From: Andy Lutomirski <luto@kernel.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
moritz.lipp@iaik.tugraz.at,
Daniel Gruss <daniel.gruss@iaik.tugraz.at>,
michael.schwarz@iaik.tugraz.at,
richard.fellner@student.tugraz.at,
Andrew Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Kees Cook <keescook@google.com>, Hugh Dickins <hughd@google.com>,
X86 ML <x86@kernel.org>
Subject: Re: [PATCH 21/30] x86, mm: put mmu-to-h/w ASID translation in one place
Date: Fri, 10 Nov 2017 14:03:46 -0800 [thread overview]
Message-ID: <CALCETrXrXpTZE2sceBh=eW5kEP79hWc5iY36QKjfy=U4nTirDw@mail.gmail.com> (raw)
In-Reply-To: <20171110193146.5908BE13@viggo.jf.intel.com>
On Fri, Nov 10, 2017 at 11:31 AM, Dave Hansen
<dave.hansen@linux.intel.com> wrote:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> There are effectively two ASID types:
> 1. The one stored in the mmu_context that goes from 0->5
> 2. The one programmed into the hardware that goes from 1->6
>
> This consolidates the locations where converting beween the two
> (by doing +1) to a single place which gives us a nice place to
> comment. KAISER will also need to, given an ASID, know which
> hardware ASID to flush for the userspace mapping.
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Moritz Lipp <moritz.lipp@iaik.tugraz.at>
> Cc: Daniel Gruss <daniel.gruss@iaik.tugraz.at>
> Cc: Michael Schwarz <michael.schwarz@iaik.tugraz.at>
> Cc: Richard Fellner <richard.fellner@student.tugraz.at>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Kees Cook <keescook@google.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: x86@kernel.org
> ---
>
> b/arch/x86/include/asm/tlbflush.h | 30 ++++++++++++++++++------------
> 1 file changed, 18 insertions(+), 12 deletions(-)
>
> diff -puN arch/x86/include/asm/tlbflush.h~kaiser-pcid-pre-build-kern arch/x86/include/asm/tlbflush.h
> --- a/arch/x86/include/asm/tlbflush.h~kaiser-pcid-pre-build-kern 2017-11-10 11:22:16.521244931 -0800
> +++ b/arch/x86/include/asm/tlbflush.h 2017-11-10 11:22:16.525244931 -0800
> @@ -87,21 +87,26 @@ static inline u64 inc_mm_tlb_gen(struct
> */
> #define MAX_ASID_AVAILABLE ((1<<CR3_AVAIL_ASID_BITS) - 2)
>
> -/*
> - * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID
> - * bits. This serves two purposes. It prevents a nasty situation in
> - * which PCID-unaware code saves CR3, loads some other value (with PCID
> - * == 0), and then restores CR3, thus corrupting the TLB for ASID 0 if
> - * the saved ASID was nonzero. It also means that any bugs involving
> - * loading a PCID-enabled CR3 with CR4.PCIDE off will trigger
> - * deterministically.
> - */
> +static inline u16 kern_asid(u16 asid)
> +{
> + VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
> + /*
> + * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID
> + * bits. This serves two purposes. It prevents a nasty situation in
> + * which PCID-unaware code saves CR3, loads some other value (with PCID
> + * == 0), and then restores CR3, thus corrupting the TLB for ASID 0 if
> + * the saved ASID was nonzero. It also means that any bugs involving
> + * loading a PCID-enabled CR3 with CR4.PCIDE off will trigger
> + * deterministically.
> + */
> + return asid + 1;
> +}
This seems really error-prone. Maybe we should have a pcid_t type and
make all the interfaces that want a h/w PCID take pcid_t.
--Andy
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next prev parent reply other threads:[~2017-11-10 22:04 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-10 19:30 [PATCH 00/30] [v3] KAISER: unmap most of the kernel from userspace page tables Dave Hansen
2017-11-10 19:31 ` [PATCH 01/30] x86, mm: do not set _PAGE_USER for init_mm " Dave Hansen
2017-11-10 19:31 ` [PATCH 02/30] x86, tlb: Make CR4-based TLB flushes more robust Dave Hansen
2017-11-10 19:31 ` [PATCH 03/30] x86/mm: Document X86_CR4_PGE toggling behavior Dave Hansen
2017-11-10 19:31 ` [PATCH 04/30] x86, kaiser: disable global pages by default with KAISER Dave Hansen
2017-11-14 19:38 ` Rik van Riel
2017-11-26 14:48 ` Ingo Molnar
2017-11-27 11:37 ` Thomas Gleixner
2017-11-27 13:20 ` [PATCH v2] x86/mm/kaiser: Disable " Ingo Molnar
2017-11-27 13:23 ` Thomas Gleixner
2017-11-27 13:27 ` Ingo Molnar
2017-11-10 19:31 ` [PATCH 05/30] x86, kaiser: prepare assembly for entry/exit CR3 switching Dave Hansen
2017-11-20 12:17 ` Thomas Gleixner
2017-11-10 19:31 ` [PATCH 06/30] x86, kaiser: introduce user-mapped per-cpu areas Dave Hansen
2017-11-10 19:31 ` [PATCH 07/30] x86, kaiser: mark per-cpu data structures required for entry/exit Dave Hansen
2017-11-10 19:31 ` [PATCH 08/30] x86, kaiser: unmap kernel from userspace page tables (core patch) Dave Hansen
2017-11-20 17:21 ` Thomas Gleixner
2017-11-22 22:45 ` Dave Hansen
2017-11-22 22:50 ` Dave Hansen
2017-11-22 22:54 ` Dave Hansen
2017-11-22 23:11 ` Dave Hansen
2017-11-10 19:31 ` [PATCH 09/30] x86, kaiser: only populate shadow page tables for userspace Dave Hansen
2017-11-20 20:12 ` Thomas Gleixner
2017-11-21 7:05 ` Ingo Molnar
2017-11-21 22:09 ` Dave Hansen
2017-11-22 3:44 ` Andy Lutomirski
2017-11-22 23:30 ` Dave Hansen
2017-11-10 19:31 ` [PATCH 10/30] x86, kaiser: allow NX poison to be set in p4d/pgd Dave Hansen
2017-11-10 19:31 ` [PATCH 11/30] x86, kaiser: make sure static PGDs are 8k in size Dave Hansen
2017-11-10 19:31 ` [PATCH 12/30] x86, kaiser: map GDT into user page tables Dave Hansen
2017-11-20 20:22 ` Thomas Gleixner
2017-11-20 20:46 ` Andy Lutomirski
2017-11-20 20:55 ` Thomas Gleixner
2017-11-21 21:19 ` Dave Hansen
2017-11-21 22:46 ` Andy Lutomirski
2017-11-21 23:17 ` Dave Hansen
2017-11-21 23:32 ` Andy Lutomirski
2017-11-21 23:42 ` Dave Hansen
2017-11-22 0:17 ` Andy Lutomirski
2017-11-22 0:37 ` Dave Hansen
2017-11-21 22:12 ` Dave Hansen
2017-11-10 19:31 ` [PATCH 13/30] x86, kaiser: map dynamically-allocated LDTs Dave Hansen
2017-11-10 19:31 ` [PATCH 14/30] x86, kaiser: map espfix structures Dave Hansen
2017-11-10 19:31 ` [PATCH 15/30] x86, kaiser: map entry stack variables Dave Hansen
2017-11-10 19:31 ` [PATCH 16/30] x86, kaiser: map trace interrupt entry Dave Hansen
2017-11-10 19:31 ` [PATCH 17/30] x86, kaiser: map debug IDT tables Dave Hansen
2017-11-20 20:40 ` Thomas Gleixner
2017-11-21 22:16 ` Dave Hansen
2017-11-20 20:44 ` Andy Lutomirski
2017-11-20 20:54 ` Thomas Gleixner
2017-11-10 19:31 ` [PATCH 18/30] x86, kaiser: map virtually-addressed performance monitoring buffers Dave Hansen
2017-11-14 18:20 ` Peter Zijlstra
2017-11-14 18:28 ` Dave Hansen
2017-11-14 19:10 ` Hugh Dickins
2017-11-14 19:24 ` Andy Lutomirski
2017-11-15 9:41 ` Peter Zijlstra
2017-11-10 19:31 ` [PATCH 19/30] x86, mm: Move CR3 construction functions Dave Hansen
2017-11-10 19:31 ` [PATCH 20/30] x86, mm: remove hard-coded ASID limit checks Dave Hansen
2017-11-20 20:47 ` Thomas Gleixner
2017-11-10 19:31 ` [PATCH 21/30] x86, mm: put mmu-to-h/w ASID translation in one place Dave Hansen
2017-11-10 22:03 ` Andy Lutomirski [this message]
2017-11-10 22:09 ` Dave Hansen
2017-11-10 22:10 ` Andy Lutomirski
2017-11-10 19:31 ` [PATCH 22/30] x86, pcid, kaiser: allow flushing for future ASID switches Dave Hansen
2017-11-10 19:31 ` [PATCH 23/30] x86, kaiser: use PCID feature to make user and kernel switches faster Dave Hansen
2017-11-16 19:19 ` Andrea Arcangeli
2017-11-16 19:25 ` Dave Hansen
2017-11-10 19:31 ` [PATCH 24/30] x86, kaiser: disable native VSYSCALL Dave Hansen
2017-11-10 19:31 ` [PATCH 25/30] x86, kaiser: add debugfs file to turn KAISER on/off at runtime Dave Hansen
2017-11-10 19:31 ` [PATCH 26/30] x86, kaiser: add a function to check for KAISER being enabled Dave Hansen
2017-11-10 19:31 ` [PATCH 27/30] x86, kaiser: un-poison PGDs at runtime Dave Hansen
2017-11-10 19:31 ` [PATCH 28/30] x86, kaiser: allow KAISER to be enabled/disabled " Dave Hansen
2017-11-10 19:32 ` [PATCH 29/30] x86, kaiser: add Kconfig Dave Hansen
2017-11-10 19:32 ` [PATCH 30/30] x86, kaiser, xen: Dynamically disable KAISER when running under Xen PV Dave Hansen
2017-11-20 16:02 ` [PATCH 00/30] [v3] KAISER: unmap most of the kernel from userspace page tables Juerg Haefliger
-- strict thread matches above, loose matches on Subject: below --
2017-11-08 19:46 [PATCH 00/30] [v2] " Dave Hansen
2017-11-08 19:47 ` [PATCH 21/30] x86, mm: put mmu-to-h/w ASID translation in one place Dave Hansen
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