linux-kernel - Re: [PATCH v9 05/14] KVM: Allow range-based TLB invalidation from common code

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Date:   Thu, 17 Aug 2023 09:39:31 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Raghavendra Rao Ananta <rananta@...gle.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Fuad Tabba <tabba@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Gavin Shan <gshan@...hat.com>,
        Shaoqin Huang <shahuang@...hat.com>
Subject: Re: [PATCH v9 05/14] KVM: Allow range-based TLB invalidation from common code

On Tue, 15 Aug 2023 23:30:08 +0100,
Sean Christopherson <seanjc@...gle.com> wrote:
> 
> On Fri, Aug 11, 2023, Raghavendra Rao Ananta wrote:
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index ec169f5c7dce2..00f7bda9202f2 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -278,16 +278,14 @@ static inline bool kvm_available_flush_remote_tlbs_range(void)
> >  	return kvm_x86_ops.flush_remote_tlbs_range;
> >  }
> >  
> > -void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
> > -				 gfn_t nr_pages)
> > +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages)
> >  {
> >  	int ret = -EOPNOTSUPP;
> >  
> >  	if (kvm_x86_ops.flush_remote_tlbs_range)
> > -		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, start_gfn,
> > -								   nr_pages);
> > -	if (ret)
> > -		kvm_flush_remote_tlbs(kvm);
> > +		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> > +
> > +	return ret;
> 
> Please write this as
> 
> 	if (kvm_x86_ops.flush_remote_tlbs_range)
> 		return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> 
> 	return -EOPNOTSUPP;
> 
> or alternatively
> 
> 	if (!kvm_x86_ops.flush_remote_tlbs_range)
> 		return -EOPNOTSUPP;
> 
> 	return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> 
> Hmm, I'll throw my official vote for the second version.

I've applied the second version locally.

	M.

-- 
Without deviation from the norm, progress is not possible.