On Thu, Nov 24, 2022, Yang Weijiang wrote:
Arch LBR MSR_ARCH_LBR_DEPTH and MSR_ARCH_LBR_CTL are queried byAbsolutely not. "there are a lot of them" isn't sufficient justification. If
userspace application before it wants to {save|restore} the Arch LBR
data. Other LBR related data MSRs are omitted here intentionally due
to lengthy list(32*3). Userspace can still use KVM_{GET|SET}_MSRS to
access them if necessary.
the MSRs need to be migrated, then KVM needs to report them. If the expectation
is that XSAVES will handle them, then KVM needs to take a dependency on XSAVES
when enabling arch LBRs.