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b=c7kEKCt2emu8+T6n7qTfSORifJVoKQh2kg28pFXSWr0eYZyb/w6+Pb4ykjBXYLmm9 97jHgUVhwZWTzkgi/woAxVcFRSqNt76KPpYDjEo/EUHeq+X7Or7nKTgZZb078U0ARQ no/xsYpiTG0WZghM96EE7TUKcqUIvqG8ZqxE6LONBXzI1oEaB9ZSsCRi7YWonu52OK mYiGeIi4SmfWeptkTfY28Z5aL5e89Ptp3Wk4NECmiBSY/evwNnIG9qPCfRMJj6YBEZ 6xmANqqFEBrWPu+TgH7qlb/qozJe2OIv7rCaHx2IOvLG89vU7gWDeCHQGwDqPHiGPU Ijmj0CkpirSdg== Date: Thu, 28 Aug 2025 17:26:39 +0300 From: Mike Rapoport To: "Roy, Patrick" Cc: "david@redhat.com" , "seanjc@google.com" , "tabba@google.com" , "ackerleytng@google.com" , "pbonzini@redhat.com" , "kvm@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "will@kernel.org" , "vbabka@suse.cz" , "Cali, Marco" , "Kalyazin, Nikita" , "Thomson, Jack" , "Manwaring, Derek" Subject: Re: [PATCH v5 03/12] mm: introduce AS_NO_DIRECT_MAP Message-ID: References: <20250828093902.2719-1-roypat@amazon.co.uk> <20250828093902.2719-4-roypat@amazon.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250828093902.2719-4-roypat@amazon.co.uk> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: EF490180011 X-Stat-Signature: 3xs8wz6dgux99osr7fxpotm8pw57p8xc X-Rspam-User: X-HE-Tag: 1756391209-386366 X-HE-Meta: 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 whmq9Eoo t6X5cX4/KAxF1XcRNX1wm08CrVzIT2E32paBHO9wdBpLg1elujitnttUnJcdVv84W1mKvL90AAILYWS7pOtGCqCV+jkWyY6Yrc0Kj36VL3m3kUxT/23joy2nucYEOYFvpHX2vsdHOtV4e9brgDEhLKmH2Bam39ME04MBQdIyZMDK7v7PEgGzZxYDnTlMIKYBLra7BLULCLdAbHqDkarSkaburMi+GRuJdEagU2uspYPOuQrZHRU+g4AEUXGNAkC4I1PNiOfABv7qVhJRL4oZ4ZkckoIgU7ZYCgux8iHjrZgFw8fU5FYYOc6BWuQ7ejB0BW0BRRfBoyTTR/LaEbqMOJMJtHV5qIvc173/5WvYgB1prTMMKCzp1OI3f+2lIaHplLm7UUmysOocE5PjJqQJ/BhcgDA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 28, 2025 at 09:39:19AM +0000, Roy, Patrick wrote: > Add AS_NO_DIRECT_MAP for mappings where direct map entries of folios are > set to not present . Currently, mappings that match this description are > secretmem mappings (memfd_secret()). Later, some guest_memfd > configurations will also fall into this category. > > Reject this new type of mappings in all locations that currently reject > secretmem mappings, on the assumption that if secretmem mappings are > rejected somewhere, it is precisely because of an inability to deal with > folios without direct map entries, and then make memfd_secret() use > AS_NO_DIRECT_MAP on its address_space to drop its special > vma_is_secretmem()/secretmem_mapping() checks. > > This drops a optimization in gup_fast_folio_allowed() where > secretmem_mapping() was only called if CONFIG_SECRETMEM=y. secretmem is > enabled by default since commit b758fe6df50d ("mm/secretmem: make it on > by default"), so the secretmem check did not actually end up elided in > most cases anymore anyway. > > Use a new flag instead of overloading AS_INACCESSIBLE (which is already > set by guest_memfd) because not all guest_memfd mappings will end up > being direct map removed (e.g. in pKVM setups, parts of guest_memfd that > can be mapped to userspace should also be GUP-able, and generally not > have restrictions on who can access it). > > Signed-off-by: Patrick Roy > --- > include/linux/pagemap.h | 16 ++++++++++++++++ > include/linux/secretmem.h | 18 ------------------ > lib/buildid.c | 4 ++-- > mm/gup.c | 14 +++----------- > mm/mlock.c | 2 +- > mm/secretmem.c | 6 +----- > 6 files changed, 23 insertions(+), 37 deletions(-) > > diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h > index e918f96881f5..0ae1fb057b3d 100644 > --- a/include/linux/secretmem.h > +++ b/include/linux/secretmem.h > @@ -4,28 +4,10 @@ > > #ifdef CONFIG_SECRETMEM > > -extern const struct address_space_operations secretmem_aops; Please also make secretmem_aops static in mm/secretmem.c > -static inline bool secretmem_mapping(struct address_space *mapping) > -{ > - return mapping->a_ops == &secretmem_aops; > -} > - ... > diff --git a/mm/gup.c b/mm/gup.c > index adffe663594d..8c988e076e5d 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1234,7 +1234,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) > if ((gup_flags & FOLL_SPLIT_PMD) && is_vm_hugetlb_page(vma)) > return -EOPNOTSUPP; > > - if (vma_is_secretmem(vma)) > + if (vma_is_no_direct_map(vma)) > return -EFAULT; > > if (write) { > @@ -2751,7 +2751,6 @@ static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags) > { > bool reject_file_backed = false; > struct address_space *mapping; > - bool check_secretmem = false; > unsigned long mapping_flags; > > /* > @@ -2763,14 +2762,6 @@ static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags) > reject_file_backed = true; > > /* We hold a folio reference, so we can safely access folio fields. */ > - > - /* secretmem folios are always order-0 folios. */ > - if (IS_ENABLED(CONFIG_SECRETMEM) && !folio_test_large(folio)) > - check_secretmem = true; > - > - if (!reject_file_backed && !check_secretmem) > - return true; > - > if (WARN_ON_ONCE(folio_test_slab(folio))) > return false; There's a check for hugetlb after this and a comment there mentions secretmem, please update that to "mapping with no direct map" or something like that. -- Sincerely yours, Mike.