linux-kernel - Re: [PATCH 1/2] KVM: X86: TSCDEADLINE MSR emulation fastpath

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d87e0a4b-608a-451b-e3f0-968d46b6cc26@redhat.com>
Date:   Wed, 22 Apr 2020 10:38:39 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Haiwei Li <lihaiwei@...cent.com>
Subject: Re: [PATCH 1/2] KVM: X86: TSCDEADLINE MSR emulation fastpath

On 22/04/20 02:48, Wanpeng Li wrote:
> On Tue, 21 Apr 2020 at 19:37, Paolo Bonzini <pbonzini@...hat.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.

>> 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.

Paolo