linux-kernel - Re: [RFC PATCH v2 12/23] KVM: x86/mmu: Introduce kvm_split_cross_boundary

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Message-ID: <aR1kRmOrSK0Jrp3I@yzhao56-desk.sh.intel.com>
Date: Wed, 19 Nov 2025 14:31:34 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: <pbonzini@...hat.com>, <seanjc@...gle.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>, <x86@...nel.org>,
	<rick.p.edgecombe@...el.com>, <dave.hansen@...el.com>, <kas@...nel.org>,
	<tabba@...gle.com>, <ackerleytng@...gle.com>, <michael.roth@....com>,
	<david@...hat.com>, <vannapurve@...gle.com>, <vbabka@...e.cz>,
	<thomas.lendacky@....com>, <pgonda@...gle.com>, <fan.du@...el.com>,
	<jun.miao@...el.com>, <ira.weiny@...el.com>, <isaku.yamahata@...el.com>,
	<xiaoyao.li@...el.com>, <binbin.wu@...ux.intel.com>, <chao.p.peng@...el.com>
Subject: Re: [RFC PATCH v2 12/23] KVM: x86/mmu: Introduce
 kvm_split_cross_boundary_leafs()

On Thu, Aug 07, 2025 at 05:43:58PM +0800, Yan Zhao wrote:
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 9182192daa3a..13910ae05f76 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -1647,6 +1647,33 @@ static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm,
>  				 start, end - 1, can_yield, true, flush);
>  }
>  
> +/*
> + * Split large leafs crossing the boundary of the specified range
> + *
> + * Return value:
> + * 0 : success, no flush is required;
> + * 1 : success, flush is required;
> + * <0: failure.
> + */
> +int kvm_split_cross_boundary_leafs(struct kvm *kvm, struct kvm_gfn_range *range,
> +				   bool shared)
> +{
> +	bool ret = 0;
> +
> +	lockdep_assert_once(kvm->mmu_invalidate_in_progress ||
> +			    lockdep_is_held(&kvm->slots_lock) ||
> +			    srcu_read_lock_held(&kvm->srcu));
> +
> +	if (!range->may_block)
> +		return -EOPNOTSUPP;
> +
> +	if (tdp_mmu_enabled)
> +		ret = kvm_tdp_mmu_gfn_range_split_cross_boundary_leafs(kvm, range, shared);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(kvm_split_cross_boundary_leafs);
  
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index fb79d2b7decd..6137b76341e1 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -273,6 +273,8 @@ struct kvm_gfn_range {
>  bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
>  bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
>  bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range);
> +int kvm_split_cross_boundary_leafs(struct kvm *kvm, struct kvm_gfn_range *range,
> +				   bool shared);
Note to myself: Provide a default implementation for non-x86 platforms.