linux-kernel - Re: [patch 2/4] x86/kaiser: Enable PARAVIRT again

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Date:   Tue, 28 Nov 2017 07:47:25 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>, daniel.gruss@...k.tugraz.at,
        hughd@...gle.com, keescook@...gle.com, linux-mm@...ck.org,
        michael.schwarz@...k.tugraz.at, moritz.lipp@...k.tugraz.at,
        richard.fellner@...dent.tugraz.at,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [patch 2/4] x86/kaiser: Enable PARAVIRT again

On 27/11/17 21:34, Thomas Gleixner wrote:
> XEN_PV paravirtualizes read/write_c3. This does not work with KAISER as the
> CR3 switch from and to user space PGD would require to map the whole XEN_PV
> machinery into both. It's also not clear whether the register space is
> sufficient to do so. All other PV guests use the native implementations and
> are compatible with KAISER.
> 
> Add detection for XEN_PV and disable KAISER in the early boot process when
> the kernel is running as a XEN_PV guest.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen