Re: [PATCH v4 13/29] arm64: convert protection key into vm_flags and pgprot values

[Catalin Marinas <catalin.marinas@arm.com>]

On Thu, Jul 04, 2024 at 01:47:04PM +0100, Joey Gouly wrote:
> On Wed, Jun 19, 2024 at 05:45:29PM +0100, Catalin Marinas wrote:
> > On Tue, May 28, 2024 at 12:24:57PM +0530, Amit Daniel Kachhap wrote:
> > > On 5/3/24 18:31, Joey Gouly wrote:
> > > > diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
> > > > index 5966ee4a6154..ecb2d18dc4d7 100644
> > > > --- a/arch/arm64/include/asm/mman.h
> > > > +++ b/arch/arm64/include/asm/mman.h
> > > > @@ -7,7 +7,7 @@
> > > >   #include <uapi/asm/mman.h>
> > > >   static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
> > > > -	unsigned long pkey __always_unused)
> > > > +	unsigned long pkey)
> > > >   {
> > > >   	unsigned long ret = 0;
> > > > @@ -17,6 +17,12 @@ static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
> > > >   	if (system_supports_mte() && (prot & PROT_MTE))
> > > >   		ret |= VM_MTE;
> > > > +#if defined(CONFIG_ARCH_HAS_PKEYS)
> > > 
> > > Should there be system_supports_poe() check like above?
> > 
> > I think it should, otherwise we end up with these bits in the pte even
> > when POE is not supported.
> 
> I think it can't get here due to the flow of the code, but I will add it to be
> defensive (since it's just an alternative that gets patched).

You are probably right, the mprotect_pkey() will reject the call if we
don't support POE. So you could add a comment instead (but a
system_supports_poe() check seems safer).

> I still need the defined(CONFIG_ARCH_HAS_PKEYS) check, since the VM_PKEY_BIT*
> are only defined then.

Yes, the ifdef will stay.

-- 
Catalin