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Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: A
From: |
Paolo Bonzini |
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 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 |
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.
- Re: [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set, (continued)
- Re: [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set, Eduardo Habkost, 2016/06/17
- Re: [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set, Paolo Bonzini, 2016/06/17
- Re: [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set, Eduardo Habkost, 2016/06/17
- Re: [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set, Paolo Bonzini, 2016/06/17
- Re: [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set, Eduardo Habkost, 2016/06/17
- [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Eduardo Habkost, 2016/06/21
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Paolo Bonzini, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Andrea Arcangeli, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set),
Paolo Bonzini <=
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Andrea Arcangeli, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Paolo Bonzini, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Andrea Arcangeli, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Michael S. Tsirkin, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Andrea Arcangeli, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Michael S. Tsirkin, 2016/06/22
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Gerd Hoffmann, 2016/06/23
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Michael S. Tsirkin, 2016/06/23
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Gerd Hoffmann, 2016/06/24
- Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set), Michael S. Tsirkin, 2016/06/24