linux-kernel - Re: [RFC v6 13/62] powerpc: track allocation status of all pkeys

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Message-Id: <20170729224305.GE5664@ram.oc3035372033.ibm.com>
Date:   Sat, 29 Jul 2017 15:43:05 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        arnd@...db.de, corbet@....net, mhocko@...nel.org,
        dave.hansen@...el.com, mingo@...hat.com, paulus@...ba.org,
        aneesh.kumar@...ux.vnet.ibm.com, akpm@...ux-foundation.org,
        khandual@...ux.vnet.ibm.com
Subject: Re: [RFC v6 13/62] powerpc: track allocation status of all pkeys

On Thu, Jul 27, 2017 at 11:01:44AM -0300, Thiago Jung Bauermann wrote:
> 
> Hello Ram,
> 
> I'm still going through the patches and haven't formed a full picture of
> the feature in my mind yet, so my comments today won't be particularly
> insightful...
> 
> But hopefully the comments that I currently have will be helpful anyway.

sure. thanx for taking the time to look through the patches.

> 
> Ram Pai <linuxram@...ibm.com> writes:
> > diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h
> > index 203d7de..09b268e 100644
> > --- a/arch/powerpc/include/asm/pkeys.h
> > +++ b/arch/powerpc/include/asm/pkeys.h
> > @@ -2,21 +2,87 @@
> >  #define _ASM_PPC64_PKEYS_H
> >
> >  extern bool pkey_inited;
> > -#define ARCH_VM_PKEY_FLAGS 0
> > +#define arch_max_pkey()  32
> > +#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \
> > +				VM_PKEY_BIT3 | VM_PKEY_BIT4)
> > +/*
> > + * Bits are in BE format.
> > + * NOTE: key 31, 1, 0 are not used.
> > + * key 0 is used by default. It give read/write/execute permission.
> > + * key 31 is reserved by the hypervisor.
> > + * key 1 is recommended to be not used.
> > + * PowerISA(3.0) page 1015, programming note.
> > + */
> > +#define PKEY_INITIAL_ALLOCAION  0xc0000001
> 
> There's a typo in the macro name, should be "ALLOCATION".

Thanks fixed it. The new version of the code, calculates the
allocation_mask at runtime, depending on the number of keys specified by
the device tree as well as other factors.  So the above macro is
replaced by a variable 'initial_allocation_mask'.

RP

> 
> -- 
> Thiago Jung Bauermann
> IBM Linux Technology Center

-- 
Ram Pai