linux-kernel - Re: [PATCH, RFC 09/62] x86/mm: Preserve KeyID on pte_modify() and pgprot

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Date:   Fri, 14 Jun 2019 11:15:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC 09/62] x86/mm: Preserve KeyID on pte_modify() and
 pgprot_modify()

On Wed, May 08, 2019 at 05:43:29PM +0300, Kirill A. Shutemov wrote:
> + * Cast PAGE_MASK to a signed type so that it is sign-extended if
> + * virtual addresses are 32-bits but physical addresses are larger
> + * (ie, 32-bit PAE).

On 32bit, 'long' is still 32bit, did you want to cast to 'long long'
instead? Ideally we'd use pteval_t here, but I see that is unsigned.

>   */
> -#define _PAGE_CHG_MASK	(PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT |		\
> +#define PTE_PFN_MASK_MAX \
> +	(((signed long)PAGE_MASK) & ((1ULL << __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 | _PAGE_DEVMAP)
>  #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE)