Re: [RFC PATCH 13/16] arm64: mm: Reset pkey in __tlb_remove_table()

Peter Zijlstra
2024-12-10T12:27:10Z

On Tue, Dec 10, 2024 at 10:28:44AM +0100, Kevin Brodsky wrote:
> On 09/12/2024 11:29, Peter Zijlstra wrote:
> > On Fri, Dec 06, 2024 at 10:11:07AM +0000, Kevin Brodsky wrote:
> >> [...]
> >>
> >> diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
> >> index a947c6e784ed..d1611ffa6d91 100644
> >> --- a/arch/arm64/include/asm/tlb.h
> >> +++ b/arch/arm64/include/asm/tlb.h
> >> @@ -10,10 +10,14 @@
> >>
> >> #include <linux/pagemap.h>
> >> #include <linux/swap.h>
> >> +#include <linux/kpkeys.h>
> >>
> >> static inline void __tlb_remove_table(void *_table)
> >> {
> >> - free_page_and_swap_cache((struct page *)_table);
> >> + struct page *page = (struct page *)_table;
> >> +
> >> + kpkeys_unprotect_pgtable_memory((unsigned long)page_address(page), 1);
> >> + free_page_and_swap_cache(page);
> >> }
> > Same as for the others, perhaps stick this in generic code instead of in
> > the arch code?
>
> This should be doable, with some refactoring. __tlb_remove_table() is
> currently called from two functions in mm/mmu_gather.c, I suppose I
> could create a wrapper there that calls
> kpkeys_unprotect_pgtable_memory() and then __tlb_remove_table(). Like in
> the p4d case I do however wonder how robust this is, as
> __tlb_remove_table() could end up being called from other places.

I don't foresee other __tlb_remove_table() users, this is all rather
speicific code. But if there ever were to be new users, it is something
they would have to take into consideration.