On Fri, Jun 17, 2016 at 10:48:17PM +0200, Laszlo Ersek wrote: > On 06/17/16 22:21, Raj, Ashok wrote: > > 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. > > At the moment, my understanding of this feature is superficial, but the > mechanisms involved in it don't seem complex. I don't expect > difficulties implementing it, I just need the details that I asked for > spelled out for me. > > As to why we should be doing this in the guest firmware(s) -- "because > that's what happens on physical machines too" :) Following the phys > world to the letter in virt is not always a goal, but it's never wrong. But the guest bios does nothing like the BIOS in the real platform. for e.g. a real bios would have SMM handlers to work for implementing firmware first mechanisms before notifying the OS. None of these exist in the virtalized world. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
