linux-kernel - Re: [PATCH v8 02/14] KVM: Declare kvm_arch_flush_remote

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Date:   Thu, 10 Aug 2023 20:26:09 +0800
From:   Shaoqin Huang <shahuang@...hat.com>
To:     Raghavendra Rao Ananta <rananta@...gle.com>,
        Gavin Shan <gshan@...hat.com>
Cc:     Oliver Upton <oliver.upton@...ux.dev>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.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
Subject: Re: [PATCH v8 02/14] KVM: Declare kvm_arch_flush_remote_tlbs()
 globally



On 8/10/23 00:38, Raghavendra Rao Ananta wrote:
> Hi Gavin,
> 
> On Tue, Aug 8, 2023 at 9:00 PM Gavin Shan <gshan@...hat.com> wrote:
>>
>>
>> On 8/9/23 09:13, Raghavendra Rao Ananta wrote:
>>> There's no reason for the architectures to declare
>>> kvm_arch_flush_remote_tlbs() in their own headers. Hence to
>>> avoid this duplication, make the declaration global, leaving
>>> the architectures to define only __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS
>>> as needed.
>>>
>>> Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
>>> ---
>>>    arch/mips/include/asm/kvm_host.h | 1 -
>>>    include/linux/kvm_host.h         | 2 ++
>>>    2 files changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
>>> index 9b0ad8f3bf327..54a85f1d4f2c8 100644
>>> --- a/arch/mips/include/asm/kvm_host.h
>>> +++ b/arch/mips/include/asm/kvm_host.h
>>> @@ -897,6 +897,5 @@ static inline void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu) {}
>>>    static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
>>>
>>>    #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS
>>> -int kvm_arch_flush_remote_tlbs(struct kvm *kvm);
>>>
>>>    #endif /* __MIPS_KVM_HOST_H__ */
>>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>>> index e3f968b38ae97..ade5d4500c2ce 100644
>>> --- a/include/linux/kvm_host.h
>>> +++ b/include/linux/kvm_host.h
>>> @@ -1484,6 +1484,8 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
>>>    {
>>>        return -ENOTSUPP;
>>>    }
>>> +#else
>>> +int kvm_arch_flush_remote_tlbs(struct kvm *kvm);
>>>    #endif
>>>
>>>    #ifdef __KVM_HAVE_ARCH_NONCOHERENT_DMA
>>
>> Is the declaration inconsistent to that in arch/x86/include/asm/kvm_host.h?
>> In order to keep them consistent, I guess we need move kvm_arch_flush_remote_tlbs()
>> from x86's header file to arch/x86/kvm/mmu/mmu.c and 'inline' needs to be dropped.
>>
> Unsure of the original intentions, I didn't want to disturb any
> existing arrangements. If more people agree to this refactoring, I'm
> happy to move.

This is amazing to me. This change can be compiled without any error 
even if the declaration inconsistent between the kvm_host.h and x86's 
header file.

I'm curious which option make it possible?

Thanks,
Shaoqin

> 
> Thank you.
> Raghavendra
>> Thanks,
>> Gavin
>>
> 

-- 
Shaoqin