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Subject: Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
To: Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@amacapital.net>,
        "H. Peter Anvin" <hpa@zytor.com>
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Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        xen-devel <xen-devel@lists.xen.org>,
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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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Date: Mon, 16 Nov 2015 15:48:37 -0500
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On 11/16/2015 03:22 PM, Borislav Petkov wrote:
> On Mon, Nov 16, 2015 at 12:11:11PM -0800, Andy Lutomirski wrote:
>
>> Are there really multiple feature bits for this stuff?  I'd like to
>> imagine that the entry code is all either Xen PV or native/PVH/PVHVM
>> -- i.e. I assumed that PVH works like native for all entries.


Almost. For PVH we will have a small stub to set up bootparams and such 
but then we jump to startup_{32|64} code.


> I just reacted to Boris' statement:
>
> "We don't currently have a Xen-specific CPU feature. We could, in
> principle, add it but we can't replace all of current paravirt patching
> with a single feature since PVH guests use a subset of existing pv ops
> (and in the future it may become even more fine-grained)."

Actually, nevermind this --- I was thinking about APIC ops and they are 
not pv ops.

Note though that there are other users of pv ops --- lguest and looks 
like KVM (for one op) use them too.

-boris