From: Dave Hansen <dave@sr71.net> To: Ingo Molnar <mingo@kernel.org> Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Thomas Gleixner <tglx@linutronix.de> Subject: Re: [PATCH 10/26] x86, pkeys: notify userspace about protection key faults Date: Sun, 27 Sep 2015 15:39:58 -0700 [thread overview] Message-ID: <5608703E.5070406@sr71.net> (raw) In-Reply-To: <20150926062023.GB27841@gmail.com> On 09/25/2015 11:20 PM, Ingo Molnar wrote: > * Dave Hansen <dave@sr71.net> wrote: ... >> Since follow_pte() fails for all huge >> pages, it just falls back to pulling the protection key out of the VMA, >> which _does_ work for huge pages. > > That might be true for explicit hugetlb vmas, but what about transparent hugepages > that can show up in regular vmas? All PTEs (large or small) established under a given VMA have the same protection key. Any change in protection key for a range will either change or split the VMA. So I think it's safe to rely on the VMA entirely. Well, as least as safe as the PTE. It's definitely a wee bit racy, which I'll elaborate on when I repost the patches. >> I've actually removed the PTE walking and I just now use the VMA directly. I >> don't see a ton of additional value from walking the page tables when we can get >> what we need from the VMA. > > That's actually good, because it's also cheap, especially if we can get rid of the > extra find_vma(). > > and we (thankfully) have no non-linear vmas to worry about anymore. Yep.
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From: Dave Hansen <dave@sr71.net> To: Ingo Molnar <mingo@kernel.org> Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Thomas Gleixner <tglx@linutronix.de> Subject: Re: [PATCH 10/26] x86, pkeys: notify userspace about protection key faults Date: Sun, 27 Sep 2015 15:39:58 -0700 [thread overview] Message-ID: <5608703E.5070406@sr71.net> (raw) In-Reply-To: <20150926062023.GB27841@gmail.com> On 09/25/2015 11:20 PM, Ingo Molnar wrote: > * Dave Hansen <dave@sr71.net> wrote: ... >> Since follow_pte() fails for all huge >> pages, it just falls back to pulling the protection key out of the VMA, >> which _does_ work for huge pages. > > That might be true for explicit hugetlb vmas, but what about transparent hugepages > that can show up in regular vmas? All PTEs (large or small) established under a given VMA have the same protection key. Any change in protection key for a range will either change or split the VMA. So I think it's safe to rely on the VMA entirely. Well, as least as safe as the PTE. It's definitely a wee bit racy, which I'll elaborate on when I repost the patches. >> I've actually removed the PTE walking and I just now use the VMA directly. I >> don't see a ton of additional value from walking the page tables when we can get >> what we need from the VMA. > > That's actually good, because it's also cheap, especially if we can get rid of the > extra find_vma(). > > and we (thankfully) have no non-linear vmas to worry about anymore. Yep. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-09-27 22:40 UTC|newest] Thread overview: 172+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-09-16 17:49 [PATCH 00/26] [RFCv2] x86: Memory Protection Keys Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 04/26] x86, pku: define new CR4 bit Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 03/26] x86, pkeys: cpuid bit definition Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 02/26] x86, pkeys: Add Kconfig option Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 01/26] x86, fpu: add placeholder for Processor Trace XSAVE state Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 07/26] x86, pkeys: new page fault error code bit: PF_PK Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 05/26] x86, pkey: add PKRU xsave fields and data structure(s) Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-22 19:53 ` Thomas Gleixner 2015-09-22 19:53 ` Thomas Gleixner 2015-09-22 19:58 ` Dave Hansen 2015-09-22 19:58 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 06/26] x86, pkeys: PTE bits for storing protection key Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 10/26] x86, pkeys: notify userspace about protection key faults Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-22 20:03 ` Thomas Gleixner 2015-09-22 20:03 ` Thomas Gleixner 2015-09-22 20:21 ` Dave Hansen 2015-09-22 20:21 ` Dave Hansen 2015-09-22 20:27 ` Thomas Gleixner 2015-09-22 20:27 ` Thomas Gleixner 2015-09-22 20:29 ` Dave Hansen 2015-09-22 20:29 ` Dave Hansen 2015-09-23 8:05 ` Ingo Molnar 2015-09-23 8:05 ` Ingo Molnar 2015-09-24 9:23 ` Ingo Molnar 2015-09-24 9:23 ` Ingo Molnar 2015-09-24 9:30 ` Ingo Molnar 2015-09-24 9:30 ` Ingo Molnar 2015-09-24 17:41 ` Dave Hansen 2015-09-24 17:41 ` Dave Hansen 2015-09-25 7:11 ` Ingo Molnar 2015-09-25 7:11 ` Ingo Molnar 2015-09-25 23:18 ` Dave Hansen 2015-09-25 23:18 ` Dave Hansen 2015-09-26 6:20 ` Ingo Molnar 2015-09-26 6:20 ` Ingo Molnar 2015-09-27 22:39 ` Dave Hansen [this message] 2015-09-27 22:39 ` Dave Hansen 2015-09-28 5:59 ` Ingo Molnar 2015-09-28 5:59 ` Ingo Molnar 2015-09-24 17:15 ` Dave Hansen 2015-09-24 17:15 ` Dave Hansen 2015-09-28 19:25 ` Christian Borntraeger 2015-09-28 19:25 ` Christian Borntraeger 2015-09-28 19:32 ` Dave Hansen 2015-09-28 19:32 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 09/26] x86, pkeys: arch-specific protection bits Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 08/26] x86, pkeys: store protection in high VMA flags Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 11/26] x86, pkeys: add functions for set/fetch PKRU Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-22 20:05 ` Thomas Gleixner 2015-09-22 20:05 ` Thomas Gleixner 2015-09-22 20:22 ` Dave Hansen 2015-09-22 20:22 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 14/26] x86, pkeys: check VMAs and PTEs for protection keys Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 12/26] mm: factor out VMA fault permission checking Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 13/26] mm: simplify get_user_pages() PTE bit handling Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 15/26] x86, pkeys: optimize fault handling in access_error() Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 16/26] x86, pkeys: dump PKRU with other kernel registers Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 17/26] x86, pkeys: dump PTE pkey in /proc/pid/smaps Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 19/26] [NEWSYSCALL] mm, multi-arch: pass a protection key in to calc_vm_flag_bits() Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 20/26] [NEWSYSCALL] mm: implement new mprotect_pkey() system call Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 18/26] x86, pkeys: add Kconfig prompt to existing config option Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 22/26] [HIJACKPROT] mm: Pass the 4-bit protection key in via PROT_ bits to syscalls Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 21/26] [NEWSYSCALL] x86: wire up mprotect_key() system call Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 24/26] [HIJACKPROT] x86, pkeys: mask off pkeys bits in mprotect() Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 25/26] x86, pkeys: actually enable Memory Protection Keys in CPU Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 23/26] [HIJACKPROT] x86, pkeys: add x86 version of arch_validate_prot() Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-16 17:49 ` [PATCH 26/26] x86, pkeys: Documentation Dave Hansen 2015-09-16 17:49 ` Dave Hansen 2015-09-20 8:55 ` Ingo Molnar 2015-09-20 8:55 ` Ingo Molnar 2015-09-21 4:34 ` Dave Hansen 2015-09-21 4:34 ` Dave Hansen 2015-09-24 9:49 ` Ingo Molnar 2015-09-24 9:49 ` Ingo Molnar 2015-09-24 19:10 ` Dave Hansen 2015-09-24 19:10 ` Dave Hansen 2015-09-24 19:17 ` Andy Lutomirski 2015-09-24 19:17 ` Andy Lutomirski 2015-09-25 7:16 ` Ingo Molnar 2015-09-25 7:16 ` Ingo Molnar 2015-09-25 6:15 ` Ingo Molnar 2015-09-25 6:15 ` Ingo Molnar 2015-10-01 11:17 ` Ingo Molnar 2015-10-01 11:17 ` Ingo Molnar 2015-10-01 20:39 ` Kees Cook 2015-10-01 20:39 ` Kees Cook 2015-10-01 20:45 ` Andy Lutomirski 2015-10-01 20:45 ` Andy Lutomirski 2015-10-02 6:23 ` Ingo Molnar 2015-10-02 6:23 ` Ingo Molnar 2015-10-02 17:50 ` Dave Hansen 2015-10-02 17:50 ` Dave Hansen 2015-10-03 7:27 ` Ingo Molnar 2015-10-03 7:27 ` Ingo Molnar 2015-10-06 23:28 ` Dave Hansen 2015-10-06 23:28 ` Dave Hansen 2015-10-07 7:11 ` Ingo Molnar 2015-10-07 7:11 ` Ingo Molnar 2015-10-16 15:12 ` Dave Hansen 2015-10-16 15:12 ` Dave Hansen 2015-10-21 18:55 ` Andy Lutomirski 2015-10-21 18:55 ` Andy Lutomirski 2015-10-21 19:11 ` Dave Hansen 2015-10-21 19:11 ` Dave Hansen 2015-10-21 23:22 ` Andy Lutomirski 2015-10-21 23:22 ` Andy Lutomirski 2015-10-01 20:58 ` Dave Hansen 2015-10-01 20:58 ` Dave Hansen 2015-10-01 22:33 ` Dave Hansen 2015-10-01 22:35 ` Kees Cook 2015-10-01 22:35 ` Kees Cook 2015-10-01 22:39 ` Dave Hansen 2015-10-01 22:39 ` Dave Hansen 2015-10-01 22:48 ` Linus Torvalds 2015-10-01 22:48 ` Linus Torvalds 2015-10-01 22:56 ` Dave Hansen 2015-10-01 22:56 ` Dave Hansen 2015-10-02 1:38 ` Linus Torvalds 2015-10-02 1:38 ` Linus Torvalds 2015-10-02 18:08 ` Dave Hansen 2015-10-02 18:08 ` Dave Hansen 2015-10-02 7:09 ` Ingo Molnar 2015-10-02 7:09 ` Ingo Molnar 2015-10-03 6:59 ` Ingo Molnar 2015-10-03 6:59 ` Ingo Molnar 2015-10-02 11:49 ` Paolo Bonzini 2015-10-02 11:49 ` Paolo Bonzini 2015-10-02 11:58 ` Linus Torvalds 2015-10-02 11:58 ` Linus Torvalds 2015-10-02 12:14 ` Paolo Bonzini 2015-10-02 12:14 ` Paolo Bonzini 2015-10-03 6:46 ` Ingo Molnar 2015-10-03 6:46 ` Ingo Molnar 2015-10-01 22:57 ` Andy Lutomirski 2015-10-01 22:57 ` Andy Lutomirski 2015-10-02 6:09 ` Ingo Molnar 2015-10-02 6:09 ` Ingo Molnar 2015-10-03 8:17 ` Ingo Molnar 2015-10-03 8:17 ` Ingo Molnar 2015-10-07 20:24 ` Dave Hansen 2015-10-07 20:24 ` Dave Hansen 2015-10-07 20:39 ` Andy Lutomirski 2015-10-07 20:39 ` Andy Lutomirski 2015-10-07 20:47 ` Dave Hansen 2015-10-07 20:47 ` Dave Hansen 2015-09-16 17:51 ` Fwd: [PATCH 00/26] [RFCv2] x86: Memory Protection Keys Dave Hansen
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