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

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Borislav Petkov <bp@alien8.de>,
	Andy Lutomirski <luto@amacapital.net>,
	"H. Peter Anvin" <hpa@zytor.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	xen-devel <xen-devel@lists.xen.org>,
	David Vrabel <david.vrabel@citrix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
Date: Mon, 16 Nov 2015 15:48:37 -0500	[thread overview]
Message-ID: <564A4125.8000603@oracle.com> (raw)
In-Reply-To: <20151116202232.GC20137@pd.tnic>

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