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Re: [PATCH v2] target/i386: always create kvmclock device
From: |
Antoine Damhet |
Subject: |
Re: [PATCH v2] target/i386: always create kvmclock device |
Date: |
Wed, 23 Sep 2020 11:59:43 +0200 |
Hi,
The patch doesn't apply cleanly to master but it works (patched ->
patched working, patched -> unpatched: old behavior, unpatched ->
patched: old behavior)
Thanks to everyone for the swift responses :)
On Tue, Sep 22, 2020 at 05:19:34PM +0200, Vitaly Kuznetsov wrote:
> QEMU's kvmclock device is only created when KVM PV feature bits for
> kvmclock (KVM_FEATURE_CLOCKSOURCE/KVM_FEATURE_CLOCKSOURCE2) are
> exposed to the guest. With 'kvm=off' cpu flag the device is not
> created and we don't call KVM_GET_CLOCK/KVM_SET_CLOCK upon migration.
> It was reported that without these call at least Hyper-V TSC page
> clocksouce (which can be enabled independently) gets broken after
> migration.
>
> Switch to creating kvmclock QEMU device unconditionally, it seems
> to always make sense to call KVM_GET_CLOCK/KVM_SET_CLOCK on migration.
> Use KVM_CAP_ADJUST_CLOCK check instead of CPUID feature bits.
>
> Reported-by: Antoine Damhet <antoine.damhet@blade-group.com>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Tested-by: Antoine Damhet <antoine.damhet@blade-group.com>
> ---
> hw/i386/kvm/clock.c | 7 +++++--
> hw/i386/microvm.c | 2 +-
> hw/i386/pc.c | 1 +
> hw/i386/pc_piix.c | 7 +++++--
> hw/i386/pc_q35.c | 5 ++++-
> include/hw/i386/pc.h | 3 +++
> include/hw/kvm/clock.h | 4 ++--
> target/i386/kvm.c | 5 +++++
> target/i386/kvm_i386.h | 1 +
> 9 files changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
> index 64283358f91d..30cf53393ee1 100644
> --- a/hw/i386/kvm/clock.c
> +++ b/hw/i386/kvm/clock.c
> @@ -328,11 +328,14 @@ static const TypeInfo kvmclock_info = {
> };
>
> /* Note: Must be called after VCPU initialization. */
> -void kvmclock_create(void)
> +void kvmclock_create(bool create_always)
> {
> X86CPU *cpu = X86_CPU(first_cpu);
>
> - if (kvm_enabled() &&
> + if (!kvm_enabled() || !kvm_has_adjust_clock())
> + return;
> +
> + if (create_always ||
> cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) |
> (1ULL << KVM_FEATURE_CLOCKSOURCE2))) {
> sysbus_create_simple(TYPE_KVM_CLOCK, -1, NULL);
> diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
> index 81d0888930d1..fd0b84109154 100644
> --- a/hw/i386/microvm.c
> +++ b/hw/i386/microvm.c
> @@ -119,7 +119,7 @@ static void microvm_devices_init(MicrovmMachineState *mms)
>
> ioapic_init_gsi(gsi_state, "machine");
>
> - kvmclock_create();
> + kvmclock_create(true);
>
> for (i = 0; i < VIRTIO_NUM_TRANSPORTS; i++) {
> sysbus_create_simple("virtio-mmio",
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index d11daacc23cf..0e036ef9c15f 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1956,6 +1956,7 @@ static void pc_machine_class_init(ObjectClass *oc, void
> *data)
> pcmc->acpi_data_size = 0x20000 + 0x8000;
> pcmc->linuxboot_dma_enabled = true;
> pcmc->pvh_enabled = true;
> + pcmc->kvmclock_create_always = true;
> assert(!mc->get_hotplug_handler);
> mc->get_hotplug_handler = pc_get_hotplug_handler;
> mc->hotplug_allowed = pc_hotplug_allowed;
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 32b1453e6a82..1a68338c737b 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -158,8 +158,8 @@ static void pc_init1(MachineState *machine,
>
> x86_cpus_init(x86ms, pcmc->default_cpu_version);
>
> - if (kvm_enabled() && pcmc->kvmclock_enabled) {
> - kvmclock_create();
> + if (pcmc->kvmclock_enabled) {
> + kvmclock_create(pcmc->kvmclock_create_always);
> }
>
> if (pcmc->pci_enabled) {
> @@ -440,11 +440,14 @@ DEFINE_I440FX_MACHINE(v5_2, "pc-i440fx-5.2", NULL,
>
> static void pc_i440fx_5_1_machine_options(MachineClass *m)
> {
> + PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
> +
> pc_i440fx_5_2_machine_options(m);
> m->alias = NULL;
> m->is_default = false;
> compat_props_add(m->compat_props, hw_compat_5_1, hw_compat_5_1_len);
> compat_props_add(m->compat_props, pc_compat_5_1, pc_compat_5_1_len);
> + pcmc->kvmclock_create_always = false;
> }
>
> DEFINE_I440FX_MACHINE(v5_1, "pc-i440fx-5.1", NULL,
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index 0cb9c18cd44d..0dd59bd765b1 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -185,7 +185,7 @@ static void pc_q35_init(MachineState *machine)
>
> x86_cpus_init(x86ms, pcmc->default_cpu_version);
>
> - kvmclock_create();
> + kvmclock_create(pcmc->kvmclock_create_always);
>
> /* pci enabled */
> if (pcmc->pci_enabled) {
> @@ -366,10 +366,13 @@ DEFINE_Q35_MACHINE(v5_2, "pc-q35-5.2", NULL,
>
> static void pc_q35_5_1_machine_options(MachineClass *m)
> {
> + PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
> +
> pc_q35_5_2_machine_options(m);
> m->alias = NULL;
> compat_props_add(m->compat_props, hw_compat_5_1, hw_compat_5_1_len);
> compat_props_add(m->compat_props, pc_compat_5_1, pc_compat_5_1_len);
> + pcmc->kvmclock_create_always = false;
> }
>
> DEFINE_Q35_MACHINE(v5_1, "pc-q35-5.1", NULL,
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index fe52e165b27c..6b22671434b9 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -118,6 +118,9 @@ typedef struct PCMachineClass {
>
> /* use PVH to load kernels that support this feature */
> bool pvh_enabled;
> +
> + /* create kvmclock device even when KVM PV features are not exposed */
> + bool kvmclock_create_always;
> } PCMachineClass;
>
> #define TYPE_PC_MACHINE "generic-pc-machine"
> diff --git a/include/hw/kvm/clock.h b/include/hw/kvm/clock.h
> index 81c66b230207..7994071c4fee 100644
> --- a/include/hw/kvm/clock.h
> +++ b/include/hw/kvm/clock.h
> @@ -15,11 +15,11 @@
>
> #ifdef CONFIG_KVM
>
> -void kvmclock_create(void);
> +void kvmclock_create(bool create_always);
>
> #else /* CONFIG_KVM */
>
> -static inline void kvmclock_create(void)
> +static inline void kvmclock_create(bool create_always)
> {
> }
>
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 4a8b3a41c1bc..20b31b65307b 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -143,6 +143,11 @@ bool kvm_has_adjust_clock_stable(void)
> return (ret == KVM_CLOCK_TSC_STABLE);
> }
>
> +bool kvm_has_adjust_clock(void)
> +{
> + return kvm_check_extension(kvm_state, KVM_CAP_ADJUST_CLOCK);
> +}
> +
> bool kvm_has_exception_payload(void)
> {
> return has_exception_payload;
> diff --git a/target/i386/kvm_i386.h b/target/i386/kvm_i386.h
> index 064b8798a26c..0fce4e51d2d6 100644
> --- a/target/i386/kvm_i386.h
> +++ b/target/i386/kvm_i386.h
> @@ -34,6 +34,7 @@
>
> bool kvm_allows_irq0_override(void);
> bool kvm_has_smm(void);
> +bool kvm_has_adjust_clock(void);
> bool kvm_has_adjust_clock_stable(void);
> bool kvm_has_exception_payload(void);
> void kvm_synchronize_all_tsc(void);
> --
> 2.25.4
>
--
Antoine 'xdbob' Damhet
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