Message-ID: <094591b6-97eb-4cae-aa08-fececcba4ba1@amazon.com>
Date: Thu, 15 Jan 2026 15:25:27 +0000
From: Nikita Kalyazin <kalyazin@...zon.com>
To: Heiko Carstens <hca@...ux.ibm.com>, "Kalyazin, Nikita"
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Subject: Re: [PATCH v9 01/13] set_memory: add folio_{zap, restore}_direct_map
 helpers



On 15/01/2026 12:12, Heiko Carstens wrote:
> On Wed, Jan 14, 2026 at 01:45:23PM +0000, Kalyazin, Nikita wrote:
>> From: Nikita Kalyazin <kalyazin@...zon.com>
>>
>> These allow guest_memfd to remove its memory from the direct map.
>> Only implement them for architectures that have direct map.
>> In folio_zap_direct_map(), flush TLB on architectures where
>> set_direct_map_valid_noflush() does not flush it internally.
> 
> ...
> 
>> diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
>> index d3ce04a4b248..df4a487b484d 100644
>> --- a/arch/s390/mm/pageattr.c
>> +++ b/arch/s390/mm/pageattr.c
>> @@ -412,6 +412,24 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
>>        return __set_memory((unsigned long)page_to_virt(page), nr, flags);
>>   }
>>
>> +int folio_zap_direct_map(struct folio *folio)
>> +{
>> +     unsigned long addr = (unsigned long)folio_address(folio);
>> +     int ret;
>> +
>> +     ret = set_direct_map_valid_noflush(folio_page(folio, 0),
>> +                                        folio_nr_pages(folio), false);
>> +     flush_tlb_kernel_range(addr, addr + folio_size(folio));
>> +
>> +     return ret;
>> +}
> 
> The instructions used in the s390 implementation of
> set_direct_map_valid_noflush() do flush TLB entries.
> The extra flush_tlb_kernel_range() is not required.

Thanks, Heiko.  Will update in the next version.

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