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

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Message-ID: <diqzplh2zktw.fsf@ackerleytng-ctop.c.googlers.com>
Date: Wed, 23 Apr 2025 13:25:47 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: Peter Xu <peterx@...hat.com>
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Subject: Re: [RFC PATCH 27/39] KVM: guest_memfd: Allow mmapping guest_memfd files

Peter Xu <peterx@...hat.com> writes:

> 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

Thank you for reviewing and helping me check on this!