"Kalyazin, Nikita" <[email protected]> writes: > From: Nikita Kalyazin <[email protected]> > > 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. > > The new helpers need to be accessible to KVM on architectures that > support guest_memfd (x86 and arm64). Since arm64 does not support > building KVM as a module, only export them on x86. > > Direct map removal gives guest_memfd the same protection that > memfd_secret does, such as hardening against Spectre-like attacks > through in-kernel gadgets. > > Signed-off-by: Nikita Kalyazin <[email protected]> > --- > arch/arm64/include/asm/set_memory.h | 2 ++ > arch/arm64/mm/pageattr.c | 12 ++++++++++++ > arch/loongarch/include/asm/set_memory.h | 2 ++ > arch/loongarch/mm/pageattr.c | 16 ++++++++++++++++ > arch/riscv/include/asm/set_memory.h | 2 ++ > arch/riscv/mm/pageattr.c | 16 ++++++++++++++++ > arch/s390/include/asm/set_memory.h | 2 ++ > arch/s390/mm/pageattr.c | 18 ++++++++++++++++++ > arch/x86/include/asm/set_memory.h | 2 ++ > arch/x86/mm/pat/set_memory.c | 20 ++++++++++++++++++++ > include/linux/set_memory.h | 10 ++++++++++ > 11 files changed, 102 insertions(+) > > diff --git a/arch/arm64/include/asm/set_memory.h > b/arch/arm64/include/asm/set_memory.h > index 90f61b17275e..d949f1deb701 100644 > --- a/arch/arm64/include/asm/set_memory.h > +++ b/arch/arm64/include/asm/set_memory.h > @@ -14,6 +14,8 @@ int set_memory_valid(unsigned long addr, int numpages, int > enable); > int set_direct_map_invalid_noflush(struct page *page); > int set_direct_map_default_noflush(struct page *page); > int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid); > +int folio_zap_direct_map(struct folio *folio); > +int folio_restore_direct_map(struct folio *folio); > bool kernel_page_present(struct page *page); > > int set_memory_encrypted(unsigned long addr, int numpages); > diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c > index f0e784b963e6..a94eff324dda 100644 > --- a/arch/arm64/mm/pageattr.c > +++ b/arch/arm64/mm/pageattr.c > @@ -357,6 +357,18 @@ int set_direct_map_valid_noflush(struct page *page, > unsigned nr, bool valid) > return set_memory_valid(addr, nr, valid); > } > > +int folio_zap_direct_map(struct folio *folio) > +{ > + return set_direct_map_valid_noflush(folio_page(folio, 0), > + folio_nr_pages(folio), false); > +} > + > +int folio_restore_direct_map(struct folio *folio) > +{ > + return set_direct_map_valid_noflush(folio_page(folio, 0), > + folio_nr_pages(folio), true); > +} > +
Was going to suggest a _noflush suffix to these functions, but saw Aneesh's comment that these functions actually do flush_tlb_kernel [1] [1] https://lore.kernel.org/all/[email protected]/ Reviewed-by: Ackerley Tng <[email protected]> > #ifdef CONFIG_DEBUG_PAGEALLOC > /* > * This is - apart from the return value - doing the same > > [...snip...] >
