lkml.org 
[lkml]   [2018]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 1/3] KVM: x86: use native MSR ops for SPEC_CTRL
From
Date
On 22/02/2018 18:07, Konrad Rzeszutek Wilk wrote:
>> Having a paravirt indirect call in the IBRS restore path is not a
>> good idea, since we are trying to protect from speculative execution
>> of bogus indirect branch targets. It is also slower, so use
>> native_wrmsrl on the vmentry path too.
> But it gets replaced during patching. As in once the machine boots
> the assembler changes from:
>
> callq *0xfffflbah
>
> to
> wrmsr
>
> ? I don't think you need this patch.

Why not be explicit? According to the spec, PRED_CMD and SPEC_CTRL
should be passed down to the guest without interception so it's safe to
do this. On the other hand, especially with nested virtualization, I
don't think you can absolutely guarantee that the paravirt call will be
patched to rdmsr/wrmsr.

Paolo

\
 
 \ /
  Last update: 2018-02-23 10:38    [W:0.078 / U:1.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site