linux-kernel - Re: [PATCH v3 10/25] KVM: x86/mmu: Drop the return code from kvm_x86_ops.remove_external

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Message-ID: <aPiZ2DEQ6qW5r5rY@yzhao56-desk.sh.intel.com>
Date: Wed, 22 Oct 2025 16:46:16 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: 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>, Madhavan Srinivasan
	<maddy@...ux.ibm.com>, Anup Patel <anup@...infault.org>, Paul Walmsley
	<pjw@...nel.org>, 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>, Paolo Bonzini <pbonzini@...hat.com>, "Kirill A.
 Shutemov" <kas@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<kvmarm@...ts.linux.dev>, <kvm@...r.kernel.org>, <loongarch@...ts.linux.dev>,
	<linux-mips@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<kvm-riscv@...ts.infradead.org>, <linux-riscv@...ts.infradead.org>,
	<x86@...nel.org>, <linux-coco@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, Ira Weiny <ira.weiny@...el.com>, Kai Huang
	<kai.huang@...el.com>, Michael Roth <michael.roth@....com>, Vishal Annapurve
	<vannapurve@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Ackerley Tng <ackerleytng@...gle.com>, Binbin Wu <binbin.wu@...ux.intel.com>
Subject: Re: [PATCH v3 10/25] KVM: x86/mmu: Drop the return code from
 kvm_x86_ops.remove_external_spte()

On Thu, Oct 16, 2025 at 05:32:28PM -0700, Sean Christopherson wrote:
> Opportunistically pass the spte instead of the pfn, as the API is clearly
> about removing an spte.
>From my perspective, "remove_external_spte" means removing an external SPTE (not
a mirror SPTE). So passing in pfn_for_gfn seems reasonable as well.

Additionally, passing in the pfn eliminates potential concerns about incorrect
spte content.

> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 48598d017d6f..7e92aebd07e8 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1855,8 +1855,8 @@ struct kvm_x86_ops {
>  				 void *external_spt);
>  
>  	/* Update external page table from spte getting removed, and flush TLB. */
> -	int (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
> -				    kvm_pfn_t pfn_for_gfn);
> +	void (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
> +				     u64 spte);
Also update set_external_spte?

        /* Update the external page table from spte getting set. */                
        int (*set_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
                                 kvm_pfn_t pfn_for_gfn);