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Re: [Qemu-devel] [PATCH v4 3/3] i386: publish advised value of MSR_IA32_

From: Raj, Ashok
Subject: Re: [Qemu-devel] [PATCH v4 3/3] i386: publish advised value of MSR_IA32_FEATURE_CONTROL via fw_cfg
Date: Fri, 17 Jun 2016 13:21:18 -0700
User-agent: Mutt/1.5.21 (2010-09-15)

On Fri, Jun 17, 2016 at 07:31:08PM +0200, Laszlo Ersek wrote:
> >>
> >> On 16/06/2016 08:06, Haozhong Zhang wrote:
> >>> It's a prerequisite that certain bits of MSR_IA32_FEATURE_CONTROL should
> >>> be set before some features (e.g. VMX and LMCE) can be used, which is
> >>> usually done by the firmware. This patch adds a fw_cfg file
> >>> "etc/msr_feature_control" which contains the advised value of
> >>> MSR_IA32_FEATURE_CONTROL and can be used by guest firmware (e.g. SeaBIOS).
> >>>

I'm sorry i'm joining this discussion a bit late returning from vacation. 
In a real platform supporting LMCE, BIOS is responsible for setting the bits 
for IA32_FEATURE_CONTROL correctly. There are good reasons why we want the 
BIOS to play this role.

in a virtualized environment, do we really have to push the same requirement
or would it suffice to just emulate it as we did in the early patches.

Not sure what exact problem is created by just simply supporting it within
kvm/qemu and not needing the bios for the guest to also adapt these changes.


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