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

From Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups linux.kernel
Subject Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
Date 2015-11-16 21:40 +0100
Message-ID <qvyJc-3Ft-19@gated-at.bofh.it> (permalink)
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On 11/16/2015 02:03 PM, Andy Lutomirski wrote:
> It's still a waste of effort, though. Also, I'd eventually like the 
> number of places in Xen code in which rsp/esp is invalid to be exactly 
> zero, and this approach makes this harder or even impossible.

That's what PVH is going to do.



> Does PVH hook into the entry asm code at all?  I thought it was just
> boot code and drivers.

Not the current version --- it starts with xen_start_kernel(). But we 
are currently changing it and my plan is to have a small stub executed 
initially (to set bootparams and such) and then jump to startup_{32|64}().

>
> In any case, someone needs to do some serious review and cleanup on
> the whole paravirt op mess.  We have a bunch of paravirt ops that
> serve little purpose.
>
> The paravirt infrastructure is a bit weird, too: it seems to
> effectively have four states for each patch site.  There's:
>
> 1. The initial state, which is unoptimized and works on native.
> Presumably any of these that happen early also need to work, if
> slowly, on Xen.

Not on PV (and as of today, on PVH) --- we start directly from 
xen_start_kernel(). I.e.  from step 2.

>
> 2. The Xen state without text patching.  I'm not actually sure why
> this exists at all.  Are there pvops that need to switch too early for
> us to patch the text?

I don't think so.

-boris
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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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