linux-kernel - Re: [PATCH 0/3] KVM: support the cpu feature FLUSH

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Message-ID: <CALMp9eTt3xzAEoQ038bJQ9LN0ZOXrSWsN7xnNUD+0SS=WwF7Pg@mail.gmail.com>
Date:   Mon, 20 Mar 2023 09:52:35 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Emanuele Giuseppe Esposito <eesposit@...hat.com>
Cc:     kvm@...r.kernel.org, Ben Serebrin <serebrin@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] KVM: support the cpu feature FLUSH_L1D

On Wed, Feb 1, 2023 at 5:29 AM Emanuele Giuseppe Esposito
<eesposit@...hat.com> wrote:
>
> As the title suggest, if the host cpu supports flush_l1d flag and
> QEMU/userspace wants to boot a VM with the same flag (or emulate same
> host features), KVM should be able to do so.
>
> Patch 3 is the main fix, because if flush_l1d is not advertised by
> KVM, a linux VM will erroneously mark
> /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
> as vulnerable, even though it isn't since the host has the feature
> and takes care of this. Not sure what would happen in the nested case though.
>
> Patch 1 and 2 are just taken and refactored from Jim Mattison's serie that it
> seems was lost a while ago:
> https://patchwork.kernel.org/project/kvm/patch/20180814173049.21756-1-jmattson@google.com/
>
> I thought it was worth re-posting them.

What has changed since the patches were originally posted, and Konrad
dissed them?