linux-kernel - Re: [PATCH v11 055/113] KVM: x86/VMX: introduce vmx tlb_remote_flush and tlb_remote_flush_with

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Date:   Tue, 17 Jan 2023 02:06:43 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v11 055/113] KVM: x86/VMX: introduce vmx tlb_remote_flush
 and tlb_remote_flush_with_range

On Thu, 2023-01-12 at 08:32 -0800, isaku.yamahata@...el.com wrote:
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -244,7 +244,7 @@ static void kvm_flush_remote_tlbs_with_range(struct kvm *kvm,
>  {
>  	int ret = -ENOTSUPP;
>  
> -	if (range && kvm_x86_ops.tlb_remote_flush_with_range)
> +	if (range && kvm_available_flush_tlb_with_range())
>  		ret = static_call(kvm_x86_tlb_remote_flush_with_range)(kvm, range);

Again, IMHO this code change doesn't make code any clearer.  With the new code,
I need to go into the kvm_available_flush_tlb_with_range() to see what's going
on, but with the old code I don't.

That being said, I think kvm_available_flush_tlb_with_range() is sort of
redundant but I can also understand callers don't want to just check whether the
callback is valid.

Btw, I had some memory that I commented this before in some old version
(therefore the 'Again' in my reply), but I failed to dig out -- partially due to
in some old versions (<= v7) I found I have no clue which patch to look at by
just looking at the patch title.