linux-kernel - Re: [PATCH v7 00/39] KVM: x86: hyper-v: Fine-grained TLB flush + L2 TLB flush features

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Date:   Tue, 21 Jun 2022 15:00:29 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        Yuan Yao <yuan.yao@...ux.intel.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 00/39] KVM: x86: hyper-v: Fine-grained TLB flush + L2
 TLB flush features

On 6/13/22 15:38, Vitaly Kuznetsov wrote:
> Changes since v6:
> - Rebase to the latest kvm/queue [8baacf67c76c], newly introduced
>    selftests had to be adapted to the overhauled API [blame Sean].
> - Rename 'entry' to 'flush_all_entry' in hv_tlb_flush_enqueue() [Max].
> - Add "KVM: selftests: Rename 'evmcs_test' to 'hyperv_evmcs'" patch.
> - Collect R-b tags.
> 
> Original description:
> 
> Currently, KVM handles HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} requests
> by flushing the whole VPID and this is sub-optimal. This series introduces
> the required mechanism to make handling of these requests more
> fine-grained by flushing individual GVAs only (when requested). On this
> foundation, "Direct Virtual Flush" Hyper-V feature is implemented. The
> feature allows L0 to handle Hyper-V TLB flush hypercalls directly at
> L0 without the need to reflect the exit to L1. This has at least two
> benefits: reflecting vmexit and the consequent vmenter are avoided + L0
> has precise information whether the target vCPU is actually running (and
> thus requires a kick).

I haven't reviewed the selftests part yet, but for the rest I only had 
two very small comments.

Paolo