) { > + case 'p': > + period = atoi_positive("The period (seconds)", optarg); > + break; > + case 'h': > + default: > + pr_info("usage: %s [-p period (seconds)]\n", argv[0]); > + exit(1); > + } > + } > + > + pr_info("Capture boottime wallclock every %d seconds.\n", period); > + pr_info("Stop with Ctrl + c.\n\n"); > + > + vm = vm_create_with_one_vcpu(&vcpu, guest_main); > + > + wc_gva = vm_vaddr_alloc(vm, getpagesize(), 0x10000); > + wc_gpa = addr_gva2gpa(vm, wc_gva); > + vcpu_args_set(vcpu, 2, wc_gpa, wc_gva); > + > + enter_guest(vcpu); > + kvm_vm_free(vm); > +} Best regards, Maxim Levitsky