Messages in this thread | | | Date | Tue, 7 May 2024 13:34:36 +0100 | Subject | Re: [PATCH v4 1/4] arm64/mm: generalize PMD_PRESENT_INVALID for all levels | From | Ryan Roberts <> |
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On 07/05/2024 12:38, David Hildenbrand wrote: > On 03.05.24 16:45, Ryan Roberts wrote: >> As preparation for the next patch, which frees up the PTE_PROT_NONE >> present pte and swap pte bit, generalize PMD_PRESENT_INVALID to >> PTE_PRESENT_INVALID. This will then be used to mark PROT_NONE ptes (and >> entries at any other level) in the next patch. >> >> While we're at it, fix up the swap pte format comment to include >> PTE_PRESENT_INVALID. This is not new, it just wasn't previously >> documented. >> >> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> >> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> >> --- >> arch/arm64/include/asm/pgtable-prot.h | 8 ++++---- >> arch/arm64/include/asm/pgtable.h | 21 ++++++++++++--------- >> 2 files changed, 16 insertions(+), 13 deletions(-) >> >> diff --git a/arch/arm64/include/asm/pgtable-prot.h >> b/arch/arm64/include/asm/pgtable-prot.h >> index dd9ee67d1d87..cdbf51eef7a6 100644 >> --- a/arch/arm64/include/asm/pgtable-prot.h >> +++ b/arch/arm64/include/asm/pgtable-prot.h >> @@ -21,11 +21,11 @@ >> #define PTE_PROT_NONE (_AT(pteval_t, 1) << 58) /* only when >> !PTE_VALID */ >> /* >> - * This bit indicates that the entry is present i.e. pmd_page() >> - * still points to a valid huge page in memory even if the pmd >> - * has been invalidated. >> + * PTE_PRESENT_INVALID=1 & PTE_VALID=0 indicates that the pte's fields should be >> + * interpreted according to the HW layout by SW but any attempted HW access to >> + * the address will result in a fault. pte_present() returns true. >> */ >> -#define PMD_PRESENT_INVALID (_AT(pteval_t, 1) << 59) /* only when >> !PMD_SECT_VALID */ >> +#define PTE_PRESENT_INVALID (_AT(pteval_t, 1) << 59) /* only when >> !PTE_VALID */ > > Ah, so PTE_VALID == PMD_SECT_VALID. Would that also be a reasonable > generalization independent of this? (or do we keep it as is because it's a HW def?)
To be honest, I'm not sure of the history, but some things are implemented as wrappers around pte functions and others are implemented specifically for pmd/pud/etc.
On arm64, block mappings (all levels except last level) have the same HW format as page mappings (last level) except that bit 1 must be 0 for block and 1 for page. And with this series, SW/non-present bits are all matching too. So my vote would be to harmonise toward a single implementation in future (modulus the bit 1 problem), which would include getting rid of things like PMD_SECT_VALID.
> > Reviewed-by: David Hildenbrand <david@redhat.com>
Thanks for all the R-bs!
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