linux-kernel - Re: [PATCH] kvm: x86/mmu: Simplify pte_list

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Message-ID: <167934153606.1941128.1026865175616779306.b4-ty@google.com>
Date:   Thu, 23 Mar 2023 15:50:30 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org,
        Lai Jiangshan <jiangshanlai@...il.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org
Subject: Re: [PATCH] kvm: x86/mmu: Simplify pte_list_{add|remove}

On Fri, 13 Jan 2023 20:29:10 +0800, Lai Jiangshan wrote:
> Simplify pte_list_{add|remove} by ensuring all the non-head pte_list_desc
> to be full and addition/removal actions being performed on the head.
> 
> To make pte_list_add() return a count as before, @tail_count is also
> added to the struct pte_list_desc.
> 
> No visible performace is changed in tests.  But pte_list_add() is no longer
> shown in the perf result for the COWed pages even the guest forks millions
> of tasks.
> 
> [...]

Applied to kvm-x86 mmu, thanks!  I added quite a few comments and a BUG_ON() to
sanity check that the head is never empty when trying to remove an entry, but I
didn't make anything changes to the code itself.

[1/1] kvm: x86/mmu: Simplify pte_list_{add|remove}
      https://github.com/kvm-x86/linux/commit/141705b78381

--
https://github.com/kvm-x86/linux/tree/next
https://github.com/kvm-x86/linux/tree/fixes