lkml.org 
[lkml]   [2015]   [Sep]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops
Date
Setting CONFIG_PARAVIRT=y has an unintended side effect: it silently
turns all rdmsr and wrmsr operations into the safe variants without
any checks that the operations actually succeed.

This is IMO awful: it papers over bugs. In particular, KVM gueests
might be unwittingly depending on this behavior because
CONFIG_KVM_GUEST currently depends on CONFIG_PARAVIRT. I'm not
aware of any such problems, but applying this series would be a good
way to shake them out.

Fix it so that the MSR operations work the same on CONFIG_PARAVIRT=n
and CONFIG_PARAVIRT=y as long as Xen isn't being used. The Xen
maintainers are welcome to make a similar change on top of this.

Since there's plenty of time before the next merge window, I think
we should apply and fix anything that breaks.

Doing this is probably a prerequisite to sanely decoupling
CONFIG_KVM_GUEST and CONFIG_PARAVIRT, which would probably make
Arjan and the rest of the Clear Containers people happy :)

Andy Lutomirski (3):
x86/paravirt: Add _safe to the read_msr and write_msr PV hooks
x86/paravirt: Add paravirt_{read,write}_msr
x86/paravirt: Make "unsafe" MSR accesses unsafe even if PARAVIRT=y

arch/x86/include/asm/paravirt.h | 45 +++++++++++++++++++++--------------
arch/x86/include/asm/paravirt_types.h | 12 +++++++---
arch/x86/kernel/paravirt.c | 6 +++--
arch/x86/xen/enlighten.c | 27 +++++++++++++++++++--
4 files changed, 65 insertions(+), 25 deletions(-)

--
2.4.3



\
 
 \ /
  Last update: 2015-09-17 02:01    [W:0.150 / U:0.096 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site