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Date:   Thu, 3 Nov 2022 13:08:02 +0100
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Subject: Re: [PATCH 00/44] KVM: Rework kvm_init() and hardware enabling
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To:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Marc Zyngier <maz@kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
        Anup Patel <anup@brainfault.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Janosch Frank <frankja@linux.ibm.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Eric Farman <farman@linux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>
Cc:     James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Oliver Upton <oliver.upton@linux.dev>,
        Atish Patra <atishp@atishpatra.org>,
        David Hildenbrand <david@redhat.com>, kvm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
        kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org,
        linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Isaku Yamahata <isaku.yamahata@intel.com>,
        Fabiano Rosas <farosas@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Chao Gao <chao.gao@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Yuan Yao <yuan.yao@intel.com>
References: <20221102231911.3107438-1-seanjc@google.com>
From:   Christian Borntraeger <borntraeger@linux.ibm.com>
In-Reply-To: <20221102231911.3107438-1-seanjc@google.com>
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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.