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Message-ID: <8fad453a-09e4-a3ef-81d8-dd791d74a89d@oracle.com>
Date: Mon, 29 Jan 2024 10:42:37 -0800
From: Dongli Zhang <dongli.zhang@...cle.com>
To: kvm@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc: pbonzini@...hat.com, shuah@...nel.org, seanjc@...gle.com,
linux-kernel@...r.kernel.org, joe.jin@...cle.com
Subject: Re: [PATCH 1/1] KVM: selftests: add kvmclock drift test
Ping :)
BTW, I see Vitaly Kuznetsov has a patch to generalize check_clocksource(),
which is also used by this patch.
[PATCH 1/5] KVM: selftests: Generalize check_clocksource() from kvm_clock_test
https://lore.kernel.org/all/20240109141121.1619463-2-vkuznets@redhat.com/
Thank you very much!
Dongli Zhang
On 1/6/24 00:33, Dongli Zhang wrote:
> There is kvmclock drift issue during the vCPU hotplug. It has been fixed by
> the commit c52ffadc65e2 ("KVM: x86: Don't unnecessarily force masterclock
> update on vCPU hotplug").
>
> This is to add the test to verify if the master clock is updated when we
> write 0 to MSR_IA32_TSC from the host side.
>
> Here is the usage example on the KVM with the bugfix reverted.
>
> $ ./kvm_clock_drift -v -p 5
> kvmclock based on old pvclock_vcpu_time_info: 5012221999
> version: 2
> tsc_timestamp: 3277968
> system_time: 11849519
> tsc_to_system_mul: 2152530255
> tsc_shift: 0
> flags: 1
>
> kvmclock based on new pvclock_vcpu_time_info: 5012222411
> version: 4
> tsc_timestamp: 9980576184
> system_time: 5012222411
> tsc_to_system_mul: 2152530255
> tsc_shift: 0
> flags: 1
>
> ==== Test Assertion Failure ====
> x86_64/kvm_clock_drift.c:216: clock_old == clock_new
> pid=14257 tid=14257 errno=4 - Interrupted system call
> 1 0x000000000040277b: main at kvm_clock_drift.c:216
> 2 0x00007f7766fa7e44: ?? ??:0
> 3 0x000000000040286d: _start at ??:?
> kvmclock drift detected, old=5012221999, new=5012222411
>
> Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
> ---
> tools/testing/selftests/kvm/Makefile | 1 +
> .../selftests/kvm/x86_64/kvm_clock_drift.c | 223 ++++++++++++++++++
> 2 files changed, 224 insertions(+)
> create mode 100644 tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 4412b42d95de..c665d0d8d348 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -84,6 +84,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/hyperv_features
> TEST_GEN_PROGS_x86_64 += x86_64/hyperv_ipi
> TEST_GEN_PROGS_x86_64 += x86_64/hyperv_svm_test
> TEST_GEN_PROGS_x86_64 += x86_64/hyperv_tlb_flush
> +TEST_GEN_PROGS_x86_64 += x86_64/kvm_clock_drift
> TEST_GEN_PROGS_x86_64 += x86_64/kvm_clock_test
> TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
> TEST_GEN_PROGS_x86_64 += x86_64/monitor_mwait_test
> diff --git a/tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c b/tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c
> new file mode 100644
> index 000000000000..324f0dbc5762
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/kvm_clock_drift.c
> @@ -0,0 +1,223 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The kvmclock drift test. Emulate vCPU hotplug and online to verify if
> + * there is kvmclock drift.
> + *
> + * Adapted from steal_time.c
> + *
> + * Copyright (C) 2020, Red Hat, Inc.
> + * Copyright (C) 2024 Oracle and/or its affiliates.
> + */
> +
> +#include <asm/kvm_para.h>
> +#include <asm/pvclock.h>
> +#include <asm/pvclock-abi.h>
> +#include <sys/stat.h>
> +
> +#include "kvm_util.h"
> +#include "processor.h"
> +
> +#define NR_VCPUS 2
> +#define NR_SLOTS 2
> +#define KVMCLOCK_SIZE sizeof(struct pvclock_vcpu_time_info)
> +/*
> + * KVMCLOCK_GPA is identity mapped
> + */
> +#define KVMCLOCK_GPA (1 << 30)
> +
> +static uint64_t kvmclock_gpa = KVMCLOCK_GPA;
> +
> +static void guest_code(int cpu)
> +{
> + struct pvclock_vcpu_time_info *kvmclock;
> +
> + /*
> + * vCPU#0 is to detect the change of pvclock_vcpu_time_info
> + */
> + if (cpu == 0) {
> + GUEST_SYNC(0);
> +
> + kvmclock = (struct pvclock_vcpu_time_info *) kvmclock_gpa;
> + wrmsr(MSR_KVM_SYSTEM_TIME_NEW, kvmclock_gpa | KVM_MSR_ENABLED);
> +
> + /*
> + * Backup the pvclock_vcpu_time_info before vCPU#1 hotplug
> + */
> + kvmclock[1] = kvmclock[0];
> +
> + GUEST_SYNC(2);
> + /*
> + * Enter the guest to update pvclock_vcpu_time_info
> + */
> + GUEST_SYNC(4);
> + }
> +
> + /*
> + * vCPU#1 is to emulate the vCPU hotplug
> + */
> + if (cpu == 1) {
> + GUEST_SYNC(1);
> + /*
> + * This is after the host side MSR_IA32_TSC
> + */
> + GUEST_SYNC(3);
> + }
> +}
> +
> +static void run_vcpu(struct kvm_vcpu *vcpu)
> +{
> + struct ucall uc;
> +
> + vcpu_run(vcpu);
> +
> + switch (get_ucall(vcpu, &uc)) {
> + case UCALL_SYNC:
> + case UCALL_DONE:
> + break;
> + case UCALL_ABORT:
> + REPORT_GUEST_ASSERT(uc);
> + default:
> + TEST_ASSERT(false, "Unexpected exit: %s",
> + exit_reason_str(vcpu->run->exit_reason));
> + }
> +}
> +
> +static void kvmclock_dump(struct pvclock_vcpu_time_info *kvmclock)
> +{
> + pr_info(" version: %u\n", kvmclock->version);
> + pr_info(" tsc_timestamp: %lu\n", kvmclock->tsc_timestamp);
> + pr_info(" system_time: %lu\n", kvmclock->system_time);
> + pr_info(" tsc_to_system_mul: %u\n", kvmclock->tsc_to_system_mul);
> + pr_info(" tsc_shift: %d\n", kvmclock->tsc_shift);
> + pr_info(" flags: %u\n", kvmclock->flags);
> + pr_info("\n");
> +}
> +
> +#define CLOCKSOURCE_PATH "/sys/devices/system/clocksource/clocksource0/current_clocksource"
> +
> +static void check_clocksource(void)
> +{
> + char *clk_name;
> + struct stat st;
> + FILE *fp;
> +
> + fp = fopen(CLOCKSOURCE_PATH, "r");
> + if (!fp) {
> + pr_info("failed to open clocksource file: %d; assuming TSC.\n",
> + errno);
> + return;
> + }
> +
> + if (fstat(fileno(fp), &st)) {
> + pr_info("failed to stat clocksource file: %d; assuming TSC.\n",
> + errno);
> + goto out;
> + }
> +
> + clk_name = malloc(st.st_size);
> + TEST_ASSERT(clk_name, "failed to allocate buffer to read file\n");
> +
> + if (!fgets(clk_name, st.st_size, fp)) {
> + pr_info("failed to read clocksource file: %d; assuming TSC.\n",
> + ferror(fp));
> + goto out;
> + }
> +
> + TEST_ASSERT(!strncmp(clk_name, "tsc\n", st.st_size),
> + "clocksource not supported: %s", clk_name);
> +out:
> + fclose(fp);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + struct pvclock_vcpu_time_info *kvmclock;
> + struct kvm_vcpu *vcpus[NR_VCPUS];
> + uint64_t clock_old, clock_new;
> + bool verbose = false;
> + unsigned int gpages;
> + struct kvm_vm *vm;
> + int period = 2;
> + uint64_t tsc;
> + int opt;
> +
> + check_clocksource();
> +
> + while ((opt = getopt(argc, argv, "p:vh")) != -1) {
> + switch (opt) {
> + case 'p':
> + period = atoi_positive("The period (seconds) between vCPU hotplug",
> + optarg);
> + break;
> + case 'v':
> + verbose = true;
> + break;
> + case 'h':
> + default:
> + pr_info("usage: %s [-p period (seconds)] [-v]\n", argv[0]);
> + exit(1);
> + }
> + }
> +
> + vm = vm_create_with_vcpus(NR_VCPUS, guest_code, vcpus);
> + gpages = vm_calc_num_guest_pages(VM_MODE_DEFAULT,
> + KVMCLOCK_SIZE * NR_SLOTS);
> + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
> + KVMCLOCK_GPA, 1, gpages, 0);
> + virt_map(vm, KVMCLOCK_GPA, KVMCLOCK_GPA, gpages);
> +
> + vcpu_args_set(vcpus[0], 1, 0);
> + vcpu_args_set(vcpus[1], 1, 1);
> +
> + /*
> + * Run vCPU#0 and vCPU#1 to update both pvclock_vcpu_time_info and
> + * master clock
> + */
> + run_vcpu(vcpus[0]);
> + run_vcpu(vcpus[1]);
> +
> + /*
> + * Run vCPU#0 to backup the current pvclock_vcpu_time_info
> + */
> + run_vcpu(vcpus[0]);
> +
> + sleep(period);
> +
> + /*
> + * Emulate the hotplug of vCPU#1
> + */
> + vcpu_set_msr(vcpus[1], MSR_IA32_TSC, 0);
> +
> + /*
> + * Emulate the online of vCPU#1
> + */
> + run_vcpu(vcpus[1]);
> +
> + /*
> + * Run vCPU#0 to backup the new pvclock_vcpu_time_info to detect
> + * if there is any change or kvmclock drift
> + */
> + run_vcpu(vcpus[0]);
> +
> + kvmclock = addr_gva2hva(vm, kvmclock_gpa);
> + tsc = kvmclock[0].tsc_timestamp;
> + clock_old = __pvclock_read_cycles(&kvmclock[1], tsc);
> + clock_new = __pvclock_read_cycles(&kvmclock[0], tsc);
> +
> + if (verbose) {
> + pr_info("kvmclock based on old pvclock_vcpu_time_info: %lu\n",
> + clock_old);
> + kvmclock_dump(&kvmclock[1]);
> + pr_info("kvmclock based on new pvclock_vcpu_time_info: %lu\n",
> + clock_new);
> + kvmclock_dump(&kvmclock[0]);
> + }
> +
> + TEST_ASSERT(clock_old == clock_new,
> + "kvmclock drift detected, old=%lu, new=%lu",
> + clock_old, clock_new);
> +
> + kvm_vm_free(vm);
> +
> + return 0;
> +}
>
> base-commit: f2a3fb7234e52f72ff4a38364dbf639cf4c7d6c6
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