From: Thomas Gleixner <tglx@linutronix.de>
To: Ren Qiaowei <qiaowei.ren@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-mips@linux-mips.org
Subject: Re: [PATCH v9 11/12] x86, mpx: cleanup unused bound tables
Date: Mon, 27 Oct 2014 21:49:01 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1410272138540.5308@nanos> (raw)
In-Reply-To: <544DB873.1010207@intel.com>
On Mon, 27 Oct 2014, Ren Qiaowei wrote:
> If so, I guess that there are some questions needed to be considered:
>
> 1) Almost all palces which call do_munmap() will need to add
> mpx_pre_unmap/post_unmap calls, like vm_munmap(), mremap(), shmdt(), etc..
What's the problem with that?
> 2) before mpx_post_unmap() call, it is possible for those bounds tables within
> mm->bd_remove_vmas to be re-used.
>
> In this case, userspace may do new mapping and access one address which will
> cover one of those bounds tables. During this period, HW will check if one
> bounds table exist, if yes one fault won't be produced.
Errm. Before user space can use the bounds table for the new mapping
it needs to add the entries, right? So:
CPU 0 CPU 1
down_write(mm->bd_sem);
mpx_pre_unmap();
clear bounds directory entries
unmap();
map()
write_bounds_entry()
trap()
down_read(mm->bd_sem);
mpx_post_unmap();
up_write(mm->bd_sem);
allocate_bounds_table();
That's the whole point of bd_sem.
> 3) According to Dave, those bounds tables related to adjacent VMAs within the
> start and the end possibly don't have to be fully unmmaped, and we only need
> free the part of backing physical memory.
Care to explain why that's a problem?
Thanks,
tglx
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next prev parent reply other threads:[~2014-10-27 20:49 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-12 4:41 [PATCH v9 00/12] Intel MPX support Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 01/12] x86, mpx: introduce VM_MPX to indicate that a VMA is MPX specific Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 02/12] x86, mpx: rename cfg_reg_u and status_reg Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 03/12] x86, mpx: add MPX specific mmap interface Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 04/12] x86, mpx: add MPX to disaabled features Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 05/12] x86, mpx: on-demand kernel allocation of bounds tables Qiaowei Ren
2014-10-24 12:08 ` Thomas Gleixner
2014-10-27 3:20 ` Ren Qiaowei
2014-10-28 17:43 ` Dave Hansen
2014-10-28 17:57 ` Thomas Gleixner
2014-10-12 4:41 ` [PATCH v9 06/12] mpx: extend siginfo structure to include bound violation information Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 07/12] mips: sync struct siginfo with general version Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 08/12] ia64: " Qiaowei Ren
2014-10-12 4:41 ` [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound violation information Qiaowei Ren
2014-10-24 12:36 ` Thomas Gleixner
2014-10-27 1:43 ` Ren, Qiaowei
2014-10-27 20:36 ` Thomas Gleixner
2014-10-28 5:58 ` Ren Qiaowei
2014-10-31 20:16 ` Dave Hansen
2014-10-31 20:33 ` Thomas Gleixner
2014-10-30 22:38 ` Dave Hansen
2014-10-31 2:12 ` Ren Qiaowei
2014-10-31 9:09 ` Thomas Gleixner
2014-10-12 4:41 ` [PATCH v9 10/12] x86, mpx: add prctl commands PR_MPX_ENABLE_MANAGEMENT, PR_MPX_DISABLE_MANAGEMENT Qiaowei Ren
2014-10-24 12:49 ` Thomas Gleixner
2014-10-24 15:10 ` Thomas Gleixner
2014-10-27 2:17 ` Ren, Qiaowei
2014-10-27 20:38 ` Thomas Gleixner
2014-10-28 5:57 ` Ren Qiaowei
2014-10-12 4:41 ` [PATCH v9 11/12] x86, mpx: cleanup unused bound tables Qiaowei Ren
2014-10-24 14:40 ` Thomas Gleixner
2014-10-27 3:13 ` Ren Qiaowei
2014-10-27 20:49 ` Thomas Gleixner [this message]
2014-10-28 5:56 ` Ren Qiaowei
2014-10-28 10:42 ` Thomas Gleixner
2014-11-03 20:53 ` Dave Hansen
2014-11-03 21:29 ` Thomas Gleixner
2014-11-04 16:00 ` Dave Hansen
2014-11-04 17:02 ` Thomas Gleixner
2014-11-06 21:50 ` Dave Hansen
2014-11-11 18:27 ` Thomas Gleixner
2014-11-11 20:44 ` Dave Hansen
2014-11-11 21:36 ` Thomas Gleixner
2014-10-12 4:41 ` [PATCH v9 12/12] x86, mpx: add documentation on Intel MPX Qiaowei Ren
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