Re: [PATCHv2 2/2] kvm: x86: implement KVM PM-notifier

Marc Zyngier
2021-06-05T09:00:22Z

On Sat, 05 Jun 2021 03:30:42 +0100,
Sergey Senozhatsky <senozhatsky@chromium.org> wrote:
>
> Implement PM hibernation/suspend prepare notifiers so that KVM
> can reliably set PVCLOCK_GUEST_STOPPED on VCPUs and properly
> suspend VMs.
>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
> arch/x86/kvm/Kconfig | 1 +
> arch/x86/kvm/x86.c | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 34 insertions(+)
>
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index fb8efb387aff..f8e6689f490b 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -43,6 +43,7 @@ config KVM
> select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> select KVM_VFIO
> select SRCU
> + select HAVE_KVM_PM_NOTIFIER

if you write this as:

select HAVE_KVM_PM_NOTIFIER if PM

...

> help
> Support hosting fully virtualized guest machines using hardware
> virtualization extensions. You will need a fairly recent
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b594275d49b5..533d3d010a21 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -58,6 +58,7 @@
> #include <linux/sched/isolation.h>
> #include <linux/mem_encrypt.h>
> #include <linux/entry-kvm.h>
> +#include <linux/suspend.h>
>
> #include <trace/events/kvm.h>
>
> @@ -5615,6 +5616,38 @@ static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm, void __user *argp)
> return 0;
> }
>
> +#if defined(CONFIG_PM) && defined(CONFIG_HAVE_KVM_PM_NOTIFIER)

... you can simplify this expression to be a simple

#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER

in both patches.

> +static int kvm_arch_suspend_notifier(struct kvm *kvm)
> +{
> + struct kvm_vcpu *vcpu;
> + int i, ret;
> +
> + mutex_lock(&kvm->lock);
> + kvm_for_each_vcpu(i, vcpu, kvm) {
> + ret = kvm_set_guest_paused(vcpu);
> + if (ret) {
> + pr_err("Failed to pause guest VCPU%d: %d\n",
> + vcpu->vcpu_id, ret);

Is it really a good idea to fail suspend when a guest doesn't have PV
time enabled? I also wonder how useful the pr_err() is, given that it
contains no information that would help identifying which guest failed
to pause.

> + break;
> + }
> + }
> + mutex_unlock(&kvm->lock);
> +
> + return ret ? NOTIFY_BAD : NOTIFY_DONE;
> +}
> +
> +int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long state)
> +{
> + switch (state) {
> + case PM_HIBERNATION_PREPARE:
> + case PM_SUSPEND_PREPARE:
> + return kvm_arch_suspend_notifier(kvm);
> + }
> +
> + return NOTIFY_DONE;
> +}
> +#endif /* CONFIG_PM && CONFIG_HAVE_KVM_PM_NOTIFIER */
> +
> long kvm_arch_vm_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg)
> {
> --
> 2.32.0.rc1.229.g3e70b5a671-goog
>
>

Thanks,

M.

--
Without deviation from the norm, progress is not possible.