[Resent after removing g...@char.us.oracle.com.] 2018-02-26 17:13-0500, Konrad Rzeszutek Wilk: > On Sat, Feb 24, 2018 at 01:52:26AM +0100, Paolo Bonzini wrote: > > Use the new MSR feature framework to expose the ARCH_CAPABILITIES MSR to > > userspace. This way, userspace can access the capabilities even if it > > does not have the permissions to read MSRs. > > ... That is good but could you expand a bit of why it would want this? > > I am 99% sure it is due to the lovely spectre_v2 mitigation but > could you include that in the commit message so that in say a year > folks would know what this is?
Userspace can currently get the MSR by creating a VCPU and reading its MSR_IA32_ARCH_CAPABILITIES, because it is set from the hardware MSR. I thought that "permissions to read MSRs" talked about hardware MSRs, so the purpose of this patch would be a better interface, but I don't see how if we keep the auto-setting on VCPU creation. Is this aimed towards userspaces that want nothing else from KVM than the MSR value? Thanks.
