linux-kernel - Re: [PATCH v12 11/84] KVM: Rename gfn_to_page_many_atomic() to kvm_prefetch

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Message-ID: <87frrncgzv.fsf@draig.linaro.org>
Date: Fri, 02 Aug 2024 12:16:04 +0100
From: Alex Bennée <alex.bennee@...aro.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,  Marc Zyngier <maz@...nel.org>,
  Oliver Upton <oliver.upton@...ux.dev>,  Tianrui Zhao
 <zhaotianrui@...ngson.cn>,  Bibo Mao <maobibo@...ngson.cn>,  Huacai Chen
 <chenhuacai@...nel.org>,  Michael Ellerman <mpe@...erman.id.au>,  Anup
 Patel <anup@...infault.org>,  Paul Walmsley <paul.walmsley@...ive.com>,
  Palmer Dabbelt <palmer@...belt.com>,  Albert Ou <aou@...s.berkeley.edu>,
  Christian Borntraeger <borntraeger@...ux.ibm.com>,  Janosch Frank
 <frankja@...ux.ibm.com>,  Claudio Imbrenda <imbrenda@...ux.ibm.com>,
  kvm@...r.kernel.org,  linux-arm-kernel@...ts.infradead.org,
  kvmarm@...ts.linux.dev,  loongarch@...ts.linux.dev,
  linux-mips@...r.kernel.org,  linuxppc-dev@...ts.ozlabs.org,
  kvm-riscv@...ts.infradead.org,  linux-riscv@...ts.infradead.org,
  linux-kernel@...r.kernel.org,  David Matlack <dmatlack@...gle.com>,
  David Stevens <stevensd@...omium.org>
Subject: Re: [PATCH v12 11/84] KVM: Rename gfn_to_page_many_atomic() to
 kvm_prefetch_pages()

Sean Christopherson <seanjc@...gle.com> writes:

> Rename gfn_to_page_many_atomic() to kvm_prefetch_pages() to try and
> communicate its true purpose, as the "atomic" aspect is essentially a
> side effect of the fact that x86 uses the API while holding mmu_lock.

It's never too late to start adding some kdoc annotations to a function
and renaming a kvm_host API call seems like a good time to do it.

> E.g. even if mmu_lock weren't held, KVM wouldn't want to fault-in pages,
> as the goal is to opportunistically grab surrounding pages that have
> already been accessed and/or dirtied by the host, and to do so quickly.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
<snip>

/**
 * kvm_prefetch_pages() - opportunistically grab previously accessed pages
 * @slot: which @kvm_memory_slot the pages are in
 * @gfn: guest frame
 * @pages: array to receives page pointers
 * @nr_pages: number of pages
 *
 * Returns the number of pages actually mapped.
 */

?

>  
> -int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
> -			    struct page **pages, int nr_pages)
> +int kvm_prefetch_pages(struct kvm_memory_slot *slot, gfn_t gfn,
> +		       struct page **pages, int nr_pages)
>  {
>  	unsigned long addr;
>  	gfn_t entry = 0;
> @@ -3075,7 +3075,7 @@ int gfn_to_page_many_atomic(struct kvm_memory_slot *slot, gfn_t gfn,
>  
>  	return get_user_pages_fast_only(addr, nr_pages, FOLL_WRITE, pages);
>  }
> -EXPORT_SYMBOL_GPL(gfn_to_page_many_atomic);
> +EXPORT_SYMBOL_GPL(kvm_prefetch_pages);
>  
>  /*
>   * Do not use this helper unless you are absolutely certain the gfn _must_ be

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro