Messages in this thread | | | Date | Tue, 30 Apr 2024 13:53:32 +0100 | Subject | Re: [PATCH v2 1/3] arm64/mm: Refactor PMD_PRESENT_INVALID and PTE_PROT_NONE bits | From | Ryan Roberts <> |
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On 30/04/2024 12:37, David Hildenbrand wrote: > On 30.04.24 13:11, Catalin Marinas wrote: >> On Mon, Apr 29, 2024 at 06:15:45PM +0100, Ryan Roberts wrote: >>> On 29/04/2024 17:20, Catalin Marinas wrote: >>>> On Mon, Apr 29, 2024 at 03:02:05PM +0100, Ryan Roberts wrote: >>>>> diff --git a/arch/arm64/include/asm/pgtable-prot.h >>>>> b/arch/arm64/include/asm/pgtable-prot.h >>>>> index dd9ee67d1d87..de62e6881154 100644 >>>>> --- a/arch/arm64/include/asm/pgtable-prot.h >>>>> +++ b/arch/arm64/include/asm/pgtable-prot.h >>>>> @@ -18,14 +18,7 @@ >>>>> #define PTE_DIRTY (_AT(pteval_t, 1) << 55) >>>>> #define PTE_SPECIAL (_AT(pteval_t, 1) << 56) >>>>> #define PTE_DEVMAP (_AT(pteval_t, 1) << 57) >>>>> -#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. >>>>> - */ >>>>> -#define PMD_PRESENT_INVALID (_AT(pteval_t, 1) << 59) /* only when >>>>> !PMD_SECT_VALID */ >>>>> +#define PTE_INVALID (_AT(pteval_t, 1) << 59) /* only when >>>>> !PTE_VALID */ >>>> >>>> Nitpick - I prefer the PTE_PRESENT_INVALID name as it makes it clearer >>>> it's a present pte. We already have PTE_VALID, calling it PTE_INVALID >>>> looks like a negation only. >>> >>> Meh, for me the pte can only be valid or invalid if it is present. So it's >>> implicit. And if you have PTE_PRESENT_INVALID you should also have >>> PTE_PRESENT_VALID. >>> >>> We also have pte_mkinvalid(), which is core-mm-defined. In your scheme, surely >>> it should be pte_mkpresent_invalid()? >>> >>> But you're the boss, I'll change this to PTE_PRESENT_INVALID. :-( >> >> TBH, I don't have a strong opinion but best to avoid the bikeshedding. >> I'll leave the decision to you ;). It would match the pmd_mkinvalid() >> core code. But if you drop 'present' make sure you add a comment above >> that it's meant for present ptes. > > FWIW, I was confused by > > present = valid | invalid
OK fair enough.
> > Something like > > present = present_valid | present_invalid
I don't want to change pte_valid() to pte_present_valid(); that would also be a fair bit of churn.
I'll take Catalin's suggestion and make this PTE_PRESENT_INVALID and pte_present_invalid(). And obviously leave pmd_mkinvalid() as it is. (Conversation in the other thread has concluded that it's ok to invalidate a non-present pmd afterall).
> > would be more obvious at least to me ;) >
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