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Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit

From Borislav Petkov <bp@alien8.de>
Newsgroups linux.kernel
Subject Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
Date 2015-11-16 21:00 +0100
Message-ID <qvy6u-3b3-17@gated-at.bofh.it> (permalink)
References (1 earlier) <quvX3-4s4-1@gated-at.bofh.it> <quxPb-5G2-1@gated-at.bofh.it> <qv9Uu-4OJ-9@gated-at.bofh.it> <qvuPh-1bQ-33@gated-at.bofh.it> <qvxk7-2PK-31@gated-at.bofh.it>
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On Mon, Nov 16, 2015 at 11:03:22AM -0800, Andy Lutomirski wrote:

> ...
> The reader surely doesn't remember that this isn't guaranteed to be a
> swapgs instruction on native.  Using:
> 
> ALTERNATIVE "swapgs" "" X86_FEATURE_XENPV
> 
> would be safer (it would get rid of the SWAPGS_UNSAFE_STACK mess) and
> much clearer.  We could hide *that* behind a macro and no one would be
> confused.  (Well, they'd be confused by the fact that Xen PV handles
> gsbase very differently from native, but that has nothing to do with
> the macro.)
> 
> I think we could convert piecemeal, and I wonder if this new patch for
> 32-bit native on 4.4 (this is needed for 4.4, right?) would be a good
> starting point.  Borislav, what do you think?  Would you be okay with
> adding a Xen PV pseudofeature?

AFAICT, I'd prefer this becomes rather a jump label which gets enabled
on xen. Especially if a single pseudofeature might not be enough,
apprently...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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Thread

Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-16 17:30 +0100
  Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andy Lutomirski <luto@amacapital.net> - 2015-11-16 20:10 +0100
    Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Borislav Petkov <bp@alien8.de> - 2015-11-16 21:00 +0100
      Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andy Lutomirski <luto@amacapital.net> - 2015-11-16 21:20 +0100
        Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Borislav Petkov <bp@alien8.de> - 2015-11-16 21:30 +0100
          Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-16 21:50 +0100
            Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andy Lutomirski <luto@amacapital.net> - 2015-11-16 22:00 +0100
              Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andy Lutomirski <luto@amacapital.net> - 2015-11-16 22:10 +0100
                Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Joao Martins <joao.m.martins@oracle.com> - 2015-11-17 12:00 +0100
              Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Borislav Petkov <bp@alien8.de> - 2015-11-16 22:10 +0100
          Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit "H. Peter Anvin" <hpa@zytor.com> - 2015-11-16 23:00 +0100
            Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-17 15:50 +0100
              Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andy Lutomirski <luto@amacapital.net> - 2015-11-17 20:00 +0100
                Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andy Lutomirski <luto@amacapital.net> - 2015-11-17 20:20 +0100
                Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Borislav Petkov <bp@alien8.de> - 2015-11-17 20:30 +0100
                Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andrew Cooper <andrew.cooper3@citrix.com> - 2015-11-17 20:30 +0100
                Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andy Lutomirski <luto@amacapital.net> - 2015-11-17 20:40 +0100
                Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-17 20:40 +0100
                Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-17 20:40 +0100
                Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Andrew Cooper <andrew.cooper3@citrix.com> - 2015-11-17 20:20 +0100
    Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-16 21:40 +0100

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