linux-kernel - Re: [RFC, PATCH 16/22] x86/mm: Preserve KeyID on pte_modify() and pgprot

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Message-ID: <20180306083008.6dklty5oq3pbzxuo@node.shutemov.name>
Date:   Tue, 6 Mar 2018 11:30:08 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC, PATCH 16/22] x86/mm: Preserve KeyID on pte_modify() and
 pgprot_modify()

On Mon, Mar 05, 2018 at 11:09:23AM -0800, Dave Hansen wrote:
> On 03/05/2018 08:26 AM, Kirill A. Shutemov wrote:
> > + * It includes full range of PFN bits regardless if they were claimed for KeyID
> > + * or not: we want to preserve KeyID on pte_modify() and pgprot_modify().
> >   */
> > -#define _PAGE_CHG_MASK	(PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT |		\
> > +#define PTE_PFN_MASK_MAX \
> > +	(((signed long)PAGE_MASK) & ((1UL << __PHYSICAL_MASK_SHIFT) - 1))
> > +#define _PAGE_CHG_MASK	(PTE_PFN_MASK_MAX | _PAGE_PCD | _PAGE_PWT |		\
> >  			 _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY |	\
> >  			 _PAGE_SOFT_DIRTY)
> 
> Is there a way to make this:
> 
> #define _PAGE_CHG_MASK	(PTE_PFN_MASK | PTE_KEY_MASK...? | _PAGE_PCD |
> 
> That would be a lot more understandable.

Yes, it would.

But it means we will have *two* variables referenced from _PAGE_CHG_MASK:
one for PTE_PFN_MASK and one for PTE_KEY_MASK as both of them are dynamic.

With this patch we would get rid of both of them.

I'll update the description.

-- 
 Kirill A. Shutemov