Messages in this thread | | | From | Nadav Amit <> | Subject | Re: [PATCH 05/11] x86/mm: do not auto-massage page protections | Date | Fri, 23 Mar 2018 19:15:55 +0000 |
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Dave Hansen <dave.hansen@linux.intel.com> wrote:
> > From: Dave Hansen <dave.hansen@linux.intel.com> > > A PTE is constructed from a physical address and a pgprotval_t. > __PAGE_KERNEL, for instance, is a pgprot_t and must be converted > into a pgprotval_t before it can be used to create a PTE. This is > done implicitly within functions like set_pte() by massage_pgprot(). > > However, this makes it very challenging to set bits (and keep them > set) if your bit is being filtered out by massage_pgprot(). > > This moves the bit filtering out of set_pte() and friends. For
I don’t see that set_pte() filters the bits, so I am confused by this sentence...
> +static inline pgprotval_t check_pgprot(pgprot_t pgprot) > +{ > + pgprotval_t massaged_val = massage_pgprot(pgprot); > + > + /* mmdebug.h can not be included here because of dependencies */ > +#ifdef CONFIG_DEBUG_VM > + WARN_ONCE(pgprot_val(pgprot) != massaged_val, > + "attempted to set unsupported pgprot: %016lx " > + "bits: %016lx supported: %016lx\n", > + pgprot_val(pgprot), > + pgprot_val(pgprot) ^ massaged_val, > + __supported_pte_mask); > +#endif Why not to use VM_WARN_ON_ONCE() and avoid the ifdef?
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