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Date: Wed, 12 Mar 2014 16:06:45 -0700
From: "H. Peter Anvin" <hpa@linux.intel.com>
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To: Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>
CC: Stefani Seibold <stefani@seibold.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Dave Jones <davej@redhat.com>,
        Martin Runge <Martin.Runge@rohde-schwarz.com>,
        Andreas Brief <Andreas.Brief@rohde-schwarz.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v2] x86: Remove compat vdso support
References: <f23ea19270122375e8d2efe0646bbe6101c451b4.1394499629.git.luto@amacapital.net> <CALCETrXai1eS9FFC=EsxzSy51fMjgEh+zD6meDJiovLirPKf2Q@mail.gmail.com> <CA+55aFzB9jjOjxT=m=5t04L3JONe5HhEhuHUXtqDYREmEjQrgQ@mail.gmail.com> <531F365B.4060000@linux.intel.com> <CA+55aFxmkBnwDfKhX7h1qoJ3emD=+ugc3OLNDH79a1kGu7He1Q@mail.gmail.com> <531F3D02.30706@linux.intel.com> <CALCETrXt5=N7U-f1i+oCkbF5xqc0Qn8U_C9B47grcuEagAhDEA@mail.gmail.com> <CALCETrWCXY-hwZh2U4QPp0YeeGuPXFUrUuCn7h-5H+TvdXEq5Q@mail.gmail.com> <CA+55aFz+OfvtXLxg4CA4C6GPGh8F_aDuG6nnFFCCBpjTPLP1zA@mail.gmail.com> <1394613046.995.51.camel@wall-e.seibold.net> <CA+55aFyTCoipjhbAVCuhCgqb8JeSjGcmOU3xE6EFrjNpfspfqg@mail.gmail.com> <CA+55aFxc8Qp-4_+n=upd-ghzkxpjCyRpesm3P7xtWjDyBe9MCw@mail.gmail.com> <CA+55aFyhS5jCWcxuK4bXKEPh+8HWbPE+gy1m4N9B-2HyT48+QA@mail.gmail.com> <5320D3AB.5060002@linux.intel.com> <CA+55aFzC1Xy1VNF46Mj8V8CEc0tyVA76+631xZiF6nk3Gyvc-Q@mail.gmail.com> <CALCETrUGc5+CS8=sYvtkK967ZR833zu98rzRkEw_DX++1hL-BA@mail.gmail.com>
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On 03/12/2014 02:49 PM, Andy Lutomirski wrote:
> On Wed, Mar 12, 2014 at 2:46 PM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>> On Wed, Mar 12, 2014 at 2:37 PM, H. Peter Anvin <hpa@linux.intel.com> wrote:
>>>
>>> How would that deal with the legacy vsyscall case for x86-64?  Just rely
>>> on the "legacy vsyscall emulation" (which seems to have its own class of
>>> problems...)?
>>
>> It does?
>>
>> We *default* to emulation, and have for over two years now (since
>> v3.4).  If there are problems with it, we need to fix those.
> 
> Even in the non-default "vsyscall=native" case, the vsyscall pages
> just contains syscalls.  It does not need to access the vvar page, the
> hpet, or anything else that the vdso uses.
> 

Ah, right.  I let that detail slip the mind.

I do hear vsyscall=native still being used as a workaround for problems,
but yes, just making it call the kernel is fine, of course.

So yes, this does make it all better.

	-hpa