linux-kernel - Re: [RFC PATCH 27/39] KVM: guest_memfd: Allow mmapping guest

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Message-ID: <Z47RSls2rr-xVqNk@x1n>
Date: Mon, 20 Jan 2025 17:42:18 -0500
From: Peter Xu <peterx@...hat.com>
To: Ackerley Tng <ackerleytng@...gle.com>
Cc: tabba@...gle.com, quic_eberman@...cinc.com, roypat@...zon.co.uk,
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Subject: Re: [RFC PATCH 27/39] KVM: guest_memfd: Allow mmapping guest_memfd
 files

On Tue, Sep 10, 2024 at 11:43:58PM +0000, Ackerley Tng wrote:
> @@ -790,6 +791,9 @@ static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
>  	 */
>  	filemap_invalidate_lock(inode->i_mapping);
>  
> +	/* TODO: Check if even_cows should be 0 or 1 */
> +	unmap_mapping_range(inode->i_mapping, start, len, 0);
> +
>  	list_for_each_entry(gmem, gmem_list, entry)
>  		kvm_gmem_invalidate_begin(gmem, start, end);
>  
> @@ -946,6 +950,9 @@ static void kvm_gmem_hugetlb_teardown(struct inode *inode)
>  {
>  	struct kvm_gmem_hugetlb *hgmem;
>  
> +	/* TODO: Check if even_cows should be 0 or 1 */
> +	unmap_mapping_range(inode->i_mapping, 0, LLONG_MAX, 0);

Setting to 0 is ok in both places: even_cows only applies to MAP_PRIVATE,
which gmemfd doesn't support.  So feel free to drop the two comment lines.

Thanks,

-- 
Peter Xu