linux-kernel - Re: [PATCH 00/44] KVM: Rework kvm

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Message-ID: <b37267a9-c0b4-9841-71af-d8eab9baeb60@linux.ibm.com>
Date:   Thu, 3 Nov 2022 13:08:02 +0100
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Atish Patra <atishp@...shpatra.org>,
        David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        kvmarm@...ts.cs.columbia.edu, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Fabiano Rosas <farosas@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Chao Gao <chao.gao@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yuan Yao <yuan.yao@...el.com>
Subject: Re: [PATCH 00/44] KVM: Rework kvm_init() and hardware enabling

Am 03.11.22 um 00:18 schrieb Sean Christopherson:
> Non-x86 folks, please test on hardware when possible.  I made a _lot_ of
> mistakes when moving code around.  Thankfully, x86 was the trickiest code
> to deal with, and I'm fairly confident that I found all the bugs I
> introduced via testing.  But the number of mistakes I made and found on
> x86 makes me more than a bit worried that I screwed something up in other
> arch code.
> 
> This is a continuation of Chao's series to do x86 CPU compatibility checks
> during virtualization hardware enabling[1], and of Isaku's series to try
> and clean up the hardware enabling paths so that x86 (Intel specifically)
> can temporarily enable hardware during module initialization without
> causing undue pain for other architectures[2].  It also includes one patch
> from another mini-series from Isaku that provides the less controversial
> patches[3].
> 
> The main theme of this series is to kill off kvm_arch_init(),
> kvm_arch_hardware_(un)setup(), and kvm_arch_check_processor_compat(), which
> all originated in x86 code from way back when, and needlessly complicate
> both common KVM code and architecture code.  E.g. many architectures don't
> mark functions/data as __init/__ro_after_init purely because kvm_init()
> isn't marked __init to support x86's separate vendor modules.
> 
> The idea/hope is that with those hooks gone (moved to arch code), it will
> be easier for x86 (and other architectures) to modify their module init
> sequences as needed without having to fight common KVM code.  E.g. I'm
> hoping that ARM can build on this to simplify its hardware enabling logic,
> especially the pKVM side of things.
> 
> There are bug fixes throughout this series.  They are more scattered than
> I would usually prefer, but getting the sequencing correct was a gigantic
> pain for many of the x86 fixes due to needing to fix common code in order
> for the x86 fix to have any meaning.  And while the bugs are often fatal,
> they aren't all that interesting for most users as they either require a
> malicious admin or broken hardware, i.e. aren't likely to be encountered
> by the vast majority of KVM users.  So unless someone _really_ wants a
> particular fix isolated for backporting, I'm not planning on shuffling
> patches.
> 
> Tested on x86.  Lightly tested on arm64.  Compile tested only on all other
> architectures.

Some sniff tests seem to work ok on s390.