From: Paolo Bonzini <pbonzini@redhat.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>,
Marcel Apfelbaum <marcel@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set)
Date: Wed, 22 Jun 2016 16:33:18 +0200 [thread overview]
Message-ID: <ef002b40-712a-00e8-a30a-00057929a56f@redhat.com> (raw)
In-Reply-To: <20160622142414.GI30202@redhat.com>
On 22/06/2016 16:24, Andrea Arcangeli wrote:
> Linux could not possibly crash instead if host phys bits > guest phys
> bits because it will never depend on GPF triggering if the must be
> zero bits of the guest pagetables are set. Linux won't ever try to set
> those bits and I'd be shocked if any other OS does.
Well, KVM does. It sets _all_ bits up to 51, not just one, but still we
have a counterexample.
The reason to do this is that you can distinguish a not-present from a
present-reserved page fault, and handle the present-reserved page fault
from a cache without having to walk the page tables.
Paolo
> So while not perfect emulation of the hardware, the risk with known OS
> should be zero.
next prev parent reply other threads:[~2016-06-22 14:33 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 17:12 [Qemu-devel] [PATCH 0/5] x86: Physical address limit patches Dr. David Alan Gilbert (git)
2016-06-16 17:12 ` [Qemu-devel] [PATCH 1/5] BIT_RANGE convenience macro Dr. David Alan Gilbert (git)
2016-06-16 17:23 ` Paolo Bonzini
2016-06-16 17:24 ` Dr. David Alan Gilbert
2016-06-16 18:01 ` Peter Maydell
2016-06-16 18:05 ` Paolo Bonzini
2016-06-20 14:11 ` Dr. David Alan Gilbert
2016-06-20 14:17 ` Peter Maydell
2016-06-16 17:12 ` [Qemu-devel] [PATCH 2/5] x86: Mask mtrr mask based on CPU physical address limits Dr. David Alan Gilbert (git)
2016-06-16 19:59 ` Eduardo Habkost
2016-06-17 8:23 ` Dr. David Alan Gilbert
2016-06-17 12:13 ` Paolo Bonzini
2016-06-16 17:12 ` [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask Dr. David Alan Gilbert (git)
2016-06-16 20:14 ` Eduardo Habkost
2016-06-17 7:47 ` Paolo Bonzini
2016-06-17 12:46 ` Eduardo Habkost
2016-06-17 13:01 ` Paolo Bonzini
2016-06-17 13:41 ` Eduardo Habkost
2016-06-17 14:25 ` Paolo Bonzini
2016-06-17 15:27 ` Eduardo Habkost
2016-06-17 15:29 ` Paolo Bonzini
2016-06-17 15:35 ` Eduardo Habkost
2016-06-17 13:51 ` Dr. David Alan Gilbert
2016-06-17 14:19 ` Paolo Bonzini
2016-06-17 8:53 ` Dr. David Alan Gilbert
2016-06-16 17:12 ` [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set Dr. David Alan Gilbert (git)
2016-06-16 17:26 ` Paolo Bonzini
2016-06-16 18:09 ` Eduardo Habkost
2016-06-16 20:24 ` Eduardo Habkost
2016-06-17 8:15 ` Dr. David Alan Gilbert
2016-06-17 8:43 ` Paolo Bonzini
2016-06-17 9:17 ` Gerd Hoffmann
2016-06-17 9:52 ` Igor Mammedov
2016-06-17 11:20 ` Gerd Hoffmann
2016-06-17 16:20 ` Laszlo Ersek
2016-06-17 16:07 ` Laszlo Ersek
2016-06-19 16:13 ` Marcel Apfelbaum
2016-06-20 10:42 ` Igor Mammedov
2016-06-20 11:13 ` Marcel Apfelbaum
2016-06-17 9:37 ` Dr. David Alan Gilbert
2016-06-17 9:54 ` Paolo Bonzini
2016-06-17 13:18 ` Eduardo Habkost
2016-06-17 13:38 ` Paolo Bonzini
2016-06-17 15:19 ` Eduardo Habkost
2016-06-17 15:28 ` Paolo Bonzini
2016-06-17 15:49 ` Eduardo Habkost
2016-06-21 19:44 ` [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set) Eduardo Habkost
2016-06-22 12:41 ` Paolo Bonzini
2016-06-22 14:24 ` Andrea Arcangeli
2016-06-22 14:33 ` Paolo Bonzini [this message]
2016-06-22 14:44 ` Andrea Arcangeli
2016-06-22 14:48 ` Paolo Bonzini
2016-06-22 15:02 ` Andrea Arcangeli
2016-06-22 22:44 ` Michael S. Tsirkin
2016-06-22 23:23 ` Andrea Arcangeli
2016-06-22 23:45 ` Michael S. Tsirkin
2016-06-23 8:40 ` Gerd Hoffmann
2016-06-23 16:38 ` Michael S. Tsirkin
2016-06-24 5:55 ` Gerd Hoffmann
2016-06-24 23:12 ` Michael S. Tsirkin
2016-06-29 16:42 ` Dr. David Alan Gilbert
2016-06-30 6:10 ` Gerd Hoffmann
2016-06-30 10:59 ` Dr. David Alan Gilbert
2016-06-30 16:14 ` Gerd Hoffmann
2016-06-30 17:12 ` Dr. David Alan Gilbert
2016-07-01 19:03 ` Dr. David Alan Gilbert
2016-06-22 22:40 ` Michael S. Tsirkin
2016-06-22 23:15 ` Andrea Arcangeli
2016-06-19 3:36 ` [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set Michael S. Tsirkin
2016-06-20 7:04 ` Paolo Bonzini
2016-06-17 14:24 ` Marcel Apfelbaum
2016-06-16 17:12 ` [Qemu-devel] [PATCH 5/5] x86: Set physical address bits based on host Dr. David Alan Gilbert (git)
2016-06-17 7:25 ` Igor Mammedov
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