linux-kernel - Re: [PATCH mm-unstable v2 09/10] kvm/x86: add kvm_arch_test_clear

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Message-ID: <f0fc6e43-ffe3-dc38-03c1-77b2105cd0fb@redhat.com>
Date:   Fri, 9 Jun 2023 11:06:02 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yu Zhao <yuzhao@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alistair Popple <apopple@...dia.com>,
        Anup Patel <anup@...infault.org>,
        Ben Gardon <bgardon@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fabiano Rosas <farosas@...ux.ibm.com>,
        Gaosheng Cui <cuigaosheng1@...wei.com>,
        Gavin Shan <gshan@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jonathan Corbet <corbet@....net>,
        Marc Zyngier <maz@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Larabel <michael@...haellarabel.com>,
        Mike Rapoport <rppt@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Paul Mackerras <paulus@...abs.org>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thomas Huth <thuth@...hat.com>, Will Deacon <will@...nel.org>,
        Zenghui Yu <yuzenghui@...wei.com>, kvmarm@...ts.linux.dev,
        kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-trace-kernel@...r.kernel.org, x86@...nel.org,
        linux-mm@...gle.com
Subject: Re: [PATCH mm-unstable v2 09/10] kvm/x86: add
 kvm_arch_test_clear_young()

On 5/27/23 01:44, Yu Zhao wrote:
> +#define kvm_arch_has_test_clear_young kvm_arch_has_test_clear_young
> +static inline bool kvm_arch_has_test_clear_young(void)
> +{
> +	return IS_ENABLED(CONFIG_X86_64) &&
> +	       (!IS_REACHABLE(CONFIG_KVM) || (tdp_mmu_enabled && shadow_accessed_mask));
> +}

I don't think you need IS_REACHABLE(CONFIG_KVM) here, it would be a bug 
if this is called from outside KVM code.

Maybe make it a BUILD_BUG_ON?

Paolo