linux-kernel - Re: [PATCH v3 0/2] KVM: x86: hyper-v: Fix TSC page update after KVM_SET

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Message-ID: <dd1b6f3e-273a-8162-9937-428ae2237254@redhat.com>
Date:   Wed, 31 Mar 2021 17:08:40 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/2] KVM: x86: hyper-v: Fix TSC page update after
 KVM_SET_CLOCK(0) call

On 31/03/21 14:41, Vitaly Kuznetsov wrote:
> Changes since v2:
> - Fix the issue by using master_kernel_ns/get_kvmclock_base_ns() instead of
>   get_kvmclock_ns() when handling KVM_SET_CLOCK.
> - Rebase on Paolo's "KVM: x86: fix lockdep splat due to Xen runstate
>   update" series and use spin_lock_irq()/spin_unlock_irq() [Paolo]
> 
> Original description:
> 
> I discovered that after KVM_SET_CLOCK(0) TSC page value in the guest can
> go through the roof and apparently we have a signedness issue when the
> update is performed. Fix the issue and add a selftest.
> 
> Vitaly Kuznetsov (2):
>    KVM: x86: Prevent 'hv_clock->system_time' from going negative in
>      kvm_guest_time_update()
>    selftests: kvm: Check that TSC page value is small after
>      KVM_SET_CLOCK(0)
> 
>   arch/x86/kvm/x86.c                            | 19 +++++++++++++++++--
>   .../selftests/kvm/x86_64/hyperv_clock.c       | 13 +++++++++++--
>   2 files changed, 28 insertions(+), 4 deletions(-)
> 

Queued, thanks.

Paolo