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Date: Fri, 17 Feb 2017 09:21:47 -0800 From: Andy Lutomirski <luto@...capital.net> To: Dave Hansen <dave.hansen@...el.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>, "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>, linux-arch <linux-arch@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Catalin Marinas <catalin.marinas@....com>, Linux API <linux-api@...r.kernel.org> Subject: Re: [PATCHv3 33/33] mm, x86: introduce PR_SET_MAX_VADDR and PR_GET_MAX_VADDR On Fri, Feb 17, 2017 at 9:19 AM, Dave Hansen <dave.hansen@...el.com> wrote: > On 02/17/2017 06:13 AM, Kirill A. Shutemov wrote: >> +/* >> + * Default maximum virtual address. This is required for >> + * compatibility with applications that assumes 47-bit VA. >> + * The limit can be changed with prctl(PR_SET_MAX_VADDR). >> + */ >> +#define MAX_VADDR_DEFAULT ((1UL << 47) - PAGE_SIZE) > > This is a bit goofy. It's not the largest virtual adddress that can be > accessed, but the beginning of the last page. No, it really is the limit. We don't allow user code to map the last page because ti would be a root hole due to SYSRET. Thanks, Intel. See the comment near TASK_SIZE_MAX IIRC. --Andy
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