linux-kernel - Re: [RFC PATCH 19/21] KVM: gmem: Split huge boundary leafs for punch hole of private memory

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Message-ID: <a850503bc9bd789d2531fa64c5321d2d9cce5725.camel@gmail.com>
Date: Thu, 24 Apr 2025 12:19:32 +0200
From: Francesco Lavra <francescolavra.fl@...il.com>
To: yan.y.zhao@...el.com
Cc: ackerleytng@...gle.com, binbin.wu@...ux.intel.com,
 chao.p.peng@...el.com,  dave.hansen@...el.com, david@...hat.com,
 fan.du@...el.com, ira.weiny@...el.com,  isaku.yamahata@...el.com,
 jroedel@...e.de, jun.miao@...el.com,  kirill.shutemov@...el.com,
 kvm@...r.kernel.org, linux-kernel@...r.kernel.org,  michael.roth@....com,
 pbonzini@...hat.com, pgonda@...gle.com,  quic_eberman@...cinc.com,
 rick.p.edgecombe@...el.com, seanjc@...gle.com,  tabba@...gle.com,
 thomas.lendacky@....com, vannapurve@...gle.com, vbabka@...e.cz, 
 x86@...nel.org, xiaoyao.li@...el.com, zhiquan1.li@...el.com
Subject: Re: [RFC PATCH 19/21] KVM: gmem: Split huge boundary leafs for
 punch hole of private memory

On 2025-04-24 at 3:08, Yan Zhao wrote:
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 4bb140e7f30d..008061734ac5 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -292,13 +292,14 @@ static struct folio *kvm_gmem_get_folio(struct
> inode *inode, pgoff_t index, int
>  	return folio;
>  }
>  
> -static void kvm_gmem_invalidate_begin(struct kvm_gmem *gmem, pgoff_t
> start,
> -				      pgoff_t end)
> +static int kvm_gmem_invalidate_begin(struct kvm_gmem *gmem, pgoff_t
> start,
> +				     pgoff_t end, bool need_split)
>  {
>  	bool flush = false, found_memslot = false;
>  	struct kvm_memory_slot *slot;
>  	struct kvm *kvm = gmem->kvm;
>  	unsigned long index;
> +	int ret = 0;
>  
>  	xa_for_each_range(&gmem->bindings, index, slot, start, end -
> 1) {
>  		pgoff_t pgoff = slot->gmem.pgoff;
> @@ -319,14 +320,23 @@ static void kvm_gmem_invalidate_begin(struct
> kvm_gmem *gmem, pgoff_t start,
>  			kvm_mmu_invalidate_begin(kvm);
>  		}
>  
> +		if (need_split) {
> +			ret = kvm_split_boundary_leafs(kvm,
> &gfn_range);
> +			if (ret < 0)
> +				goto out;
> +
> +			flush |= ret;
> +		}
>  		flush |= kvm_mmu_unmap_gfn_range(kvm, &gfn_range);
>  	}
>  
> +out:
>  	if (flush)
>  		kvm_flush_remote_tlbs(kvm);
>  
>  	if (found_memslot)
>  		KVM_MMU_UNLOCK(kvm);
> +	return 0;

Should return ret, not 0