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Date:   Thu, 3 Nov 2022 22:34:10 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Isaku Yamahata <isaku.yamahata@gmail.com>
Cc:     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>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        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>,
        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,
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        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>
Subject: Re: [PATCH 36/44] KVM: x86: Do compatibility checks when onlining CPU
Message-ID: <Y2RB4qT02EkhMjPL@google.com>
References: <20221102231911.3107438-1-seanjc@google.com>
 <20221102231911.3107438-37-seanjc@google.com>
 <20221103210402.GB1063309@ls.amr.corp.intel.com>
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On Thu, Nov 03, 2022, Isaku Yamahata wrote:
> On Wed, Nov 02, 2022 at 11:19:03PM +0000,
> Sean Christopherson <seanjc@google.com> wrote:
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index f223c845ed6e..c99222b71fcc 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1666,7 +1666,7 @@ struct kvm_x86_nested_ops {
> >  };
> >  
> >  struct kvm_x86_init_ops {
> > -	int (*check_processor_compatibility)(void);
> > +	int (*check_processor_compatibility)(int cpu);
> 
> Is this cpu argument used only for error message to include cpu number
> with avoiding repeating raw_smp_processor_id() in pr_err()?

Yep.

> The actual check is done on the current executing cpu.
> 
> If cpu != raw_smp_processor_id(), cpu is wrong. Although the function is called
> in non-preemptive context, it's a bit confusing. So voting to remove it and
> to use.

What if I rename the param is this_cpu?  I 100% agree the argument is confusing
as-is, but forcing all the helpers to manually grab the cpu is quite annoying.