On Wed, May 12, 2021 at 12:08:00PM +0200, Thomas Gleixner wrote: > From: Sean Christopherson <seanjc@xxxxxxxxxx> > > commit b6b4fbd90b155a0025223df2c137af8a701d53b3 upstream > > Initialize MSR_TSC_AUX with CPU node information if RDTSCP or RDPID is > supported. This fixes a bug where vdso_read_cpunode() will read garbage > via RDPID if RDPID is supported but RDTSCP is not. While no known CPU > supports RDPID but not RDTSCP, both Intel's SDM and AMD's APM allow for > RDPID to exist without RDTSCP, e.g. it's technically a legal CPU model > for a virtual machine. > > Note, technically MSR_TSC_AUX could be initialized if and only if RDPID > is supported since RDTSCP is currently not used to retrieve the CPU node. > But, the cost of the superfluous WRMSR is negigible, whereas leaving > MSR_TSC_AUX uninitialized is just asking for future breakage if someone > decides to utilize RDTSCP. > > [ tglx: Backport for 4.14/4.19 ] Now queued up, thanks! greg k-h
