linux-kernel - Re: [PATCH 6/6] KVM: VMX: enable IPI virtualization

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: <0d6f7852-95b3-d628-955b-f44d88a86478@redhat.com>
Date:   Sun, 18 Jul 2021 22:32:38 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Zeng Guang <guang.zeng@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kim Phillips <kim.phillips@....com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        Kai Huang <kai.huang@...el.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Robert Hu <robert.hu@...el.com>, Gao Chao <chao.gao@...el.com>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>
Subject: Re: [PATCH 6/6] KVM: VMX: enable IPI virtualization

On 17/07/21 05:55, Zeng Guang wrote:
>>>      if (_cpu_based_exec_control & 
>>> CPU_BASED_ACTIVATE_TERTIARY_CONTROLS) {
>>> -        u64 opt3 = 0;
>>> +        u64 opt3 = enable_ipiv ? TERTIARY_EXEC_IPI_VIRT : 0;
>>>          u64 min3 = 0;
>>
>> I like the idea of changing opt3, but it's different from how 
>> setup_vmcs_config works for the other execution controls.  Let me 
>> think if it makes sense to clean this up, and move the handling of 
>> other module parameters from hardware_setup() to setup_vmcs_config().
>>
> May be an exception for ipiv feature ?

Yes, possibly.  I'll look into using this idea for other parameters.

>>> +    if (vmx->ipiv_active)
>>> +        install_pid(vmx);
>>
>> This should be if (enable_ipiv) instead, I think.
>>
>> In fact, in all other places that are using vmx->ipiv_active, you can 
>> actually replace it with enable_ipiv; they are all reached only with 
>> kvm_vcpu_apicv_active(vcpu) == true.
>>
> enable_ipiv as a global variable indicates the hardware capability to 
> enable IPIv. Each VM may have different IPIv configuration according to 
> kvm_vcpu_apicv_active status. So we use ipiv_active per VM to enclose 
> IPIv related operations.

Understood, but in practice all uses of vmx->ipiv_active are guarded by 
kvm_vcpu_apicv_active so they are always reached with vmx->ipiv_active 
== enable_ipiv.

The one above instead seems wrong and should just use enable_ipiv.

Paolo