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Subject: Re: [patch 2/4] x86/kaiser: Enable PARAVIRT again
References: <20171127203416.236563829@linutronix.de>
 <20171127204257.575052752@linutronix.de>
From: Juergen Gross <jgross@suse.com>
Message-ID: <3dd8ba26-aa52-9d8b-011c-24ff18ae2d56@suse.com>
Date: Tue, 28 Nov 2017 07:47:25 +0100
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To: Thomas Gleixner <tglx@linutronix.de>, LKML <linux-kernel@vger.kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>, Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>, Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, Rik van Riel <riel@redhat.com>, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, linux-mm@kvack.org, michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at, richard.fellner@student.tugraz.at, Boris Ostrovsky <boris.ostrovsky@oracle.com>

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@linutronix.de>

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


Juergen

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