Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1587468026-15753-1-git-send-email-wanpengli@tencent.com>
 <1587468026-15753-2-git-send-email-wanpengli@tencent.com> <ed968729-5d2a-a318-1d8f-db39e6ee72cb@redhat.com>
 <CANRm+CxzROx=eawemmzh==2Mz-DxKSyYFSxHqLxUiGFFnWkAYw@mail.gmail.com> <d87e0a4b-608a-451b-e3f0-968d46b6cc26@redhat.com>
In-Reply-To: <d87e0a4b-608a-451b-e3f0-968d46b6cc26@redhat.com>
From:   Wanpeng Li <kernellwp@gmail.com>
Date:   Wed, 22 Apr 2020 16:46:12 +0800
Message-ID: <CANRm+CznaiShdq_h1uUnZ_t7k1LX5=cHQwiYOd8632cPnUNHsw@mail.gmail.com>
Subject: Re: [PATCH 1/2] KVM: X86: TSCDEADLINE MSR emulation fastpath
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Haiwei Li <lihaiwei@tencent.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, 22 Apr 2020 at 16:38, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 22/04/20 02:48, Wanpeng Li wrote:
> > On Tue, 21 Apr 2020 at 19:37, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >> On 21/04/20 13:20, Wanpeng Li wrote:
> >>> +     case MSR_IA32_TSCDEADLINE:
> >>> +             if (!kvm_x86_ops.event_needs_reinjection(vcpu)) {
> >>> +                     data = kvm_read_edx_eax(vcpu);
> >>> +                     if (!handle_fastpath_set_tscdeadline(vcpu, data))
> >>> +                             ret = EXIT_FASTPATH_CONT_RUN;
> >>> +             }
> >>>               break;
> >> Can you explain the event_needs_reinjection case?  Also, does this break
> > This is used to catch the case vmexit occurred while another event was
> > being delivered to guest software, I move the
> > vmx_exit_handlers_fastpath() call after vmx_complete_interrupts()
> > which will decode such event and make kvm_event_needs_reinjection
> > return true.
>
> This doesn't need a callback, kvm_event_needs_reinjection should be enough.
>
> You should also check other conditions such as
>
>         vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu)
>             || need_resched() || signal_pending(current)
>
> before doing CONT_RUN.

Agreed.

>
> >> AMD which does not implement the callback?
> > Now I add the tscdeadline msr emulation and vmx-preemption timer
> > fastpath pair for Intel platform.
>
> But this would cause a crash if you run on AMD.

Yes. :)

    Wanpeng