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From: Marcelo Tosatti <mtosatti@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, vkuznets@redhat.com
Subject: Re: [PATCH 1/2] KVM: KVM-on-hyperv: shorten no-entry section on reenlightenment
Date: Wed, 11 Aug 2021 15:03:22 -0300	[thread overview]
Message-ID: <20210811180322.GA178399@fuller.cnet> (raw)
In-Reply-To: <20210811102356.3406687-2-pbonzini@redhat.com>

On Wed, Aug 11, 2021 at 06:23:55AM -0400, Paolo Bonzini wrote:
> During re-enlightenment, update kvmclock a VM at a time instead of
> raising KVM_REQ_MASTERCLOCK_UPDATE for all VMs.  Because the guests
> can now run after TSC emulation has been disabled, invalidate
> their TSC page so that they refer to the reference time counter
> MSR while the update is in progress.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  arch/x86/kvm/x86.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index bab8eb3e0a47..284afaa1db86 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8111,7 +8111,7 @@ static void kvm_hyperv_tsc_notifier(void)
>  
>  	mutex_lock(&kvm_lock);
>  	list_for_each_entry(kvm, &vm_list, vm_list)
> -		kvm_make_mclock_inprogress_request(kvm);
> +		kvm_hv_invalidate_tsc_page(kvm);
>  
>  	hyperv_stop_tsc_emulation();

        hyperv_stop_tsc_emulation();

        /* TSC frequency always matches when on Hyper-V */
        for_each_present_cpu(cpu)
                per_cpu(cpu_tsc_khz, cpu) = tsc_khz;
        kvm_max_guest_tsc_khz = tsc_khz; 

Is this safe with a running guest? Why?


  reply	other threads:[~2021-08-12 13:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-11 10:23 [PATCH 0/2] KVM: x86: abstract locking around pvclock_update_vm_gtod_copy Paolo Bonzini
2021-08-11 10:23 ` [PATCH 1/2] KVM: KVM-on-hyperv: shorten no-entry section on reenlightenment Paolo Bonzini
2021-08-11 18:03   ` Marcelo Tosatti [this message]
2021-08-12 15:53     ` Paolo Bonzini
2021-08-11 10:23 ` [PATCH 2/2] kvm: x86: abstract locking around pvclock_update_vm_gtod_copy Paolo Bonzini

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