linux-kernel - Re: [PATCH v9 0/9] IPI virtualization support for VM

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] [day] [month] [year] [list]

Message-ID: <2d33b71a-13e5-d377-abc2-c20958526497@redhat.com>
Date:   Mon, 2 May 2022 18:18:39 +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>
Subject: Re: [PATCH v9 0/9] IPI virtualization support for VM

On 4/19/22 17:31, Zeng Guang wrote:
> Currently, issuing an IPI except self-ipi in guest on Intel CPU
> always causes a VM-exit. It can lead to non-negligible overhead
> to some workloads involving frequent IPIs when running in VMs.
> 
> IPI virtualization is a new VT-x feature, targeting to eliminate
> VM-exits on source vCPUs when issuing unicast, physical-addressing
> IPIs. Once it is enabled, the processor virtualizes following kinds
> of operations that send IPIs without causing VM-exits:
> - Memory-mapped ICR writes
> - MSR-mapped ICR writes
> - SENDUIPI execution
> 
> This patch series implements IPI virtualization support in KVM.
> 
> Patches 1-4 add tertiary processor-based VM-execution support
> framework, which is used to enumerate IPI virtualization.
> 
> Patch 5 handles APIC-write VM exit due to writes to ICR MSR when
> guest works in x2APIC mode. This is a new case introduced by
> Intel VT-x.
> 
> Patch 6 cleanup code in vmx_refresh_apicv_exec_ctrl(). Prepare for
> IPIv status dynamical update along with APICv status change.
> 
> Patch 7 move kvm_arch_vcpu_precreate() under kvm->lock protection.
> This patch is prepared for IPIv PID-table allocation prior to
> the creation of vCPUs.
> 
> Patch 8 provide userspace capability to set maximum possible VCPU
> ID for current VM. IPIv can refer to this value to allocate memory
> for PID-pointer table.
> 
> Patch 9 implements IPI virtualization related function including
> feature enabling through tertiary processor-based VM-execution in
> various scenarios of VMCS configuration, PID table setup in vCPU
> creation and vCPU block consideration.

I queued it, but I am not going to send it to Linus until I get 
selftests for KVM_CAP_MAX_VCPU_ID.  Selftests are generally _not_ 
optional for new userspace API.

Please send a patch on top of kvm/queue.

Paolo